Abrupt climate change. A large-scale change in the climate system that takes place over a few decades or less, persists (or is anticipated to persist) for at least a few decades and causes substantial disruptions in human and natural systems.

Abrupt climate change. A large-scale abrupt change in the climate system that takes place over a few decades or less, persists (or is anticipated to persist) for at least a few decades and causes substantial impacts in human and/or natural systems. See also Tipping point and Abrupt change.

Abrupt change. A change in the system that is substantially faster than the typical rate of the changes in its history.

Acclimatization. A change in functional or morphological traits occurring once or repeatedly (e.g., seasonally) during the lifetime of an individual organism in its natural environment. Through acclimatization the individual maintains performance across a range of environmental conditions. For a clear differentiation between findings in laboratory and field studies, the term acclimation is used in ecophysiology for the respective phenomena when observed in well-defined experimental settings. The term (adaptive) plasticity characterizes the generally limited scope of changes in phenotype that an individual can reach through the process of acclimatization.

Accumulation (of glaciers, ice sheets, or snow cover). All processes that add to the mass of a glacier, an ice sheet, or snow cover. The main process of accumulation is snowfall. Accumulation also includes deposition of hoar, freezing rain, other types of solid precipitation, gain of wind-blown snow, avalanching, and basal accumulation (often beneath floating ice).

Adaptation. In human systems, climate change adaptation is the process of adjustment to actual or expected climate and its effects, in order to moderate harm or exploit beneficial opportunities (IPCC Special Report 1.5C). There are various types of adaptation:

• Adaptation limits. The point at which an actor’s objectives (or system needs) cannot be secured from intolerable risks through adaptive actions.

o Hard adaptation limit: No adaptive actions are possible to avoid intolerable risks.

o Soft adaptation limit: Options may exist but are currently not available to avoid intolerable risks through adaptive action.

• Adaptation pathways. Planning approaches that focus on the sequence of events over time and the tipping points necessary to shift paths. Dynamic adaptation pathways policy pathways (DAPP) is a specific pathway approach.
• Anticipatory adaptation: Adaptation that takes place before impacts of climate change are observed; occasionally referred as proactive adaptation.
• Autonomous adaptation: Adaptation that does not constitute a conscious response to climate stimuli but is triggered by ecological changes in natural systems and by market or welfare changes in human systems.
• Ecosystem-based adaptation (EBA). The use of ecosystem management activities to increase the resilience and reduce the vulnerability of people and ecosystems to climate change.
• Evolutionary adaptation. The process whereby a species of population becomes better able to live in a changing environment, through the selection of heritable traits. Biologist usually distinguish evolutionary adaptation from acclimatization with the latter occurring within an organism’s lifetime.
• Incremental adaptation. Adaptation that maintains the essence and integrity of a system or process at a given scale. In some case, incremental adaptation can accrue to result in transformational adaptation. Incremental adaptation to change in climate are understood as extensions of actions and behavior that already reduce the losses or enhance the benefits of natural variations in extreme weather/ climate events.
• Options. The array of strategic and measures that are available and appropriate for addressing adaptation. They include a wide range of actions that can be categorized as structural, institutional, ecological or behavioral.
• Planned adaptation: Adaptation that is the result of deliberate policy decision, based on an awareness that conditions have changed or about to change and that action is required to return to, maintain, or achieve a desired state.
• Transformational adaptation. Adaptation that changes the fundamental attributes of a social-ecological system in anticipation of climate change and its impacts; and adaptation response that will be required in the face of a global failure to mitigate the causes of anthropogenic climate change and are characterized by system-wide change or changes across more than one system, by a focus on the future and long-term change, or by direct questioning of the effectiveness of existing systems, social injustices and power imbalances.

Adaptive capacity. The ability of a system to adjust to climate change (including climate variability and extremes) to moderate potential damages, to take advantage of opportunities, or to cope with the consequences. It is used to describe the various socioeconomic, structural, institutional and technological abilities of human system to produce adaptation measures.

Adaptive capacity. The ability of systems, institutions, humans and other organisms to adjust to potential damage, to take advantage of opportunities, or to respond to consequences. (IPCC, AR4, 2007).

Adaptation Fund. A Fund established under the Kyoto Protocol in 2001 and officially launched in 2007. The Fund finances adaptation projects and programes in developing countries that are Parties to the Kyoto Protocol. Financing comes mainly from sales of Certified Emissions Reductions (CERs) and a share of proceeds amounting to 2% of the value of CERs issued each year for Clean Development Mechanism (CDM) projects. The Adaptation Fund can also receive funds from government, private sector, and individuals. Adaptation limits. The point at which an actor’s objectives (or system needs) cannot be secured from intolerable risks through adaptive actions.

Adaptation pathway. An adaptation pathway is a planning approach addressing the uncertainty and challenges of climate change decision- making. It enables consideration of multiple possible futures and allows analysis/exploration of the robustness and flexibility of various options across those multiple futures.

Adaptation strategy. An adaptation strategy is a program, project or approach that has been developed to respond to anticipated climate change impacts in a specific area of potential concern.

Adaptation tipping point. An adaptation tipping point is reached when the magnitude of external change is such that a policy no longer can meet its objectives, and new actions are needed to achieve the objectives

Adaptive Management. Refers to the process of iteratively planning, implementing, and modifying strategies for managing resources in the face of climate uncertainty and climate change. Adaptive management involves adjusting approaches in response to observations of the negative effects of climate change in the system brought on by resulting feedback effects and other variables.

Advection. Transport of water or air along with its properties (temperature, chemical tracers, etc) by winds or currents. Regarding the general distinction between advection and convection, the former describes transport by large-scale motions of the atmosphere or ocean, while convection describes the predominantly vertical, locally induced motions.

Adverse side-effect. A negative effect that a policy or measure aimed at one objective has on another objective, thereby potentially reducing the net benefit to society or the environment. See also Trade-off, Co-benefit. (IPCC, AR4, 2007).

Aerosol. A suspension of airborne solid or liquid particles, with typical diameters between a few nanometers and a few micrometers and atmospheric lifetimes of up to several days in the troposphere and up to years in the stratosphere. The term aerosol, which includes both the particles and the suspending gas, is often used in this report in its plural form to mean ‘aerosol particles’. Aerosols may be of either natural or anthropogenic origin in the troposphere; stratospheric aerosol mostly stems from volcanic eruptions. Aerosols can cause an effective radiative forcing directly through scattering and absorbing radiation (aerosol–radiation interaction), and indirectly by acting as cloud condensation nuclei or ice nucleating particles that affect the properties of clouds (aerosol–cloud interaction), and upon deposition on snow- or ice-covered surfaces. Atmospheric aerosols may be emitted as primary particulate matter, and form within the atmosphere from gaseous precursors (secondary production). The main classes of aerosol chemical composition are sea salt, organic carbon, black carbon (BC), mineral species (mainly desert dust), sulphate, nitrate and ammonium. See also Short-lived climate forcers (SLCF).

Afforestation. Conversion to forest of land that historically has not contained forests.

Agreement. In this report, the degree of agreement within the scientific body of knowledge on a particular finding is assessed based on multiple lines of evidence (e.g., mechanistic understanding, theory, data, models, expert judgement) and expressed qualitatively (Mastandrea et al., 2010). (IPCC).

Agroecology. The science and practice of applying ecological concepts, principles and knowledge (i.e., the interactions of, and explanations for, the diversity, abundance and activities of organisms) to the study, design and management of sustainable agroecosystems. It includes the roles of human beings as a central organism in agroecology by way of social and economic processes in farming systems. Agroecology examines the roles and interactions among all relevant biophysical, technical and socioeconomic components of farming systems and their surrounding landscapes (IPBES, 2019).

Collective name for land-use systems and technologies where woody perennials (trees, shrubs, palms, bamboos, etc.) are deliberately used on the same land-management units as agricultural crops and/or animals, in some form of spatial arrangement or temporal sequence. In agroforestry systems there are both ecological and economical interactions between the different components. Agroforestry can also be defined as a dynamic, ecologically based, natural resource management system that, through the integration of trees on farms and in the agricultural landscape, diversifies and sustains production for increased social, economic and environmental benefits for land users at all levels (FAO, 2015a).

Air pollution. Degradation of air quality with negative effects on human health or the natural or built environment due to the introduction, by natural processes or human activity, into the atmosphere of substances (gases, aerosols) which have a direct (primary pollutants) or indirect (secondary pollutants) harmful effect. See also Short- lived climate forcers (SLCF).

Albedo. The proportion of sunlight (solar radiation) reflected by a surface or object, often expressed as a percentage. Clouds, snow and ice usually have high albedo; soil surfaces cover the albedo range from high to low; vegetation in the dry season and/or in arid zones can have high albedo, whereas photosynthetically active vegetation and the ocean have low albedo. The Earth’s planetary albedo changes mainly through changes in cloudiness, snow, ice, leaf area and land cover.

Anthropogenic. Resulting from or produced by human activities. (Greenhouse gasses, aerosols, burning fossil fuels, deforestation. livestock production, fertilization, waste management and industrial processes).

Anthropocene. A proposed new geological epoch resulting from significant human-driven changes to the structure and functioning of the Earth System, including the climate system. Originally proposed in the Earth System science community in 2000, the proposed new epoch is undergoing a formalization process within the geological community based on the stratigraphic evidence that human activities have changed the Earth System to the extent of forming geological deposits with a signature that is distinct from those of the Holocene, and which will remain in the geological record. Both the stratigraphic and Earth System approaches to defining the Anthropocene consider the mid-20th Century to be the most appropriate starting date (Steffen et al., 2016), although others have been proposed and continue to be discussed. The Anthropocene concept has already been informally adopted by diverse disciplines and the public to denote the substantive influence of humans on the Earth System.

Anthropogenic subsidence. Downward motion of the land surface induced by anthropogenic drivers (e.g., loading, extraction of hydrocarbons and/or groundwater, drainage, mining activities) causing sediment compaction or subsidence/deformation of the sedimentary sequence, or oxidation of organic material, thereby leading to relative sea level rise.

Arid zone. Areas where vegetation growth is severely constrained due to limited water availability. For the most part, the native vegetation of arid zones is sparse. There is high rainfall variability, with annual averages below 300 mm. Crop farming in arid zones requires irrigation.

Aridity. The state of a long-term climatic feature characterised by low average precipitation or available water in a region. Aridity generally arises from widespread persistent atmospheric subsidence or anticyclonic conditions, and from more localised subsidence in the lee side of mountains (adapted from Ogallo and Gbeckor-Kove, 1989). See also Drought

Atmosphere. The gaseous envelope surrounding the earth. The dry atmosphere consist mostly entirely of nitrogen (78.1% volume mixing ration) and oxygen (20.9% volume mixing ratio), together with a number of trace gases, such as argon (0.93% volume mixing ratio), helium and radioactively active greenhouse gases such as carbon dioxide (0.035% volume mixing ratio) and ozone. In addition, the atmosphere contains the greenhouse gas water vapeur, whose amounts are highly variable but typically around 1% volume mixing ratio. The atmosphere also contains clouds and aerosols.

Attribution. Attribution is defined as the process of evaluating the relative contributions of multiple causal factors to a change or event with an assessment of confidence.

Autonomous adaptation. Adaptation in response to experienced climate change and its effects, without planning explicitly or consciously focused on addressing climate change. It is also referred to as spontaneous adaptation.

Avalanche. A mass of snow, ice, earth or rocks, or a mixture of these, falling down a mountainside.

Behavioral change. In this report, behavioral change refers to alteration of human decisions and actions in ways that mitigate climate change and/or reduce negative consequences of climate change impacts.

Benthic. Occurring at the bottom of a body of water; related to benthos (NOAA, 2018). See also Benthos.

Benthos. The community of organisms living on the bottom or in sediments of a body of water (such as an ocean, a river or a lake). The ecological zone at the bottom of a body of water, including the sediment surface and some sub-surface layers, is known as the ‘benthic zone’.

Beta Diversity. The change in species composition between different areas (spatial turnover) or times (temporal turnover) due to habitat and environmental heterogeneity

Biodiversity. Biodiversity or biological diversity means the variability among living organisms from all sources including, among other things, terrestrial, marine and other aquatic ecosystems, and the ecological complexes of which they are part; this includes diversity within species, between species, and of ecosystems (UN, 1992). See also Ecosystem, Ecosystem services

Biodiversity Hotspots. Biodiversity hotspots are geographic areas exceptionally rich in species, ecologically distinct, and often contain geographically rare endemic species. They are thus priorities for nature conservation action.

Bioenergy. Energy derived from any form of biomass or its metabolic by-products. See also Biofuel, Biomass

Biofuel. A fuel, generally in liquid form, produced from biomass. Biofuels include bioethanol from sugarcane, sugar beet or maize, and biodiesel from canola or soybeans. See also Bioenergy

Biomass. Organic material excluding the material that is fossilised or embedded in geological formations. Biomass may refer to the mass of organic matter in a specific area (ISO, 2014). See also Bioenergy, Biofuel

Biome. Global-scale zones, generally defined by the type of plant life that they support in response to average rainfall and temperature patterns. For example, tundra, coral reefs or savannas (IPBES, 2019).

Biosphere (terrestrial and marine). The part of the earth system comprising all ecosystems and living organisms, in the atmosphere, on land (terrestrial biosphere) or in the oceans (marine biosphere), including derived dead organic matter, such as litter, soil organic matter and oceanic detritus.

Blue carbon. Biologically-driven carbon fluxes and storage in marine systems that are amenable to management. Coastal blue carbon focuses on rooted vegetation in the coastal zone, such as tidal marshes, mangroves and seagrasses. These ecosystems have high carbon burial rates on a per unit area basis and accumulate carbon in their soils and sediments. They provide many non-climatic benefits and can contribute to ecosystem-based adaptation. If degraded or lost, coastal blue carbon ecosystems are likely to release most of their carbon back to the atmosphere. There is current debate regarding the application of the blue carbon concept to other coastal and non-coastal processes and ecosystems, including the open ocean. See also Ecosystem services and Sequestration

Biodiversity. The variability among living organisms from all sources including, among other things, terrestrial, marine and other aquatic ecosystems, and the ecological complexes of which they are part. This includes diversity within species, between species, and of ecosystems.

Capacity Building. The process by which people, organizations and society systematically stimulate and develop their capacities over time to achieve social and economic goals, including through improvement of knowledge, skills, systems, and institutions is known as capacity development or capacity development is a concept that extends the term of capacity building to encompass all aspects of creating and sustaining capacity growth over time. It does not involve only learning and various types of training but also continuous efforts to develop institutions, political awareness, financial resources, technology systems and the wider social and cultural enabling environment.

Carbon dioxide (CO2). A naturally occurring gas, CO2 is also a by-product of burning fossil fuels (such as oil, gas and coal), of burning biomass, of land use changes (LUC) and of industrial processes (e.g., cement production). It is the principal anthropogenic greenhouse gas (GHG) that affects the Earth’s radiative balance. It is the reference gas against which other GHGs are measured and therefore has a Global Warming Potential (GWP) of 1.

Carbon dioxide (CO2) fertilization. The increase of plant photosynthesis and water-use efficiency in response to increased atmospheric carbon dioxide (CO2) concentration. Whether this increased photosynthesis translates into increased plant growth and carbon storage on land depends on the interacting effects of temperature, moisture and nutrient availability effects of temperature, moisture and nutrient availability.

Carbon dioxide removal (CDR). Anthropogenic activities removing carbon dioxide (CO2) from the atmosphere and durably storing it in geological, terrestrial, or ocean reservoirs, or in products. It includes existing and potential anthropogenic enhancement of biological or geochemical CO2 sinks and direct air carbon dioxide capture and storage (DACCS), but excludes natural CO2 uptake not directly caused by human activities. See also Afforestation

Carbon footprint. Measure of the exclusive total amount of emissions of carbon dioxide (CO2) that is directly and indirectly caused by an activity or is accumulated over the life stages of a product (Wiedmann and Minx, 2008).

Carbon stock. The quantity of carbon in a carbon pool.

Cascading impacts. Cascading impacts from extreme weather/climate events occur when an extreme hazard generates a sequence of secondary events in natural and human systems that result in physical, natural, social or economic disruption, whereby the resulting impact is significantly larger than the initial impact. Cascading impacts are complex and multi-dimensional, and are associated more with the magnitude of vulnerability than with that of the hazard (modified from Pescaroli & Alexander, 2015).

Catchment. Is the land area from which rainfall will ultimately contribute to the river discharge. TYhe catchment area of the Ganges, Brahmaputra and Meghna Rivers are 907×103km2, 583×103km2 and 65×103km2, respectively, of which only 8% lies in Bangladesh. More than 90% of the water that flows into the B. ay of Bengal enters Bangladesh through its borders with India (IWM, 2020)

Cold spell. A cold spell is a distinctive type of extreme atmospheric event that manifests as anomalous low-temperatures over consecutive days. Even during periods of global warming, extreme cold temperatures continue to increase, with a stronger tendency for cold spell occurrences in certain regions of the world.

Climate. in a narrow sense is usually defined as the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period for averaging these variables is 30 years, as defined by the World Meteorological Organization. The relevant quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description of the climate system.

Climate. In a narrow sense climate is usually defined as the average weather -or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities- over a period of time ranging from months to thousands or millions of years. The classical period for averaging these variables is 30 years, as defined by the World Meteorological Organization (WMO). The relevant quantities are most often surface variables such as temperature, precipitation and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. (IPCC 2021).

Climate anomaly. The change or the difference between the average climate over a period of several decades or more, and the climate during a particular month or season.

Climate change. A change in the state of the climate that can be identified by changes in the mean and/or variability of its properties, and that persist for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcing such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in the composition of the atmosphere or in land use. The Framework Convention on Climate Change (UNFCCC) in its article 1, defines climate change as ‘a change which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods. The UNFCCC makes a distinction between climate change attributable to human activities altering the atmospheric composition, and climate variability attributable to natural causes. Climate change thus refers to a change in climate over time, whether due to natural variability or as a result of human activity.

Climate change. Climate change refers to a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forces such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in atmospheric composition or land use. (NAP 2023-2050)

Climate change. A change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in the composition of the atmosphere or in land use. Note that the United Nations Framework Convention on Climate Change (UNFCCC), in its Article 1, defines climate change as: ‘a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods’. The UNFCCC thus makes a distinction between climate change attributable to human activities altering the atmospheric composition and climate variability attributable to natural causes. See also Climate variability, Detection, Attribution, and Ocean acidification. (IPCC 2021).

Climate change adaptation. An adjustment process to the actual or expected climate and its effects. In human systems, adaptation seeks to moderate harm or exploit beneficial opportunities. In natural systems, human intervention may facilitate adjustment to the expected climate and its effects.

Climate change commitment. The further change in temperature after the atmospheric composition is constant is referred to as the constant composition temperature commitment or climate change commitment. The constant emission commitment is the committed climate change that would result from keeping anthropogenic emissions constant and the zero-emission commitment is the climate change commitment when emissions are set to zero.

Climate Change Impacts. The effects of climate change on natural and human systems. Depending on the state of adaptation, one can distinguish between potential impacts and residual impacts:

• Potential impacts. All impacts that may occur given a projected change in climate, without considering adaptation.
• Residual impacts. The impacts of climate change that would occur after adaptation has taken place.

Climate change impacts. The effects on natural and human systems of extreme weather and climate events and of climate change. Impacts generally refer to effects on lives, livelihoods, health status, ecosystems, economic, social and cultural assets, services (including environmental) and infrastructure due to the interaction of climate changes or hazardous climate events occurring within a specific period and the vulnerability of an exposed society or system. (NAP 2023-2050)

Climate change mitigation. Climate change mitigation means avoiding and reducing emissions of heat-trapping greenhouse gases into the atmosphere to prevent the planet from warming to more extreme temperatures.

Climate change scenario. A plausible and often simplified representation of the future climate, based on an internally consistent set of climatological relationships that has been constructed for explicit use in investigating the potential consequences of anthropogenic climate change, often serving as an input to impact models.

Climate change trend. Changes in climate that show a similar direction over time. An observed/historic trend could be, for example, the later arrival of rainfall over the last five years. Projected trends give a possible future direction, e.g., decreasing rainfall in summer. If combined with a data range, such trends can help to devise adaptation measures.

Community‐Based Adaptation (CbA). Ideally, CBA is a community-led and -driven process. It is a partnership between institutions and communities rather than something done for and imposed upon local peoples. The processes of assessment, planning, intervention and evaluation must be participatory, including all sections of local society, and incorporating peoples’ diverse priorities, concerns, perspectives and cultures.

Coast. Coast The land near to the sea. The term ‘coastal’ can refer to that land (e.g., as in ‘coastal communities’), or to that part of the marine environment that is strongly influenced by land-based processes. Thus, coastal seas are generally shallow and near-shore. The landward and seaward limits of the coastal zone are not consistently defined, neither scientifically nor legally. Thus, coastal waters can either be considered as equivalent to territorial waters (extending 12 nautical miles / 22.2 km from mean low water), or to the full Exclusive Economic Zone, or to shelf seas, with less than 200 m water depth.

Coastal Erosion. Coastal erosion, sometimes referred to as shoreline retreat, occurs when a net loss of sediment or bedrock from the shoreline results in landward movement of the high-tide mark.

Climate data. Historical and real-time climate observations along with direct model outputs covering historical and future periods. Information about how these observation and models were generated (metadata) should accompany all climate data. Climate-Related Data is defined by the United Nations Economic Commission Europe as ‘environmental, social, and economic data on the human causes of climate change, the impacts of climate change on human and natural systems, and efforts to mitigate climate change or adapts to its consequences (UNECE, 2014). The World Meteorological Organization (WMO, 2016) defines climate-related data as:

• Meteorological, hydro- logical, cryosphere and oceanographic data.
• Climate metadata.
• Observations generated by numerical climate models.
• Output generated by numerical climate models
• Data derived from terrestrial and remotely senses observations, and
• Other related data.

Climate data is considered as big data because it comes in large volumes and in a variety of formats that make it difficult to manage the data effectively (WMO, 2016pp 48).

Climatic driver (Climate driver). A changing aspect of the climate system that influences a component of a human or natural system.

Climate Impact Assessment (CIA). The practice of identifying and evaluating, in monetary and/or in non-monetary terms, the effects of climate change on natural and human systems. Climate projections are used to identify how the climate is changing, and then the impact of those changes on (infrastructure) systems such as shelters, bridges, road and the river basin dynamics are assessed, through hydrologic or meteorological modelling for example. UNEP defines uses the term Environmental Impact Assessment (EIA) as a tool to identify the environmental, social and economic impacts of a project prior to decision-making. In general the assessment comprises the following steps (World Bank): (i) Hazard exposure of the project location and proposed interventions or project components, (ii) Potential impact that identifies the sensitivity of project location and proposed interventions to identified climate exposure and ability to cope, (iii) Adaptive capacity, how resilient are the resources of the project location; is resilient built into the proposed project interventions/components, and (iv) Project risk, taken together, what are the project location and proposed interventions vulnerable to, and to what extend?

Climate extreme (extreme weather or climate event). The occurrence of a value of a weather or climate variable above (or below) a threshold value near the upper (or lower) ends of the range of observed values of the variable.

By definition, the characteristics of what is called extreme weather may vary from place to place in an absolute sense. When a pattern of extreme weather persists for some time, such as a season, it may be classified as an extreme climate event, especially if it yields an average or total that is itself extreme (e.g., high temperature, drought, or heavy rainfall over a season). For simplicity, both extreme weather events and extreme climate events are referred to collectively as ‘climate extremes’.

Climate feedback. An interaction in which a perturbation in one climate quantity causes a change in a second and the change in the second quantity ultimately leads to an additional change in the first. A negative feedback is one in which the initial perturbation is weakened by the changes it causes; a positive feedback is one in which the initial perturbation is enhanced. The initial perturbation can either be externally forced or arise as part of internal variability.

Climate finance. There is no agreed definition of climate finance. The term ‘climate finance’ is applied to the financial resources devoted to addressing climate change by all public and private actors from global to local scales, including international financial flows to developing countries to assist them in addressing climate change. Climate finance aims to reduce net greenhouse gas emissions and/or to enhance adaptation and increase resilience to the impacts of current and projected climate change. Finance can come from private and public sources, channelled by various intermediaries, and is delivered by a range of instruments, including grants, concessional and non-concessional debt, and internal budget reallocations.

Climate Hazard. The potential occurrence of a natural or human-induced climate event or trend, or climate change impact, which may cause loss of life, injury or other health impacts as well as losses and damages to property, infrastructure, livelihoods, service provision and environmental resources.

Climate information. Information about the past, current state, or future of the climate system that is relevant for mitigation, adaptation and risk management. It may be tailored or “co-produced” for specific contexts, taking into account users’ needs and values.

Climate Model. A qualitative or quantitative representation of the climate system based on the physical, chemical and biological properties of its components, their interaction and feedback processes and accounting for some of its known properties. The climate system can be represented by models of varying complexity; that is, for for any one component or combination of components a spectrum or hierarchy of models can be identified, differing in such aspects as the number of spatial dimensions, the extent to which physical, chemical or biological processes are explicitly represented, or the levels at which empirical parametrisation are involved. There is an evolution towards more complex models with interactive chemistry and for operational purposes, including monthly, seasonal and inter-annual climate predictions.

Climate model (spectrum or hierarchy). A numerical representation of the climate system based on its physical, chemical and biological properties, interactions, feedback processes, and accounting for some of its known properties. Climate models are applied as a research tool to study and simulate the climate, and for operational purposes, including monthly, seasonal and interannual climate predictions. (NAP 2023-2050)

Climate model. A qualitative or quantitative representation of the climate system based on the physical, chemical and biological properties of its components, their interactions and feedback processes and accounting for some of its known properties. The climate system can be represented by models of varying complexity; that is, for any one component or combination of components a spectrum or hierarchy of models can be identified, differing in such aspects as the number of spatial dimensions, the extent to which physical, chemical or biological processes are explicitly represented, or the level at which empirical parametrizations are involved. There is an evolution towards more complex models with interactive chemistry and biology. Climate models are applied as a research tool to study and simulate the climate and for operational purposes, including monthly, seasonal and interannual climate predictions. See also Earth System Model (ESM). (IPCC 2021).

Climate Prediction. A climate prediction (or forecast) is the result of an attempt to estimate the actual evolution of the climate in the future (seasonal, inter-annual, or long-term timescales).

Climate prediction. A climate prediction or climate forecast is the result of an attempt to produce (starting from a particular state of the climate system) an estimate of the actual evolution of the climate in the future, for example, at seasonal, interannual, or decadal time scales. Because the future evolution of the climate system may be highly sensitive to initial conditions, such predictions are usually probabilistic in nature. ). (IPCC 2021).

Climate Projection. The calculated response of the climate system to emissions or concentration scenarios of greenhouse gases, often based on simulations by climate models. Climate projections critically depend on the emissions scenarios used and therefore on highly uncertain assumptions of future socioeconomic and technological development.

Climate projection. Simulated response of the climate system to a scenario of future emissions or concentrations of greenhouse gases (GHGs) and aerosols and changes in land use, generally derived using climate models. Climate projections depend on an emission / concentration / radiative forcing scenario, which is in turn based on assumptions concerning, for example, future socioeconomic and technological developments that may or may not be realized. (IPCC 2021).

Climate Proofing. (i) Refers to the explicit consideration and internalisation of the risks and opportunities that alternative climate change scenarios are likely to imply for the design, operation, and maintenance of infrastructure. In other words, integrating climate change risks and opportunities into the design, operation, and management of infrastructure; ii) Actions taken to lessens or perhaps eliminate, the potential negative impacts through the life cycle of a project of weather and climate variability and of climate change based on a CRA and CRM principles; iii) The process of climate proofing investment projects aims both at assessing the climate risk to a project’s future costs and benefits and at undertaking a technical and economic analysis of options to alleviate or mitigate those risks. (ADB, Guidelines for Climate Proofing, 2017; ADB references to Ebinger and Vergara, 2011, Climate impacts, World Bank).

Climate refugium. A climate refugium is a geographic area that has had a stable climate on evolutionary timescales, or that is projected to have a stable climate into the future. See also refugium

Climate resilience. The capacity of a socioecological system to cope with a hazardous climate event, responding or reorganizing in ways that maintain its essential function, identity and structure while also maintaining the capacity for adaptation, learning and transformation. (NAP 2023-2050)

Climate Resilient. can be generally defined as the capacity for a socio-ecological system to: (i) absorb stresses and maintain function in the face of external stresses imposed upon it by climate change and (ii) adapt, recognize and evolve into more desirable configurations that improve the sustainability of the (infrastructure) system, leaving it better prepared for future climate change impacts.

Climate‐resilient development. Climate-resilient development means ensuring that people, communities, businesses and other organizations are able to cope with current climate variability as well as adapt to future climate change, preserving development gains and minimizing damages. Climate-resilient development is about adding the consideration of climate impacts and opportunities to development decision-making to improve development outcomes, rather than implementing development activities in a completely new way.

Climate-resilient Infrastructure. Planned, designed, built and operated in a way that anticipates, prepares for, and adapts to changing climate conditions. It can also withstand, respond to, and recover rapidly from disruptions caused by these climate conditions. (OECD, 2018, p4)

Climate Risk. The potential for climate change impacts where something of value is at stake and where the outcome is uncertain, recognizing the diversity of values. Risk is often represented as the probability of occurrence of hazardous climate events or trends multiplied by the impacts if these events or trends occur. Risk results from the interaction of vulnerability and hazard.

Climate services. Climate services involve the provision of climate information in such a way as to assist decision-making. The service includes appropriate engagement from users and providers, is based on scientifically credible information and expertise, has an effective access mechanism, and responds to user needs (Hewitt et al. 2012).

Climate signal. Climate signals are defined as long-term trends and projections that carry the fingerprint of climate change. Examples of observable long-term trends linked to climate change include rising sea levels, an increase in the frequency of extreme precipitation events and warming sea surface temperatures.

Climate simulation ensemble. A group of parallel model simulations characterizing historical climate conditions, climate predictions, or climate projections. Variation of the results across the ensemble members may give an estimate of modelling-based uncertainty. Ensembles made with the same model but different initial conditions characterize the uncertainty associated with internal climate variability, whereas multi-model ensembles including simulations by several models also include the effect of model differences. Perturbed parameter ensembles, in which model parameters are varied in a systematic manner, aim to assess the uncertainty resulting from internal model specifications within a single model. Remaining sources of uncertainty unaddressed with model ensembles are related to systematic model errors or biases, which may be assessed from systematic comparisons of model simulations with observations wherever available.

Climate-smart agriculture (CSA). An approach to agriculture that aims to transform and reorient agricultural systems to effectively support development and ensure food security in a changing climate by: sustainably increasing agricultural productivity and incomes; adapting and building resilience to climate change; and reducing and/or removing greenhouse gas emissions, where possible (FAO, 2018).

Climate system. The global system consisting of five major components: the atmosphere, the hydrosphere, the cryosphere, the lithosphere and the biosphere and the interactions between them. The climate system changes in time under the influence of its own internal dynamics and because of external forcings such as volcanic eruptions, solar variations, orbital forcing, and anthropogenic forcings such as the changing composition of the atmosphere and land-use change.

Climate vulnerability. The degree to which a system is susceptible to, and unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude and rate of climate change and the variation to which a system is exposed, its sensitivity and its adaptive capacity.

Climate variability. Deviations of some climate variables from a given mean state (including the occurrence of extremes, etc.) at all spatial and temporal scales beyond that of individual weather events. Variability may be intrinsic, due to fluctuations of processes internal to the climate system (internal variability), or extrinsic, due to variations in natural or anthropogenic external forcing (forced variability).

Climate velocity. The speed at which isolines of a specified climate variable travel across landscapes or seascapes due to changing climate. For example, climate velocity for temperature is the speed at which isotherms move due to changing climate (km yr-1) and is calculated as the temporal change in temperature (°C yr-1) divided by the current spatial gradient in temperature (°C km-1). It can be calculated using additional climate variables such as precipitation or can be based on the climatic niche of organisms.

Climate-resilient development. in the WGII report climate-resilient development refers to the process of implementing greenhouse gas mitigation and adaptation measures to support sustainable development for all.

Concept of Climate Resilience Infrastructure. Resilient infrastructure is that which is located, planned, designed, procured, built, maintained, operated, and decommissioned in a way that considers existing and potential hazard risks and is able to anticipate, absorb, recover, prepare for, learn from, and adapt to changing conditions over its lifecycle. Resilient infrastructure is important to:

• Protect occupants and maintain well-being
• Reduce direct losses and minimize damage to structural and non-structural elements
• Reduce the indirect costs of disruption
• Minimize service disruption and cascading failures of facilities and services
• Promote disaster risk reduction
• Safeguard Investments
• Contribute to sustainable development
• Manage risk within the built environment

Contextual vulnerability (starting‐point vulnerability). A present inability to cope with external pressures or changes, such as changing climate conditions. Contextual vulnerability is a characteristic of social and ecological systems generated by multiple factors and processes.

Climate-resilient pathways. Iterative processes for managing change within complex systems in order to reduce disruptions and enhance opportunities associated with climate change.

Climate scenario. A plausible and often simplified representation of the future climate, based on an internally consistent set of climatological relationships that has been constructed for explicit use in investigating the potential consequences of anthropogenic climate change, often serving as input to impact models. Climate projections often serve as the raw material for constructing climate scenarios, but climate scenarios usually require additional information such as the observed current climate.

Climate Sensitivity. The change in the annual global mean surface temperature in response to a change in the atmospheric carbon dioxide concentration or other radiative forcing.

Climate Services. A service providing climate information in a way that assists decision-making by individuals in organizations. It requires appropriate engagement along with an effective access mechanism and must respond to user needs.

Climate system. The climate system is the highly complex system consisting of five major components: the atmosphere, the hydrosphere, the cryo-sphere, the lithosphere, and the biosphere, and the interactions among them. The climate system evolves in time under the influence of its own internal dynamics and because of external forces such as volcanic eruptions, solar variations, and anthropogenic forces such as the changing composition of the atmosphere and land use change.

Climate variability. Climate variability refers to variations in the mean state and other statistics (e.g., standard deviations, the occurrence of extremes, etc) of the climate on all spatial and temporal scales beyond those of individual weather events. Variability may be due to natural internal processes within the climate system (internal variability) or to variations in natural or anthropogenic external forcing (external variability).

Compound weather/climate events. The terms ‘compound events’, ‘compound extremes’ and ‘compound extreme events’ are used interchangeably in the literature and this report and refer to the combination of multiple drivers and/or hazards that contributes to societal and/or environmental risk (Zscheischler et al., 2018).

Coping capacity. The ability of people, institutions, organizations and systems to address, manage and overcome adverse climate conditions in the short to medium term by using available skills, values, beliefs, resources and opportunities.

Coping Mechanism. The use of available skills, resources and opportunities to address, manage and overcome adverse climate conditions, which aims to achieve the basic functioning of people, institutions, organizations and systems in the short to medium term.

Co-Produced. The process of understanding and/or developing actionable science through active collaboration between scientists and policymakers.

Coastal Processes. The movement of water, sand, and land in coastal settings. This includes storm surge, wave set-up, tides, climate cycles, and in some cases groundwater.

Community-led adaptation. Local, community-driven adaptation. Community-led adaptation focuses attention on empowering and promoting the adaptive capacity of communities. It is an approach that takes context, culture, knowledge, agency, and preferences of communities as strengths.

Coral bleaching. Loss of coral pigmentation through the loss of intracellular symbiotic algae (known as zooxanthellae) and/or loss of their pigments.

Coral reef. An underwater ecosystem characterized by structure-building stony corals. Warm-water coral reefs occur in shallow seas, mostly in the tropics, with the corals (animals) containing algae (plants) that depend on light and relatively stable temperature conditions. Cold-water coral reefs occur throughout the world, mostly at water depths of 50-500 m. In both kinds of reef, living corals frequently grow on older, dead material, predominantly made of calcium carbonate (CaCO3). Both warm and cold-water coral reefs support high biodiversity of fish and other groups, and are considered to be especially vulnerable to climate change.

Coupled Model Intercomparison Project (CMIP). A climate modelling activity from the World Climate Research Program (WCRP) which coordinates and archives climate model simulations based on shared model inputs by modelling groups from around the world. The CMIP3 multi-model data set includes projections using Special Report on Emissions Scenarios (SRES) scenarios. The CMIP5 data set includes projections using the Representative Concentration Pathways (RCP). The CMIP6 phase involves a suite of common model experiments as well as an ensemble of CMIP-endorsed Model Intercomparison Projects (MIPs).

Cryosphere. The components of the Earth System at and below the land and ocean surface that are frozen, including snow cover, glaciers, ice sheets, ice shelves, icebergs, sea ice, lake ice, river ice, permafrost and seasonally frozen ground.

Cultural Impacts. Impacts on material and ecological aspects of culture and the lived experience of culture, including dimensions such as identity, community cohesion and belonging, sense of place, worldview, values, perceptions, and tradition. Cultural impacts are closely related to ecological impacts, especially for iconic and representational dimensions of species and landscapes. Culture and cultural practices frame the importance and value of the impacts of change, shape the feasibility and acceptability of adaptation options, and provide the skills and practices that enable adaptation.

Decarbonization. Human actions to reduce carbon dioxide emissions from human activities.

Deforestation. Conversion of forest to non-forest. See also Afforestation and Reforestation.

Disaster. Severe alterations in the normal functioning of a community or a society due to hazardous physical events interacting with vulnerable social conditions, leading to widespread adverse human, material, economic, or environmental effects that require immediate emergency response to satisfy critical human needs and that may require external support for recovery.

Direct Access Entity (DAEs). Direct access entities are subnational, national or regional organizations nominated by developing country national designated authorities (NDAs) or focal points. Organizations nominated to become direct access entities may be eligible to receive GCF readiness support. This funding is designed to help organizations in developing countries prepare to become accredited entities as well as helping those already accredited to strengthen their organizational capacities.

Decision scaling. A decision-making process that informs planning processes and users a decision analytical framework to reveal the full range of climate information that is needed to best inform the decision at hand.

Detection. Detection of change is defined as the process of demonstrating that climate or a system affected by climate has changed in some defined statistical sense, without providing a reason for that change. An identified change is detected in observations if its likelihood of occurrence by chance due to internal variability alone is determined to be small, for example, <10%.Diatoms. Microscopic (2-200µm) unicellular photosynthetic algae that live in surface waters of lakes, rivers and oceans and form shells of opal. In the global ocean, marine diatom species distribution is primarily driven by nutrient availability. On regional scales, their species distribution in ocean sediment cores can be related to past sea surface temperatures.

Disaster. A ‘serious disruption of the functioning of a community or a society at any scale due to hazardous events interacting with conditions of exposure, vulnerability and capacity, leading to one or more of the following: human, material, economic and environmental losses and impacts’ (UNGA, 2016) See also Exposure, Hazard, Risk and Vulnerability.

Disaster management. Social processes for designing, implementing, and evaluating strategies, policies, and measures that promote and improve disaster preparedness, response, and recovery practices at different organizational and societal levels.

Disaster management. Social processes for designing, implementing, and evaluating strategies, policies, and measures that promote and improve disaster preparedness, response, and recovery practices at different organizational and societal levels. (IPCC 2021).

Disaster risk. The likelihood within a specific time period of disaster.

Disaster risk. The likelihood over a specified time period of severe alterations in the normal functioning of a community or a society due to hazardous physical events interacting with vulnerable social conditions, leading to widespread adverse human, material, economic, or environmental effects that require immediate emergency response to satisfy critical human needs and that may require external support for recovery. (IPCC 2021).

Disaster Risk Management (DRM). Processes for designing, implementing, and evaluating strategies, policies, and measures to improve the understanding of disaster risk, foster disaster risk reduction and transfer, and promote continuous improvement in disaster preparedness, response, and recovery practices, with the explicit purpose of increasing human security, well-being, quality of life, and sustainable development.

Disaster risk management (DRM). Processes for designing, implementing, and evaluating strategies, policies, and measures to improve the understanding of current and future disaster risk, foster disaster risk reduction and transfer, and promote continuous improvement in disaster preparedness, prevention and protection, response, and recovery practices, with the explicit purpose of increasing human security, wellbeing, quality of life, and sustainable development (SD). (IPCC 2021).

Disaster Risk Reduction (DRR). Denotes both a policy goal or objective, and the strategic and instrumental measures employed for anticipating future disaster risk; reducing existing exposure, hazard, or vulnerability; and improving resilience.

Disaster Risk Reduction (DRR). Denotes both a policy goal or objective, and the strategic and instrumental measures employed for anticipating future disaster risk; reducing existing exposure, hazard, or vulnerability; and improving resilience. (IPCC 2021).

Disaster risk reduction (DRR). Disaster risk reduction is aimed at preventing new and reducing existing disaster risks and managing residual risks, all of which contributes to strengthening resilience and therefore to the achievement of sustainable development. (NAP 2023-2050)

Downscaling. Is a method that derives local-to-regional-scale (10 to 100 kilometers) information from larger scale models or data analyses. There are two main methods: dynamical downscaling and empirical or statistical downscaling. The dynamical method uses the output of regional climate models, global models with variable spatial resolution, or high-resolution global models. The empirical or statistical methods develop statistical relationships that link large-scale atmospheric variables with local and regional climate variables.

Drainage. Artificial lowering of the soil water table (IPCC, 2013).

Driver. Any natural or human-induced factor that directly or indirectly causes a change in a system (adapted from MA, 2005). See also Climatic driver. (IPCC 2021).

Drought. Drought is a prolonged, continuous period of dry weather along with abnormally insufficient rainfall. It occurs when evaporation, transpiration and water demand exceed the amount of rainfall and water availability over a reasonable period of time. Drought impacts are diverse and may be broadly classified into economic, environmental and social impacts. Drought is a relative term, therefor drought must be viewed in terms of precipitation deficit. For example, shortage of precipitation during the growing season impinges on crop production or ecosystem function in general (due to soil moisture drought) and during the runoff and percolation season primarily affects water supplies (hydrological drought). Storage changes in soil-moisture and groundwater are also affected by increases in actual evapotranspiration in addition to reductions in precipitation. A period with an abnormal precipitation deficit is defined as a meteorological drought. A mega-drought is a very lengthy and pervasive drought, lasting much longer than normal, usually a decade or more.

Drought. An exceptional period of water shortage for existing ecosystems and the human population (due to low rainfall, high temperature, and/or wind).

Megadrought – A very lengthy and pervasive drought, lasting much longer than normal, usually a decade or more.

Hydrological drought –A period with large runoff and water deficits in rivers, lakes and reservoirs.

Agricultural and ecological drought -Agricultural and ecological drought (depending on the affected biome): a period with abnormal soil moisture deficit, which results from combined shortage of precipitation and excess evapotranspiration, and during the growing season impinges on crop production or ecosystem function in general.

Meteorological drought – A period with an abnormal precipitation deficit.

Dry spell. One form of drought is the interruption of the rainy season by a so-called dry spell. A dry spell can be defined as a sequence of dry days, including days with less than a threshold value of rainfall.

Early warning systems (EWS). The set of technical and institutional capacities to forecast, predict, and communicate timely and meaningful warning information to enable individuals, communities, managed ecosystems, and organisations threatened by a hazard to prepare to act promptly and appropriately to reduce the possibility of harm or loss. Dependent upon context, EWS may draw upon scientific and/or indigenous knowledge, and other knowledge types. EWS are also considered for ecological applications, e.g., conservation, where the organization itself is not threatened by hazard but the ecosystem under conservation is (e.g., coral bleaching alerts), in agriculture (e.g., warnings of heavy rainfall, drought, ground frost, and hailstorms) and in fisheries (e.g., warnings of storm, storm surge, and tsunamis) (UNISDR 2009; IPCC, 2012a).

Earth system model (ESM). A coupled atmosphere–ocean general circulation model (AOGCM) in which a representation of the carbon cycle is included, allowing for interactive calculation of atmospheric carbon dioxide (CO2) or compatible emissions. Additional components (e.g., atmospheric chemistry, ice sheets, dynamic vegetation, nitrogen cycle, but also urban or crop models) may be included.

Ecosystem. A functional unit consisting of living organisms, their non-living environment and the interactions within and between them. The components included in a given ecosystem and its spatial boundaries depend on the purpose for which the ecosystem is defined: in some cases, they are relatively sharp, while in others they are diffuse. Ecosystem boundaries can change over time. Ecosystems are nested within other ecosystems and their scale can range from very small to the entire biosphere. In the current era, most ecosystems either contain people as key organisms, or are influenced by the effects of human activities in their environment. See also Ecosystem services and Ecosystem Health

Ecosystem Health. Ecosystem health is a metaphor used to describe the condition of an ecosystem, by analogy with human health. Note that there is no universally accepted benchmark for a healthy ecosystem. Rather, the apparent health status of an ecosystem is judged on the ecosystems resilience to change, with details depending upon which metrics are employed in judging it, and which societal aspirations are driving the assessment. (Following IPBES 2019)

Ecosystem services. Ecological processes or functions having monetary or non-monetary value to individuals or society at large. These are frequently classified as (1) supporting services such as productivity or biodiversity maintenance, (2) provisioning services such as food or fiber, (3) regulating services such as climate regulation or carbon sequestration, and (4) cultural services such as tourism or spiritual and aesthetic appreciation. See also Ecosystem and Ecosystem Health (IPCC 2021).

Ecosystems Services. Ecological processes or functions having monetary or non-monetary value to individuals or society at large. These are frequently classified as (i) supporting services such as productivity or biodiversity maintenance, (ii) provisioning services such as food or fiber, (iii) regulating services such as climate regulation or carbon sequestration, and (iv) cultural services such as tourism or spiritual and aesthetic appreciation.

Ecosystem‐Based Adaptation (EBA). Ecosystem-based adaptation uses the range of opportunities for the sustainable management, conservation and restoration of ecosystems to provide services that enable people to adapt to the negative impacts of climate change. (NAP 2023-2050)

Ecosystems-Based adaptation, can be defined as the use of ecosystem services and biodiversity as part of an overall adaptation strategy to help people to adapt to the adverse effects of climate change. (CBD, 2009).

El Niño-Southern Oscillation (ENSO). The term El Niño was initially used to describe a warm-water current that periodically flows along the coast of Ecuador and Peru, disrupting the local fishery. It has since become identified with warming of the tropical Pacific Ocean east of the dateline. This oceanic event is associated with a fluctuation of a global-scale tropical and subtropical surface pressure pattern called the Southern Oscillation. This coupled atmosphere– ocean phenomenon, with preferred time scales of two to about seven years, is known as the El Niño- Southern Oscillation (ENSO). The warm and cold phases of ENSO are called El Niño and La Niña, respectively. ENSO is often measured by the surface pressure anomaly difference between Tahiti and Darwin and/or the sea surface temperatures in the central and eastern equatorial Pacific. This phenomenon has a great impact on the wind, sea surface temperature and precipitation patterns in the tropical Pacific. It has climatic effects throughout the Pacific region and in many other parts of the world through global teleconnections. See Section AIV.2.3 in Annex IV of the AR6 WGI report.

Emergence (of the Climate Signal). Emergence of a climate change signal or trend refers to when a change in climate (the ‘signal’) becomes larger than the amplitude of natural or internal variations (defining the ‘noise’), This concept is often expressed as a ‘signal-to-noise’ ratio and emergence occurs at a defined threshold of this ratio (e.g., S/N > 1 or 2). Emergence can refer to changes relative to a historical or modern baseline (usually at least 20 years long) and can also be expressed in terms of time (time of emergence) or in terms of a global warming level. Emergence is also used to refer to a time when we can expect to see a response of reducing greenhouse gas (GHG) emissions (emergence with respect to mitigation). Emergence can be estimated using observations and/or model simulations.

Emissions. Anthropogenic emissions: Emissions of greenhouse gases (GHGs), precursors of GHGs and aerosols caused by human activities. These activities include the burning of fossil fuels, deforestation, land use and land use changes (LULUC), livestock production, fertilization, waste management, and industrial processes. Fossil fuel emissions: Emissions of greenhouse gases (in particular carbon dioxide), other trace gases and aerosols resulting from the combustion of fuels from fossil carbon deposits such as oil, gas and coal. Non-CO2 emissions and radiative forcing: non-CO2 emissions included in this report are all anthropogenic emissions other than CO2 that result in radiative forcing. These include short-lived climate forcers, such as methane (CH4), some fluorinated gases, ozone (O3) precursors, aerosols or aerosol precursors, such as black carbon and Sulphur dioxide, respectively, as well as long-lived greenhouse gases, such as nitrous oxide (N2O) or other fluorinated gases. The radiative forcing associated with non-CO2 emissions and changes in surface albedo is referred to as non-CO2 radiative forcing.

Enabling conditions (for adaptation and mitigation options). Conditions that enhance the feasibility of adaptation and mitigation options. Enabling conditions include finance, technological innovation, strengthening policy instruments, institutional capacity, multi-level governance, and changes in human behavior and lifestyles.

Energy access. Access to clean, reliable and affordable energy services for cooking and heating, lighting, communications, and productive uses (with special reference to Sustainable Development Goal 7) (AGECC, 2010).

Energy efficiency. The ratio of output or useful energy or energy services or other useful physical outputs obtained from a system, conversion process, transmission or storage activity to the input of energy (measured as kWh kWh- 1, tonnes kWh-1 or any other physical measure of useful output like tonne-km transported). Energy efficiency is often described by energy intensity.

Energy security. The goal of a given country, or the global community as a whole, to maintain an adequate, stable and predictable energy supply. Measures encompass safeguarding the sufficiency of energy resources to meet national energy demand at competitive and stable prices and the resilience of the energy supply; enabling development and deployment of technologies; building sufficient infrastructure to generate, store and transmit energy supplies and ensuring enforceable contracts of delivery.

Energy system. The energy system comprises all components related to the production, conversion, delivery, and use of energy.

Environmental Impact Assessment: Process by which the environmental consequences of a proposed project or program are evaluated is known as environmental impact assessment. It is undertaken as an integral part of planning and decision making processes with a view to limiting or reducing the adverse impacts of the project or program. Environmental impact assessment is a policy tool that provides evidence and analysis of environmental impacts of activities from conception to decision-making. It is utilized extensively in national programming and project approval processes and for international development assistance projects. Environmental impact assessments should include detailed risk assessments and provide alternatives, solutions, or options to deal with identified problems.

Evaporation. The physical process by which a liquid (e.g., water) becomes a gas (e.g., water vapor).

Evapotranspiration. the combined processes through which water is transferred to the atmosphere from open water and ice surfaces, bare soil, and vegetation that make up the Earth’s surface.

Evidence. Data and information used in the scientific process to establish findings. In this report, the degree of evidence reflects the amount, quality and consistency of scientific/technical information on which the Lead Authors are basing their findings. See also Agreement, Confidence, Likelihood and Uncertainty

Exposure. Presence of people, livelihoods, species or ecosystems, environmental functions, services, and resources, infrastructure, or economic, social, or cultural assets in places and settings that could be adversely affected (IPCC AR5).

Exposure. The presence of people, livelihoods, species or ecosystems, environmental services and resources, infrastructure, or economic, social or cultural assets in places that are exposed to the negative effects of climate change, with the potential to be adversely affected. (NAP 2023-2050)

Externality/external cost/external benefit. Externalities arise from a human activity, when agents responsible for the activity do not take full account of the activity’s impact on others’ production and consumption possibilities, and no compensation exists for such impacts. When the impact is negative, they are external costs. When positive they are referred to as external benefits. See also co-benefits

Extreme weather event. Event that is rare at a particular place and time of the year. Definitions or ‘rare’ vary, but an extreme weather event would normally be as rare or rarer than the 10th or 90th percentile of the observed probability density function.

Extreme sea level (ESL). The occurrence of an exceptionally low or high local sea-surface height, arising from (a combination of) short term phenomena (e.g. storm surges, tides and waves). Relative sea-level changes affect extreme sea levels directly by shifting the mean water levels and indirectly by modulating the propagation of tides, waves and/or surges due to increased water depth. In addition, extreme sea levels can be influenced by changes in the frequency, tracks, or strength of weather systems and storms, or due to anthropogenically induced changes such as the modification of coastlines or dredging. In turn, changes in any or all of the contributions to extreme sea levels may lead to long term relative sea-level changes. Alternate expressions for ESL may be used depending on the processes resolved. Extreme Still Water Level (ESWL) refers to the combined contribution of relative sea-level change, tides and storm-surges. Wind-waves also contribute to coastal sea level via three processes: infragravity waves (lower frequency gravity waves generated by the wind waves); wave setup (time-mean sea-level elevation due to wave energy dissipation); and swash (vertical displacement up the shore-face induced by individual waves). Extreme Total Water Level (ETWL) is the ESWL plus wave setup. When considering coastal impacts, swash is also important, and Extreme Coastal Water Level (ECWL) is used. See also Sea level change (sea level rise/ sea level fall)

Extreme weather event. An event that is rare at a particular place and time of year. Definitions of ‘rare’ vary, but an extreme weather event would normally be as rare as or rarer than the 10th or 90th percentile of a probability density function estimated from observations. By definition, the characteristics of what is called extreme weather may vary from place to place in an absolute sense. See also Heatwave and Climate extreme

Extreme/ heavy precipitation event. An extreme/heavy precipitation event is an event that is of very high magnitude with a very rare occurrence at a particular place. Types of extreme precipitation may vary depending on its duration, hourly, daily or multi-days (e.g., 5 days), though all of them qualitatively represent high magnitude. The intensity of such events may be defined with block maxima approach such as annual maxima or with peak over threshold approach, such as rainfall above 95th or 99th percentile at a particular space.

Feasibility. In this report, feasibility refers to the potential for a mitigation or adaptation option to be implemented. Factors influencing feasibility are context-dependent, temporally dynamic, and may vary between different groups and actors. Feasibility depends on geophysical, environmental-ecological, technological, economic, socio-cultural and institutional factors that enable or constrain the implementation of an option. The feasibility of options may change when different options are combined, and increase when enabling conditions are strengthened. See also Enabling conditions (for adaptation and mitigation options)

Fire weather. Weather conditions conducive to triggering and sustaining wildfires, usually based on a set of indicators and combinations of indicators including temperature, soil moisture, humidity, and wind. Fire weather does not include the presence or absence of fuel load.

Flood. The overflowing of the normal confines of a stream or other water body, or the accumulation of water over areas that are not normally submerged. Floods can be caused by unusually heavy rain, for example during storms and cyclones. Floods include river (fluvial) floods, flash floods, urban floods, rain (pluvial) floods, sewer floods, coastal floods, and glacial lake outburst floods (GLOFs).

Flux. A movement (a flow) of matter (e.g., water vapor, particles), heat or energy from one place to another, or from one medium (e.g., land surface) to another (e.g., atmosphere).

Food. The overflowing of the normal confines of a stream or other body of water, or the accumulation of water over areas not normally submerged. Floods include river (fluvial) floods, flash floods, urban floods, pluvial floods, sewer floods, coastal floods and glacial lake outburst floods. The floods in Bangladesh are divided into monsoon river flood, flash flood, local rainfall flood and storm surge flood.

Food security. A situation that exists when all people, at all times, have physical, social and economic access to sufficient, safe and nutritious food that meets their dietary needs and food preferences for an active and healthy life. The four pillars of food security are availability, access, utilization and stability. The nutritional dimension is integral to the concept of food security {FAO, 2018/ 2009 #6619}.

Availability –Physical availability of food. Food availability addresses the supply side of food security and is determined by the levels of food production, stocks and net trade.

Access –Economic and/ or physical access to food. Economic access is determined by disposable income, food prices and the provision of and access to social support. Physical access is determined by the availability and quality of land and other infrastructure, property rights or the functioning of markets.

Utilization-The way in which the body uses the various nutrients in food. Individuals achieve sufficient energy and nutrient intake through good care and feeding practices, food preparation, diet diversity and intrahousehold distribution of food. Combined with biological utilization of the food consumed, energy and nutrient intake determine the nutrition status of individuals.

Stability– The stability of the other three dimensions over time. Even if individuals’ food intake is adequate today, they are still considered food-insecure if periodically they have inadequate access to food, risking deterioration of their nutrition status. Adverse weather conditions, political instability or economic factors (unemployment, rising food prices) may have an impact on individuals’ food security status.

Food system. All the elements (environment, people, inputs, processes, infrastructures, institutions, etc.) and activities that relate to the production, processing, distribution, preparation and consumption of food, and the output of these activities, including socio-economic and environmental outcomes (HLPE, 2017). [Note: Whilst there is a global food system (encompassing the totality of global production and consumption), each location’s food system is unique, being defined by that place’s mix of food produced locally, nationally, regionally or globally.]

Food-borne disease. Illnesses transmitted through consumption of unsafe or contaminated food, that contamination can come from a variety of sources, including contaminated water. (Adapted from UNEP, 2018).

Forest. A vegetation type dominated by trees. Many definitions of the term forest are in use throughout the world, reflecting wide differences in biogeophysical conditions, social structure and economics. See also Afforestation, Deforestation and Reforestation

[Note: For a discussion of the term forest in the context of National GHG inventories, see the 2006 IPCC Guidelines for National GHG Inventories and their 2019 Refinement, and information provided by the United Nations Framework Convention on Climate Change (IPCC 2006, 2019; UNFCCC, 2021a, 2021b).]

Forest degradation. A reduction in the capacity of a forest to produce ecosystem services such as carbon storage and wood products as a result of anthropogenic and environmental changes.

Forest line. The upper limit of the closed upper montane forest or forest at high latitudes. It is less elevated or less poleward than the tree line

Fossil fuels. Carbon-based fuels from fossil hydrocarbon deposits, including coal, oil, and natural gas.

Forcing. The driver of a change in the climate system, usually through an imbalance between the radiative energy received by and leaving the Earth’s surface.

Future projection. A projection is a potential future climate event, often computed with the aid of a model. Climate projections are simulations of the Earth’s climate in future decades (typically until 2100) based on assumed scenarios for the concentrations of greenhouse gases, aerosols and other atmospheric constituents that affect the planet’s radiative balance.

General Circulation Models (GCM). A GCM is a mathematical model of the general circulation of a planetary atmosphere or ocean. Equations of the model are the basis for complex computer programs commonly used for simulating the earth’s atmosphere or ocean. Atmospheric and ocean GCMs are key components of global climate change models along with sea ice, and land surface components. GCMs and global climate models are widely applied for weather forecasting, understanding the climate, and projecting climate change.

Geo-engineering. Refers to a broad set of methods and technologies that aim to deliberately alter the climate system in order to alleviate the impacts of climate change. Geo-engineering is different from weather modification and ecological engineering but the boundary is fuzzy (IPCC, 2012).

Global Warming: The gradual increase observed or projected in global surface temperature as one of the consequences of radioactive forcing caused by anthropogenic emissions is known as global warming.

Glacial lake outburst flood (GLOF) / Glacier Lake outburst. A sudden release of water from a glacier lake, including any of the following types – a glacier-dammed lake, a pro-glacial moraine-dammed lake or water that was stored within, under or on the glacier.

Glacier. A perennial mass of ice, and possibly firm and snow, originating on the land surface by accumulation and compaction of snow and showing evidence of past or present flow. A glacier typically gains mass by accumulation of snow and loses mass by ablation. Land ice masses of continental size (>50,000 km2) are referred to as ice sheets (Cogley et al., 2011).

Global change. A generic term to describe global scale changes in systems, including the climate system, ecosystems, and social-ecological systems.

Global mean sea level change. Global mean sea level (GMSL) change is the increase or decrease in the volume of the ocean divided by the ocean surface area. It is driven by changes in ocean density through temperature changes (global mean thermosteric sea level change) and changes in the ocean mass as a result of changes in the cryosphere or terrestrial water storage (barystatic sea level change).

Global mean surface air temperature (GSAT). Global average of near-surface air temperatures over land, oceans and sea ice. Changes in GSAT are often used as a measure of global temperature change in climate models. See also Global mean surface temperature (GMST).

Global mean surface temperature (GMST). Estimated global average of near-surface air temperatures over land and sea ice, and sea surface temperature (SST) over ice-free ocean regions, with changes normally expressed as departures from a value over a specified reference period. See also Global mean surface air temperature (GSAT).

Global monsoon. The global monsoon (GM) is a global-scale solstitial mode that dominates the annual variation of tropical and sub-tropical precipitation and circulation. The GM domain is defined as the area where the annual range of precipitation (local summer minus winter mean precipitation rate) is greater than 2.5 mm day-1, following on from the definition as in Kitoh et al. (2013).

Global warming. Global warming refers to the increase in global surface temperature relative to a baseline reference period, averaging over a period sufficient to remove interannual variations (e.g., 20 or 30 years). A common choice for the baseline is 1850–1900 (the earliest period of reliable observations with sufficient geographic coverage), with more modern baselines used depending upon the application. See also Climate Change and Climate variability

Greenhouse Effect. Greenhouse gases effectively absorb thermal infrared radiation, emitted by the Earth’s surface, by the atmosphere itself due to the same gases, and by clouds. Atmospheric radiation is emitted to all sides, including downward to the Earth’s surface. Thus, greenhouse gases trap heat within the surface-troposphere system. This is called the greenhouse effect. Thermal infrared radiation in the troposphere is strongly coupled to the temperature of the atmosphere at the altitude at which it is emitted. In the troposphere, the temperature generally decreases with height. Effectively, infrared radiation emitted to space originates from an altitude with a temperature of on average, –190C, in balance with the net incoming solar radiation, whereas the Earth’s surface is kept at a much higher temperature of on average, +140C. An increase in the concentration of greenhouse gases leads to an increased infrared opacity of the atmosphere, and therefore to an effective radiation into space from a higher altitude at a lower temperature. This causes a radioactive forcing that leads to an enhancement of the greenhouse effect, the so-called enhanced greenhouse effect.

Haor. A haor, is a wetland ecosystem in the northeastern part of Bangladesh which physically is a bowl or saucer shaped shallow depression, also known as backswamp (Mujib Climate…GoB, pp. 45).

Green Climate Fund (GCF). The Green Climate Fund was established by the 16th Session of the Conference of the Parties (COP) in 2010 as an operating entity of the financial mechanism of the United Nations Framework Convention on Climate Change (UNFCCC), in accordance with Article 11 of the Convention, to support projects, programs and policies and other activities in developing country Parties. The Fund is governed by a board and will receive guidance of the COP.

Greenhouse gases (GHG). Gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of radiation emitted by the Earth’s ocean and land surface, by the atmosphere itself, and by clouds. This property causes the greenhouse effect. Water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4) and ozone (O3) are the primary GHGs in the Earth’s atmosphere. Human-made GHGs include Sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs), chlorofluorocarbons (CFCs) and perfluorocarbons (PFCs); several of these are also O3-depleting (and are regulated under the Montreal Protocol).

Groundwater recharge. The process by which external water is added to the zone of saturation of an aquifer, either directly into a geologic formation that traps the water or indirectly by way of another formation.

Ice sheet. An ice body originating on land that covers an area of continental size, generally defined as covering >50,000 km2, and that has formed over thousands of years through accumulation and compaction of snow. An ice sheet flows outward from a high central ice plateau with a small average surface slope. The margins usually slope more steeply, and most ice is discharged through fast-flowing ice streams or outlet glaciers, often into the sea or into ice shelves floating on the sea. There are only two ice sheets in the modern world, one on Greenland and one on Antarctica. The latter is divided into the East Antarctic Ice Sheet (EAIS), the West Antarctic Ice Sheet (WAIS) and the Antarctic Peninsula ice sheet. During glacial periods, there were other ice sheets.

Impacts. The consequences of realised risks on natural and human systems, where risks result from the interactions of climate-related hazards (including extreme weather / climate events), exposure, and vulnerability. Impacts generally refer Habitability (human). The ability of a place to support human life by providing protection from hazards which challenge human survival, and by assuring adequate space, food and freshwater.

Hazard. The potential occurrence of a natural or human-induced physical event or trend that may cause loss of life, injury, or other health impacts, as well as damage and loss to property, infrastructure, livelihoods, service provision, ecosystems and environmental resources. See also Impacts and Risk. (IPCC 2021).

Hazard. The potential concurrence of a natural or human-induced phenomenon (punctual) or trend (continuous), that may result in the loss of life, injury or other health impacts, as well as damage to and loss of property, infrastructure, livelihoods, services, ecosystems and environmental resources (IPCC AR5). Adverse situations that an area may face and that affect the day-to-day lives of inhabitants and normal development. With reference to climate change, these include droughts, floods, heatwaves, etc. (GIZ).

Hard adaptation limit. No adaptive actions are possible to avoid intolerable risks.

Heat index. A measure of how hot the air feels to the human body. The index is mainly based on surface air temperature and relative humidity; thus, it reflects the combined effect of high temperature and humidity on human physiology and provides a relative indication of potential health risks. See also Heatwave

Heat stress. A range of conditions in, for example, terrestrial or aquatic organisms when the body absorbs excess heat during overexposure to high air or water temperatures or thermal radiation. In aquatic water-breathing animals, hypoxia and acidification can exacerbate vulnerability to heat. Heat stress in mammals (including humans) and birds, both in air, is exacerbated by a detrimental combination of ambient heat, high humidity and low wind speeds, causing regulation of body temperature to fail.

Heat wave. There is no universally accepted definition, but it is understood that heat waves are understood to be periods of unusually hot and dry or hot and humid weather that have a subtle onset and cessation, a duration of at least 2-3 days, usually with a discernible impact on human and natural systems. Because there is no absolute universal value, such as a given temperature that defines what is extreme heat, heatwaves are relative to a location’s climate: the same meteorological conditions can constitute a heatwave in one place but not in another.

Heatwave. A period of abnormally hot weather often defined with reference to a relative temperature threshold, lasting from two days to months. Heatwaves and warm spells have various and, in some cases, overlapping definitions. See also Heat index, Heat stress and Marine Heatwave. (IPCC 2021).

Human behavior. The responses of persons or groups to a particular situation, here likely to relate to climate change. Human behavior covers the range of actions by individuals, communities, organizations, governments and at the international level.

• Adaptation behavior. Human actions that directly or indirectly affects the risks of climate change impacts.
• Mitigation behavior. Human actions that directly or indirectly influence mitigation.

Hydrological Cycle. The cycle in which water evaporates from the oceans and the land surface, is carried over the Earth in atmospheric circulation as water vapor, condense s to form clouds, precipitates over ocean and land as rain or snow, which on land can be intercepted by trees and vegetation, provides runoff on the land surface, infiltrates into soils, recharges groundwater, discharges into streams and ultimately flows out into the oceans, from which it will eventually evaporate again. The various systems involved in the hydrological cycle are usually referred to as hydrological systems.

Hydrological cycle. The cycle in which water evaporates from the ocean and the land surface, is carried over the Earth in atmospheric circulation as water vapour, condenses to form clouds, precipitates over the ocean and land as rain or snow, which on land can be intercepted by trees and vegetation, potentially accumulating as snow or ice, provides runoff on the land surface, infiltrates into soils, recharges groundwater, discharges into streams, and ultimately, flows into the oceans as rivers, polar glaciers and ice sheets, from which it will eventually evaporate again. The various systems involved in the hydrological cycle are usually referred to as hydrological systems. (IPCC 2021).

Hydropower. Power harnessed from the flow of water.

Hyperthermal Event. Geologically abrupt global warming events of the past associated with disturbances of the carbon cycle and impacts on the biosphere.

Hypoxic. Conditions of low dissolved oxygen in shallow water ocean and freshwater environments. There is no universal threshold for hypoxia. A value around 60 μmol kg-1 has commonly been used for some estuarine systems, although this does not necessarily directly translate into biological impacts. Anoxic conditions occur where there is no oxygen present at all. See also Eutrophication.

Hypoxic events. Events that lead to deficiencies of oxygen in water bodies.

Hydropower. Power harnessed from the flow of water.

Hyperthermal Event. Geologically abrupt global warming events of the past associated with disturbances of the carbon cycle and impacts on the biosphere.

Hypoxic. Conditions of low dissolved oxygen in shallow water ocean and freshwater environments. There is no universal threshold for hypoxia. A value around 60 μmol kg-1 has commonly been used for some estuarine systems, although this does not necessarily directly translate into biological impacts. Anoxic conditions occur where there is no oxygen present at all. See also Eutrophication.

Hypoxic events. Events that lead to deficiencies of oxygen in water bodies.

To effects on lives, livelihoods, health and wellbeing, ecosystems and species, economic, social and cultural assets, services (including ecosystem services), and infrastructure. Impacts may be referred to as consequences or outcomes, and can be adverse or beneficial. See also Adaptation, Exposure, Loss and Damage and losses and damages, Vulnerability and Risk

Integrated Coastal Zone Management. An integrated approach for sustainably managing coastal areas, considering all coastal habitats and uses.

Infrastructure. The designed and built set of physical systems and corresponding institutional arrangements that mediate between people, their communities, and the broader environment to provide services that support economic growth, health, quality of life, and safety (Chester, 2019; Dawson et al., 2018) There are four categories of infrastructure:

• Blue infrastructure- blue infrastructure includes bodies of water, watercourses, ponds, lakes and storm drainage, that provide ecological and hydrological functions including evaporation, transpiration, drainage, infiltration, and temporarily storage of runoff and discharge.
• Green infrastructure – The strategically planned interconnected set of natural and constructed ecological systems, green spaces and other landscape features that can provide functions and services including air and water purification, temperature management, floodwater management and coastal defense often with co- benefits for human and ecological well-being. Green infrastructure includes planted and remnant native vegetation, soils, wetlands, parks and green open spaces, as well as building and street level design interventions that incorporate vegetation. (After Culwick and Bobbins, 2016)
• Grey infrastructure – Engineered physical components and networks of pipes, wires, roads, tracks that underpin energy, transport, communications (including digital), built form, water and sanitation and solid waste management systems.
• Social infrastructure – The social, cultural, and financial activities and institutions as well as associated property, buildings and artefacts and policy domains such as social protection, health and education that support wellbeing and public life. (Frolova et al., 2016; Latham and Layton, 2019).

Integrated assessment model (IAM). Models that integrate knowledge from two or more domains into a single framework. They are one of the main tools for undertaking integrated assessments. One class of IAM used in respect of climate change mitigation may include representations of: multiple sectors of the economy, such as energy, land use and land use change; interactions between sectors; the economy as a whole; associated greenhouse gas (GHG) emissions and sinks; and reduced representations of the climate system. This class of model is used to assess linkages between economic, social and technological development and the evolution of the climate system. Another class of IAM additionally includes representations of the costs associated with climate change impacts, but includes less detailed representations of economic systems. These can be used to assess impacts and mitigation in a cost-benefit framework and have been used to estimate the social cost of carbon.

Justice. Justice is concerned with ensuring that people get what is due to them, setting out the moral or legal principles of fairness and equity in the way people are treated, often based on the ethics and values of society.

Climate justice – Justice that links development and human rights to achieve a human-centered approach to addressing climate change, safeguarding the rights of the most vulnerable people and sharing the burdens and benefits of climate change and its impacts equitably and fairly (MRFJC, 2018).

Procedural justice – Justice in the way outcomes is brought about including who participates and is heard in the processes of decision-making.

Social justice – Just or fair relations within society that seek to address the distribution of wealth, access to resources, opportunity, and support according to principles of justice and fairness.

Key risk. Those risks that are especially relevant to the interpretation of ‘dangerous anthropogenic interference with the climate system’ (DAI) in the terminology of UNFCCC, Article 2, meriting particular attention by policy makers in that context. Key risks are potentially severe adverse consequences for humans and social- ecological systems resulting from the interaction of climate related hazards with vulnerabilities of societies and systems exposed. Risks are considered “key” due to high hazard or high vulnerability of societies and systems exposed, or both.

Knowledge Management. Is defined as generating, curating, organizing, sharing, and using knowledge and information to create value for LGED and support decision-making in context.

Land. The terrestrial portion of the biosphere that comprises the natural resources (soil, near-surface air, vegetation and other biota, and water), the ecological processes, topography, and human settlements and infrastructure that operate within that system (FAO, 2007; UNCCD, 1994).

Land cover. The biophysical coverage of land (e.g., bare soil, rocks, forests, buildings and roads or lakes). Land cover is often categorised in broad land-cover classes (e.g., deciduous forest, coniferous forest, mixed forest, grassland, bare ground). Note: In some literature assessed in this report, land cover and land use are used interchangeably, but the two represent distinct classification systems. For example, the land cover class woodland can be under various land uses such as livestock grazing, recreation, conservation, or wood harvest.

Land cover change. Change from one land cover class to another, due to change in land use or change in natural conditions (Pongratz et al., 2018). See also Land cover and Land-use change

Land degradation. A negative trend in land condition, caused by direct or indirect human-induced processes including anthropogenic climate change, expressed as long-term reduction or loss of at least one of the following: biological productivity, ecological integrity or value to humans. [Note: This definition applies to forest and non-forest land. Changes in land condition resulting solely from natural processes (such as volcanic eruptions) are not considered to be land degradation. Reduction of biological productivity or ecological integrity or value to humans can constitute degradation, but any one of these changes need not necessarily be considered degradation.]

Land management. Sum of land-use practices (e.g., sowing, fertilizing, weeding, harvesting, thinning, clear-cutting) that take place within broader land-use categories. (Pongratz et al., 2018)

Land use. The total of arrangements, activities and inputs applied to a parcel of land. The term land use is also used in the sense of the social and economic purposes for which land is managed (e.g., grazing, timber extraction, conservation and city dwelling). In national greenhouse gas (GHG) inventories, land use is classified according to the IPCC land-use categories of forest land, cropland, grassland, wetlands, settlements, other lands (see the 2006 IPCC Guidelines for National GHG Inventories and their 2019 Refinement for details (IPCC, 2021).

Land use and Land use change. Refers to the total of arrangements, activities and inputs undertaken in a certain land cover type (a set of human actions). The term land use is also used in the sense of the social and economic purposes for which land is managed (e.g., grazing, timber extraction and conservation). Land use change refers to a change in the use or management of land by humans, which may lead to a change in land cover. Land cover and land use change may have an impact on the surface albedo, evapotranspiration, sources and sinks of greenhouse gases, or other properties of the climate system and may thus give rise to radiative forcing and/or other impacts on climate, locally or globally. See also the IPCC Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000).

Land-use change. The change from one land use category to another. Note that in some scientific literature, land-use change encompasses changes in land-use categories as well as changes in land management. See also Afforestation, Agriculture, Forestry and Other Land Use (AFOLU), Deforestation, Land use, land-use change and forestry (LULUCF) and Reforestation.

Indirect land-use change (iLUC) –Land use change outside the area of focus, that occurs as a consequence of change in use or management of land within the area of focus, such as through market or policy drivers. For example, if agricultural land is diverted to biofuel production, forest clearance may occur elsewhere to replace the former agricultural production. See Land-use change (LUC).

Locally led adaptation (LLA). Locally led adaptation (LLA) can unlock, support and leverage the enormous potential and creativity of communities to develop and implement solutions. Shifting power to local stakeholders, without expecting them to shoulder the burdens of adaptation, can catalyze adaptation that is effective, equitable and transparent.

Lock-in. A situation in which the future development of a system, including infrastructure, technologies, investments, institutions, and behavioral norms, is determined or constrained (‘locked in’) by historic developments. See also Path dependence

Loss and Damage, and losses and damages. Research has taken Loss and Damage (capitalized letters) to refer to political debate under the United Nations Framework Convention on Climate Change (UNFCCC) following the establishment of the Warsaw Mechanism on Loss and Damage in 2013, which is to ‘address loss and damage associated with impacts of climate change, including extreme events and slow onset events, in developing countries that are particularly vulnerable to the adverse effects of climate change.’ Lowercase letters (losses and damages) have been taken to refer broadly to harm from (observed) impacts and (projected) risks and can be economic or non- economic. (Mechler et al., 2018).

Low-likelihood, high impact outcomes. Outcomes/events whose probability of occurrence is low or not well known (as in the context of deep uncertainty) but whose potential impacts on society and ecosystems could be high. To better inform risk assessment and decision-making, such low-likelihood outcomes are considered if they are associated with very large consequences and may therefore constitute material risks, even though those consequences do not necessarily represent the most likely outcome. See also impacts

Low‐regret policy. Refers to a policy that would generate net social and/or economic benefits under the current climate and a range of future climate change scenarios.

Likelihood. The chance of a specific outcome occurring, where this might be estimated probabilistically. Likelihood is expressed in this Special Report using a standard terminology (Mastrandrea et al., 2010). See also Agreement, Confidence, Evidence and Uncertainty

Livelihood. The resources used and the activities undertaken in order for people to live. Livelihoods are usually determined by the entitlements and assets to which people have access. Such assets can be categorized as human, social, natural, physical, or financial.

Mainstreaming. In the context of climate change and development, ‘mainstreaming’ refers broadly to calling attention to climate change concerns within development planning, considering how climate change might impact development goals and activities and, conversely, how these might positively or negatively affect vulnerability to climate change. International Red Cross/Crescent defines mainstreaming ‘considering and addressing risks associated with disasters and climate change in all processes of policy making, planning, budgeting, implementation, and monitoring’. In the context of LGED mainstreaming is the process of systematically integrating climate change in all phases of project planning, design and management. Mainstreaming can be facilitated through: (i) Policies, Strategies & Guidelines, (ii) Communication and training, (iii) Documenting and disseminating project implementation experiences, and (iv) Knowledge exchange processes. Mainstreaming takes place at national, subnational and local levels. In some cases, mainstreaming may also imply a cultural shift within the institution, so that consideration of climate risks and strategies become embedded in every-day decision-making (Parry, Talyor, UNEP, 2011).

Maladaptive actions (Maladaptation). Actions that may lead to increased risk of adverse climate-related outcomes, including via increased greenhouse gas (GHG) emissions, increased vulnerability to climate change, or diminished welfare, now or in the future. Maladaptation is usually an unintended consequence.

Maladaptive actions (maladaptation). Actions that may lead to an increased risk of adverse climate-related outcomes, increased vulnerability to climate change or diminished welfare, now or in the future. (NAP 2023-2050).

Maladaptive actions (Maladaptation). Actions that may lead to increased risk of adverse climate-related outcomes, including via increased greenhouse gas (GHG) emissions, increased or shifted vulnerability to climate change, more inequitable outcomes, or diminished welfare, now or in the future. Most often, maladaptation is an unintended consequence. (IPCC 2021).

Marine heatwave. A period during which water temperature is abnormally warm for the time of the year relative to historical temperatures, with that extreme warmth persisting for days to months. The phenomenon can manifest in any place in the ocean and at scales of up to thousands of kilometers. See also Heatwave

Mean sea level. The surface level of the ocean at a particular point averaged over an extended period of time such as a month or year. Mean sea level is often used as a national datum to which heights on land are referred.

Methane (CH4). One of the six greenhouse gases (GHGs) to be mitigated under the Kyoto Protocol. Methane is the major component of natural gas and associated with all hydrocarbon fuels. Significant anthropogenic emissions also occur as a result of animal husbandry and paddy rice production. Methane is also produced naturally where organic matter decays under anaerobic conditions, such as in wetlands. Under future global warming, there is risk of increased methane emissions from thawing permafrost, coastal wetlands and sub-sea gas hydrates. See also Short-lived climate forcers (SLCFs).

Microclimate. Local climate at or near the Earth’s surface.

Mitigation (of climate change). A human intervention to reduce the sources or enhance the sinks of greenhouse gases and/or the lessening of the potential adverse impacts of physical hazards (including those that are human induced) through actions that reduce hazard, exposure, and vulnerability.

Mitigation (of climate change). A human intervention to reduce emissions or enhance the sinks of greenhouse gases.

Mitigation measures. In climate policy, mitigation measures are technologies, processes or practices that contribute to mitigation, for example renewable energy technologies, waste minimization processes, and public transport commuting practices.

Mitigation option. A technology or practice that reduces greenhouse gas (GHG) emissions or enhances sinks.

Mitigation scenario. A plausible description of the future that describes how the (studied) system responds to the implementation of mitigation policies and measures.

Monitoring and evaluation (M&E). Mechanisms put in place to respectively monitor and evaluate efforts to reduce greenhouse gas emissions and/or adapt to the impacts of climate change with the aim of systematically identifying, characterizing and assessing progress over time.

Mountains. A mountain is a landform formed through plate tectonics that rises above its surrounding area, characterized by verticality and ruggedness such as gentle or steep sloping sides, sharp or rounded ridges, and a high point called a peak or a summit. Mountain regions consist of mountains and mountain ranges as defined by ruggedness, intermontane valleys, plateaus and tablelands, and hills and hilly forelands, together forming a complex terrain.

To delineate mountain regions a combination of terrain characteristics is used, such as elevation above sea level, steepness of slope and relative relief or local elevational range.

Three mountain characterizations using different combinations of the above criteria applied to digital elevation models have been developed to arrive at mountain area statistics, described and analysed in detail in Sayre et al, (2018), namely K1 (Kapos et al., 2000), K2 (Körner et al., 2011) and K3 (Karagulle et al., 2017).

National designated authority (NDA). National designated authorities (NDAs) are government institutions that serve as the interface between a country and the GCF. They provide broad strategic oversight of the GCF’s activities in the country and communicate the country’s priorities for financing low-emission and climate- resilient development. In November 2014, the Economics Relations Division (ERD) under the MoF was nominated by the Government of Bangladesh to be the national designated authority (NDA) to the Green Climate Fund (GCF).

Nationally Determined Contributions (NDC). A term used under the UNFCCC whereby a country that has joined the Paris Agreements outlines its plans for reducing its emissions.

National implementing entity (NIE). National implementing entities (NIE) are accredited entities that are expected to mobilize and manage GCF finance in a country. Their primary roles are to develop and submit funding proposals for projects and programs; oversee project and program management and implementation; deploy a range of financial instruments (grants, concessional loans, equity and guarantees) and mobilize private sector capital. Two institutions in Bangladesh are accredited as NIEs. The NIEs are: Infrastructure Development Company Limited (IDCOL) and Palli Karma-Sahayak Foundation (PKSF).

Native species. Indigenous species of animals or plants that naturally occur in a given region or ecosystem. Under climate change many species colonize new areas where they may become native over time (following IPBES 2019). See also Invasive species

Nature‐based solutions (NbS). Nature-based solutions are actions to protect, sustainably manage and restore natural and modified ecosystems that address societal challenges effectively and adaptively, simultaneously benefiting people and nature.

Natural systems. The dynamic physical, physicochemical and biological components of the Earth system that would operate independently of human activities.

Nature-based solution (NBS). Actions to protect, sustainably manage and restore natural or modified ecosystems that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits. (IUCN, 2016) See also Biodiversity and Ecosystem.

Net zero CO2 emissions. Condition in which anthropogenic carbon dioxide (CO2) emissions are balanced by anthropogenic CO2 removals over a specified period. See also Land use

[Note: Carbon neutrality and net zero CO2 emissions are overlapping concepts. The concepts can be applied at global or sub-global scales (e.g., regional, national and sub-national). At a global scale, the terms carbon neutrality and net zero CO2 emissions are equivalent. At sub-global scales, net zero CO2 emissions is generally applied to emissions and removals under direct control or territorial responsibility of the reporting entity, while carbon neutrality generally includes emissions and removals within and beyond the direct control or territorial responsibility of the reporting entity. Accounting rules specified by GHG programmes or schemes can have a significant influence on the quantification of relevant CO2 emissions and removals.]

New Urban Agenda. The New Urban Agenda was adopted at the United Nations Conference on Housing and Sustainable Urban Development (Habitat III) in Quito, Ecuador, on 20 October 2016. It was endorsed by the United Nations General Assembly at its sixty-eighth plenary meeting of the seventy-first session on 23 December 2016.

Non-climatic driver (non-climate driver). An agent or process outside the climate system that influences a human or natural system.

Non-communicable diseases. Non-communicable diseases (NCDs), also known as chronic diseases, tend to be of long duration and are the result of a combination of genetic, physiological, environmental and behaviors factors. The main types of NCDs are cardiovascular diseases (like heart attacks and stroke), cancers, chronic respiratory diseases (such as chronic obstructive pulmonary disease and asthma) and diabetes (WHO)

Ocean. The interconnected body of saline water that covers 71% of the Earth’s surface, contains 97% of the Earth’s water and provides 99% of the Earth’s biologically-habitable space. It includes the Arctic, Atlantic, Indian, Pacific and Southern Oceans, as well as their marginal seas and coastal waters.

Ocean acidification (OA). A reduction in the pH of the ocean, accompanied by other chemical changes (primarily in the levels of carbonate and bicarbonate ions), over an extended period, typically decades or longer, which is caused primarily by uptake of carbon dioxide (CO2) from the atmosphere, but can also be caused by other chemical additions or subtractions from the ocean. Anthropogenic OA refers to the component of pH reduction that is caused by human activity (IPCC, 2011, p. 37).

Ocean deoxygenation. The loss of oxygen in the ocean. It results from ocean warming, which reduces oxygen solubility and increases oxygen consumption and stratification, thereby reducing the mixing of oxygen into the ocean interior. Deoxygenation can also be exacerbated by the addition of excess nutrients in the coastal zone.

Organizational Learning. The process by which an organization improves itself over time by gaining experience and using it to create knowledge that can be transferred within the organization, beyond the organization, applied again, and improved over time. See also Best Practices.

Oxygen Minimum Zone (OMZ). The midwater layer (200–1000 m) in the open ocean in which oxygen saturation is the lowest in the ocean. The degree of oxygen depletion depends on the largely bacterial consumption of organic matter and the distribution of the OMZs is influenced by large-scale ocean circulation. In coastal oceans, OMZs extend to the shelves and may also affect benthic ecosystems.

Ozone (O3). The triatomic form of oxygen, and a gaseous atmospheric constituent. In the troposphere, O3 is created both naturally and by photochemical reactions involving gases resulting from human activities (e.g., smog).

Tropospheric O3 acts as a greenhouse gas (GHG). In the stratosphere, O3 is created by the interaction between solar ultraviolet radiation and molecular oxygen (O2). Stratospheric O3 plays a dominant role in the stratospheric radiative balance. Its concentration is highest in the ozone layer. See also Short-lived climate forcers (SLCFs). (IPCC 2021).

Ozone. The triatomic form of oxygen (O3), is a gaseous atmospheric constituent. In the troposphere, it is created both naturally and by photo- chemical reactions involving gases resulting from human activities (smog). Tropospheric ozone acts as a greenhouse gas. In the stratosphere, it is created by the interaction between solar ultraviolet radiation and molecular oxygen (O2). Stratospheric ozone plays a dominant role in the stratospheric radiative balance. Its concentration is highest in the ozone layer.

Ozone Layer. The stratosphere contains a layer in which the concentration of ozone is greatest, the so-called ozone layer. The layer extends from about 12 to 40 km above the Earth’s surface. The ozone concentration reaches a maximum between about 20 and 25 km. This layer has been depleted by human emissions of chlorine and bromine compounds. Every year, during the Southern Hemisphere spring, a very strong depletion of the ozone layer takes place over the Antarctic, caused by anthropogenic chlorine and bromine compounds in combination with the specific meteorological conditions of that region. This phenomenon is called the Ozone hole. See also Montreal Protocol.

Paris Agreement. Adopted under the UNFCCC in December 2015 in Paris, France and the agreement came into force on 4 November 2016. One of the goals of the Paris Agreement is ‘Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels. The Paris Agreement has become fully effective in 2020.

Particulate matter (PM). Very small solid particles emitted during the combustion of biomass and fossil fuels. PM may consist of a wide variety of substances. Of greatest concern for health are particulates of diameter less than or equal to 10 nanometers, usually designated as PM10.

Pasture. Area covered with grass or other plants used or suitable for grazing of livestock; grassland.

Path dependence. The generic situation where decisions, events, or outcomes at one point in time constrain adaptation, mitigation, or other actions or options at a later point in time. See also Lock in

Pathways. The temporal evolution of natural and/or human systems towards a future state. Pathway concepts range from sets of quantitative and qualitative scenarios or narratives of potential futures to solution-oriented decision-making processes to achieve desirable societal goals. Pathway approaches typically focus on biophysical, techno-economic, and/or socio-behavioral trajectories and involve various dynamics, goals, and actors across different scales. See also Scenario

Adaptation pathways – A series of adaptation choices involving trade-offs between short-term and long-term goals and values. These are processes of deliberation to identify solutions that are meaningful to people in the context of their daily lives and to avoid potential maladaptation.

Climate-resilient development pathways (CRDPs) – Trajectories that strengthen sustainable development and efforts to eradicate poverty and reduce inequalities while promoting fair and cross-scalar adaptation to and resilience in a changing climate. They raise the ethics, equity, and feasibility aspects of the deep societal transformation needed to drastically reduce emissions to limit global warming (e.g., to well below 2°C) and achieve desirable and livable futures and wellbeing for all.

Climate-resilient pathways – Iterative processes for managing change within complex systems in order to reduce disruptions and enhance opportunities associated with climate change. See also Development pathways and Pathways

Development pathways – Development pathways evolve as the result of the countless decisions being made and actions being taken at all levels of societal structure, as well due to the emergent dynamics within and between institutions, cultural norms, technological systems and other drivers of behavioural change.

Emission pathways – Modelled trajectories of global anthropogenic emissions over the 21st century are termed emission pathways.

Overshoot pathways – Pathways that first exceed a specified concentration, forcing, or global warming level, and then return to or below that level again before the end of a specified period of time (e.g., before 2100). Sometimes the magnitude and likelihood of the overshoot is also characterized. The overshoot duration can vary from one pathway to the next, but in most overshoot pathways in the literature and referred to as overshoot pathways in the AR6, the overshoot occurs over a period of at least one decade and up to several decades.

Representative Concentration Pathways (RCPs) – Scenarios that include time series of emissions and concentrations of the full suite of greenhouse gases (GHGs) and aerosols and chemically active gases, as well as land use/land cover (Moss et al., 2008; van Vuuren et al., 2011),The word representative signifies that each RCP provides only one of many possible scenarios that would lead to the specific radiative forcing characteristics. The term pathway emphasises the fact that not only the long-term concentration levels, but also the trajectory taken over time to reach that outcome are of interest (Moss et al., 2010; van Vuuren et al., 2011).

RCPs usually refer to the portion of the concentration pathway extending up to 2100, for which Integrated assessment models produced corresponding emission scenarios. Extended concentration pathways describe extensions of the RCPs from 2100 to 2300 that were calculated using simple rules generated by stakeholder consultations, and do not represent fully consistent scenarios. Four RCPs produced from Integrated assessment models were selected from the published literature and are used in the Fifth IPCC Assessment and also used in this Assessment for comparison, spanning the range from approximately below 2°C warming to high (>4°C) warming best-estimates by the end of the 21st century: RCP2.6, RCP4.5 and RCP6.0 and RCP8.5.

• RCP2.6: One pathway where radiative forcing peaks at approximately 3 W m-2 and then declines to be limited at 2.6 W m-2 in 2100 (the corresponding Extended Concentration Pathway, or ECP, has constant emissions after 2100).
• RCP4.5 and RCP6.0: Two intermediate stabilisation pathways in which radiative forcing is limited at approximately 4.5 W m-2 and 6.0 W m-2 in 2100 (the corresponding ECPs have constant concentrations after 2150).
• RCP8.5: One high pathway which leads to >8.5 W m-2 in 2100 (the corresponding ECP has constant emissions after 2100 until 2150 and constant concentrations after 2250).

Shared socio-economic pathways (SSPs) –Shared socio-economic pathways (SSPs) have been developed to complement the Representative concentration pathways (RCPs). By design, the RCP emission and concentration pathways were stripped of their association with a certain socio-economic development. Different levels of emissions and climate change along the dimension of the RCPs can hence be explored against the backdrop if different socio-economic development pathways (SSPs) on the other dimension in a matrix. This integrative SSP-RCP framework is now widely used in the climate impact and policy analysis literature (see e.g. http://iconics-ssp.org), where climate projections obtained under the RCP scenarios are analysed against the backdrop of various SSPs.

As several emission updates were due, a new set of emission scenarios was developed in conjunction with the SSPs. Hence, the abbreviation SSP is now used for two things: On the one hand SSP1, SSP2,…, SSP5 is used to denote the five socio-economic scenario families. On the other hand, the abbreviations SSP1-1.9, SSP1-2.6, …, SSP5-8.5 are used to denote the newly developed emission scenarios that are the result of an SSP implementation within an integrated assessment model. Those SSP scenarios are bare of climate policy assumption, but in combination with so-called shared policy assumptions (SPAs), various approximate radiative forcing levels of 1.9, 2.6, …, or 8.5 W m-2 are reached by the end of the century, respectively.

Sustainable development pathways (SDPs) –Trajectories aimed at attaining the Sustainable Development Goals (SDGs) in the short term and the goals of sustainable development in the long term. In the context of climate change, such pathways denote trajectories that address social, environmental, and economic dimensions of sustainable development, adaptation and mitigation, and transformation, in a generic sense or from a particular methodological perspective such as integrated assessment models and scenario simulations.

Precipitation. Water released from clouds in the form of rain, freezing rain, sleet, snow, or hail. It is the primary connection in the water cycle that provides the delivery of atmospheric water to the Earth.

Predictability. The extent to which future states of a system may be predicted based on knowledge of current and past states of the system. Because knowledge of the climate system’s past and current states is generally imperfect, as are the models that utilise this knowledge to produce a climate prediction, and because the climate system is inherently nonlinear and chaotic, predictability of the climate system is inherently limited. Even with arbitrarily accurate models and observations, there may still be limits to the predictability of such a nonlinear system.

Peat. Soft, porous or compressed, sedentary deposit of which a substantial portion is partly decomposed plant material with high water content in the natural state (up to about 90 percent) (IPCC, 2013).

Peatlands. Peatlands are wetland ecosystems where soils are dominated by peat. In peatlands net primary production exceeds organic matter decomposition as a result of waterlogged conditions, which leads to the accumulation of peat.

Pelagic. The pelagic zone consists of the entire water column of the open ocean. It is subdivided into the ‘epipelagic zone’ (<200 m, the uppermost part of the ocean that receives enough sunlight to allow photosynthesis), the ‘mesopelagic zone’ (200–1000 m depth) and the ‘bathypelagic zone’ (>1000 m depth). The term ‘pelagic’ can also refer to organisms that live in the pelagic zone.

Pelagos. Organisms large and small living in the pelagic zones. Includes plankton (small) and nekton (free swimming, large). See Benthos.

Percentiles. A partition value in a population distribution that a given percentage of the data values are below or equal to. The 50th percentile corresponds to the median of the population. Percentiles are often used to estimate the extremes of a distribution. For example, the 90th (10th) percentile may be used to refer to the threshold for the upper (lower) extremes.

Peri-urban areas. Dynamic transition zones that have intense interaction between rural and urban economies, activities, households, and lifestyles. Neither fully rural or urban. (Following Seto, K.C., Sánchez-Rodríguez, R., Fragkias, M. 2010.)

Permafrost. Ground (soil or rock, and included ice and organic material) that remains at or below 0°C for at least two consecutive years (Harris et al., 1988). Note that permafrost is defined via temperature rather than ice content and, in some instances, may be ice-free.

Permafrost degradation. Decrease in the thickness and/or areal extent of permafrost.

Permafrost thaw. Progressive loss of ground ice in permafrost, usually due to input of heat. Thaw can occur over decades to centuries over the entire depth of permafrost ground, with impacts occurring while thaw progresses. During thaw, temperature fluctuations are subdued because energy is transferred by phase change between ice and water. After the transition from permafrost to non-permafrost, ground can be described as thawed.

pH. A dimensionless measure of the acidity of a solution given by its concentration of hydrogen ions (H+). pH is measured on a logarithmic scale where pH = -log10(H+). Thus, a pH decrease of 1 unit corresponds to a 10- fold increase in the concentration of H+, or acidity.

Phenology. The relationship between biological phenomena that recur periodically (e.g., development stages, migration) especially related to climate and seasonal changes.

Photosynthesis. The production of carbohydrates in plants, algae and some bacteria using the energy of light. Carbon dioxide (CO2) is used as the carbon source.

Plankton. Free-floating organisms living in the upper layers of aquatic systems. Their distribution and migration are primarily determined by water currents. A distinction is made between phytoplankton, which depend on photosynthesis for their energy supply, and zooplankton, which feed on phytoplankton, other zooplankton, and bacterioplankton.

Planned relocation (of humans). A form of human mobility response in the face of sea level rise and related impacts. Planned relocation is typically initiated, supervised and implemented from national to local level and involves small communities and individual assets but may also involve large populations. Also termed resettlement, managed retreat, or managed realignment.

Plasticity (biology). Change in organismal trait values in response to an environmental cue, and which does not require change in underlying DNA sequence.

Policies (for climate change mitigation and adaptation). Strategies that enable actions to be undertaken to accelerate adaptation and mitigation. Policies include those developed by national and subnational public agencies, and with the private sector. Policies for adaptation and mitigation often take the form of economic incentives, regulatory instruments, and decision-making and engagement processes.

Political economy. The set of interlinked relationships between people, the state, society and markets as defined by law, politics, economics, customs and power that determine the outcome of trade and transactions and the distribution of wealth in a country or economy.

Potential Evapotranspiration. The potential rate of water loss without any limits imposed by the water supply.

Poverty. A complex concept with several definitions stemming from different schools of thought. It can refer to material circumstances (such as need, pattern of deprivation or limited resources), economic conditions (such as standard of living, inequality or economic position) and/or social relationships (such as social class, dependency, exclusion, lack of basic security or lack of entitlement). See also Poverty trap

Poverty trap. Poverty trap is understood differently across disciplines. In the social sciences, the concept, primarily employed at the individual, household, or community level, describes a situation in which escaping poverty becomes impossible due to unproductive or inflexible resources. A poverty trap can also be seen as a critical minimum asset threshold, below which families are unable to successfully educate their children, build up their productive assets, and get out of poverty. Extreme poverty is itself a poverty trap, since poor persons lack the means to participate meaningfully in society. In economics, the term poverty trap is often used at national scales, referring to a self-perpetuating condition where an economy, caught in a vicious cycle, suffers from persistent underdevelopment (Matsuyama, 2008). Many proposed models of poverty traps are found in the literature.

Pre-industrial (period). The multi-century period prior to the onset of large-scale industrial activity around 1750. The reference period 1850–1900 is used to approximate pre-industrial global mean surface temperature (GMST).

Precursors. Atmospheric compounds that are not greenhouse gases (GHGs) or aerosols, but that have an effect on GHG or aerosol concentrations by taking part in physical or chemical processes regulating their production or destruction rates.

Predictability. The extent to which future states of a system may be predicted based on knowledge of current and past states of the system. Because knowledge of the climate system’s past and current states is generally imperfect, as are the models that utilize this knowledge to produce a climate prediction, and because the climate system is inherently nonlinear and chaotic, predictability of the climate system is inherently limited. Even with arbitrarily accurate models and observations, there may still be limits to the predictability of such a nonlinear system (AMS, 2000).

Primary production. The synthesis of organic compounds by plants and microbes, on land or in the ocean, primarily by photosynthesis using light and carbon dioxide (CO2) as sources of energy and carbon respectively. It can also occur through chemosynthesis, using chemical energy, e.g., in deep sea vents.

Net Primary production (NPP) –The difference between how much CO2 vegetation takes in during photosynthesis (gross primary production) minus how much CO2 the plants release during respiration (IPBES, 2019. Global Assessment).

Projection. A potential future evolution of a quantity or set of quantities, often computed with the aid of a model. Unlike predictions, projections are conditional on assumptions concerning, for example, future socio-economic and technological developments that may or may not be realized. See also Pathways and Scenario

Proxy. A proxy climate indicator is a record that is interpreted, using physical and biophysical principles, to represent some combination of climate-related variations back in time. Climate-related data derived in this way are referred to as proxy data. Examples of proxies include pollen analysis, tree ring records, speleothems, characteristics of corals, and various data derived from marine sediments and ice cores. Proxy data can be calibrated to provide quantitative climate information

Radiative forcing. The change in the net, downward minus upward, radiative flux (expressed in W m-2) at the tropopause or top of atmosphere due to a change in an [external] driver of climate change, such as a change in the concentration of carbon dioxide (CO2), the concentration of volcanic aerosols or in the output of the Sun. The traditional radiative forcing is computed with all tropospheric properties held fixed at their unperturbed values, and after allowing for stratospheric temperatures, if perturbed, to readjust to radiative-dynamical equilibrium. Radiative forcing is called instantaneous if no change in stratospheric temperature is accounted for. The radiative forcing once rapid adjustments are accounted for is termed the effective radiative forcing. Radiative forcing is not to be confused with cloud radiative forcing, which describes an unrelated measure of the impact of clouds on the radiative flux at the top of the atmosphere.

Remote Sensing. Remote sensing is the small- or large-scale acquisition of information of an object or phenomenon by the use of either recording or real-time sensing device(s) that are wireless, or not in physical or intimate contact with the object (such as by way of aircraft, spacecraft, satellite, buoy, or ship). In practice, remote sensing is the stand-off collection through the use of a variety of devices for gathering information on a given object or area.

Representative Concentration Pathways (RCPs). RCP are scenarios that include time series of emissions and concentrations of the full suite of greenhouse gases (GHGs) and aerosols and chemically active gases, as well as land use / land cover. The word ‘representative’ signifies that each RCP provides only one of many possible scenarios that would lead to the specific radiative forcing characteristics. The term ‘pathway’ emphasizes the fact that not only the long-term concentration levels, but also the trajectory taken over time to reach that outcome are of interest (Moss et al., 2010). RCPs were used to develop climate projections in Coupled Model Intercomparison Project CMIP5.

• RCP2.6: One pathway where radiative forcing peaks at approximately 3 W m–2 and then declines to be limited at 2.6 W m–2 in 2100 (the corresponding Extended Concentration Pathway (ECP) assuming constant emissions after 2100).
• RCP4.5 and RCP6.0: Two intermediate stabilization pathways in which radiative forcing is limited at approximately 4.5 W m–2 and 6.0 W m–2 in 2100 (the corresponding ECPs assuming constant concentrations after 2150).
• RCP8.5: One high pathway which leads to >8.5 W m–2 in 2100 (the corresponding ECP assuming constant emissions after 2100 until 2150 and constant concentrations after 2250).

Reasons for Concern (RFCs). Elements of a classification framework, first developed in the IPCC Third Assessment Report, which aims to facilitate judgments about what level of climate change may be dangerous (in the language of Article 2 of the UNFCCC) by aggregating risks from various sectors, considering hazards, exposures, vulnerabilities, capacities to adapt, and the resulting impacts.

Reference period. A time period of interest, or a period over which some relevant statistics are calculated. A reference period can be used as a baseline period or as a comparison to a baseline period.

Reforestation. Conversion to forest of land that has previously contained forests but that has been converted to some other use. See also Afforestation and Forest.

[Note: For a discussion of the term forest and related terms such as afforestation, reforestation and deforestation, see the 2006 IPCC Guidelines for National Greenhouse Gas Inventories and their 2019 Refinement, and information provided by the United Nations Framework Convention on Climate Change (IPCC 2006, 2019; UNFCCC 2021a, 2021b)]

Refugium. A refugium is a geographic area where a population found safety from some threat to its existence. E.g., climate refugia, glacial refugia (refuge from glaciations). See also Climate refugium.

Region. Land and/or ocean area characterized by specific geographical and/or climatological features. The climate of a region emerges from a multi-scale combination of its own features, remote influences from other regions, and global climate conditions.

Regulation. A rule or order issued by governmental executive authorities or regulatory agencies and having the force of law. Regulations implement policies and are mostly specific for particular groups of people, legal entities or targeted activities. Regulation is also the act of designing and imposing rules or orders. Informational, transactional, administrative and political constraints in practice limit the regulator’s capability for implementing preferred policies.

Relative humidity. The relative humidity specifies the ratio of actual water vapour pressure to that at saturation with respect to liquid water or ice at the same temperature.

Reporting. The process of formal reporting of assessment results to the UNFCCC, according to predetermined formats and according to established standards, especially the Intergovernmental Panel on Climate Change (IPCC) Guidelines and GPG (Good Practice Guidance) (UN REDD, 2009).Representative concentration pathways (RCPs). These describe different levels of greenhouse gases and other radiative forcings that might occur in the future. Four pathways span a broad range of forcing in 2100 (2.6, 4.5, 6.0, and 8.5 watts per meter squared) but these do not include any socioeconomic narratives to go alongside them. The RCPs set pathways for greenhouse gas concentrations and, effectively, the amount of warming that could occur by the end of the century. (NAP 2023-2050).

Resilience. The capacity of social, economic, and environmental systems to cope with a hazardous event or trend or disturbance, responding or re-organizing in ways that maintain their essential function, identity, and structure, while also maintaining the capacity for adaptation, learning, and transformation.

Reservoir. A component or components of the climate system where a greenhouse gas (GHG) or a precursor of a greenhouse gas is stored (UNFCCC Article 1.7).

Residual risk. The risk related to climate change impacts that remains following adaptation and mitigation efforts. Adaptation actions can redistribute risk and impacts, with increased risk and impacts in some areas or populations, and decreased risk and impacts in others. See also Loss and Damage

Resilience. The capacity of interconnected social, economic and ecological systems to cope with a hazardous event, trend or disturbance, responding or reorganising in ways that maintain their essential function, identity and structure. Resilience is a positive attribute when it maintains capacity for adaptation, learning and/or transformation (Arctic Council, 2016). See also Hazard, Risk, and Vulnerability.

Resolution. In climate models, this term refers to the physical distance (metres or degrees) between each point on the grid used to compute the equations. Temporal resolution refers to the time step or time elapsed between each model computation of the equations.

Respiration. The process whereby living organisms convert organic matter to carbon dioxide (CO2), releasing energy and consuming molecular oxygen.

Restoration. In environmental context, restoration involves human interventions to assist the recovery of an ecosystem that has been previously degraded, damaged or destroyed.

Return period. An estimate of the average time interval between occurrences of an event (e.g., flood or extreme rainfall) of (or below/above) a defined size or intensity.

Risk. The potential for adverse consequences for human or ecological systems, recognising the diversity of values and objectives associated with such systems. In the context of climate change, risks can arise from potential impacts of climate change as well as human responses to climate change. Relevant adverse consequences include those on lives, livelihoods, health and wellbeing, economic, social and cultural assets and investments, infrastructure, services (including ecosystem services), ecosystems and species.

In the context of climate changeadap impacts, risks result from dynamic interactions between climate-related hazards with the exposure and vulnerability of the affected human or ecological system to the hazards. Hazards, exposure and vulnerability may each be subject to uncertainty in terms of magnitude and likelihood of occurrence, and each may change over time and space due to socio-economic changes and human decision-making.

In the context of climate change responses, risks result from the potential for such responses not achieving the intended objective(s), or from potential trade-offs with, or negative side-effects on, other societal objectives, such as the Sustainable Development Goals (SDGs). Risks can arise for example from uncertainty in implementation, effectiveness or outcomes of climate policy, climate-related investments, technology development or adoption, and system transitions. See also Hazard and Impacts (IPCC 2021).

Risk. Function of hazards, exposure and vulnerability (IPCC AR5). Something creating a hazard that threatens development. In this context, it can be a risk faced in implementing a strategy or a risk arising from the effects of climate change. To safeguard development in areas affected by climate variability and climate change, risks associated with climate hazards must be managed. (GIZ).

Risk assessment. The qualitative and/or quantitative scientific estimation of risks. See also Risk management and Risk perception

Risk Management. The systematic approach and practice of managing uncertainty to minimize potential harm and loss is known as risk management. Risk management comprises risk assessment and analysis, and the implementation of strategies and specific actions to control, reduce and transfer risks. It is widely practiced by organizations to minimize risk in environmental damage, social impacts and damage from fire and natural hazards. Risk management is a core issue for sectors such as water supply, energy and agriculture whose production is directly affected by extremes of weather and climate.

Risk management. Plans, actions, strategies or policies to reduce the likelihood and/or magnitude of adverse potential consequences, based on assessed or perceived risks (IPCC 2021).

Risk perception. The subjective judgment that people make about the characteristics and severity of a risk. See also Risk assessment and Risk management

Risk transfer. The process of formally or informally shifting the financial consequences of particular risks from one party to another whereby a household, community, enterprise, or state authority will obtain resources from the other party after a disaster occurs, in exchange for ongoing or compensatory social or financial benefits provided to that other party.

Runoff. Is the term used to describe the water from rain, snowmelt or irrigation that flows over the land surface and is not absorbed into the ground or evaporated. Instead, it flows into streams or other surface water or land depressions.

Sea ice. Ice found at the sea surface that has originated from the freezing of seawater. Sea ice may be discontinuous pieces (ice floes) moved on the ocean surface by wind and currents (pack ice), or a motionless sheet attached to the coast (land-fast ice). Sea ice concentration is the fraction of the ocean covered by ice. Sea ice less than one year old is called first-year ice. Perennial ice is sea ice that survives at least one summer. It may be subdivided into second-year ice and multi-year ice, where multiyear ice has survived at least two summers.

Sea Level Change. Sea level can change, both globally and locally due to (1) changes in the shape of the ocean basins, (2) a change in ocean volume as a result of a change in the mass of water in the ocean, and (3) changes in ocean volume as a result of changes in ocean water density. Global mean sea level change resulting from change in the mass of the ocean is called barystatic. The amount of barystatic sea level change due to the addition or removal of a mass of water is called its sea level equivalent (SLE). Sea level changes, both globally and locally, resulting from changes in water density are called steric. Density changes induced by tempera- ture changes only are called thermosteric, while density changes induced by salinity changes are called halosteric. Barystatic and steric sea level changes do not include the effect of changes in the shape of ocean basins induced by the change in the ocean mass and its distribution.

Sea level change (sea level rise/sea level fall). Change to the height of sea level, both globally and locally (relative sea level change) [at seasonal, annual, or longer time scales] due to (1) a change in ocean volume as a result of a change in the mass of water in the ocean [(e.g., due to melt of glaciers and ice sheets)], (2) changes in ocean volume as a result of changes in ocean water density [(e.g., expansion under warmer conditions)], (3) changes in the shape of the ocean basins and changes in the Earth’s gravitational and rotational fields, and (4) local subsidence or uplift of the land. Global mean sea level change resulting from change in the mass of the ocean is called barystatic. The amount of barystatic sea level change due to the addition or removal of a mass of water is called its sea level equivalent (SLE). Sea level changes, both globally and locally, resulting from changes in water density are called steric. Density changes induced by temperature changes only are called thermosteric, while density changes induced by salinity changes are called halosteric. Barystatic and steric sea level changes do not include the effect of changes in the shape of ocean basins induced by the change in the ocean mass and its distribution. See also Extreme Sea level (ESL). (IPCC 2021).

Sea surface temperature (SST). The subsurface bulk temperature in the top few meters of the ocean, measured by ships, buoys, and drifters. From ships, measurements of water samples in buckets were mostly switched in the 1940s to samples from engine intake water. Satellite measurements of skin temperature (uppermost layer; a fraction of a millimeter thick) in the infrared or the top centimeter or so in the microwave are also used, but must be adjusted to be compatible with the bulk temperature.

Semi-arid zone. Areas where vegetation growth is constrained by limited water availability, often with short growing seasons and high interannual variation in primary production. Annual precipitation ranges from 300 to 800 mm, depending on the occurrence of summer and winter rains.

Sendai Framework for Disaster Risk Reduction. The Sendai Framework for Disaster Risk Reduction 2015–2030 outlines seven clear targets and four priorities for action to prevent new, and to reduce existing, disaster risks. The voluntary, non-binding agreement recognizes that the State has the primary role to reduce disaster risk but that responsibility should be shared with other stakeholders, including local government and the private sector. Its aim is to achieve ‘substantial reduction of disaster risk and losses in lives, livelihoods and health and in the economic, physical, social, cultural and environmental assets of persons, businesses, communities and countries.’

Sensitivity. Is the degree to which a system is affected, either adversely or beneficially, by climate variability or climate change. The effect may be direct (change in crop yield in response to a change in the mean, range, variability of temperature) or indirect (damages caused by an increase in the frequency of coastal flooding due to sea level rise).

Sensitivity. The degree to which climate variability or change affects a system or species adversely or beneficially. The effect may be direct (e.g., a change in crop yield in response to a change in the mean, range or variability of temperature) or indirect (e.g., damages caused by an increase in the frequency of coastal flooding due to sea-level rise). (NAP 2023-2050)

Sensitivity. The degree to which a system or species is affected, either adversely or beneficially, by climate variability or change. The effect may be direct (e.g., a change in crop yield in response to a change in the mean, range, or variability of temperature) or indirect (e.g., damages caused by an increase in the frequency of coastal flooding due to sea level rise). (IPCC 2021).

Sequestration. The uptake (i.e., the addition of a substance of concern to a reservoir) of carbon containing substances, in particular carbon dioxide in terrestrial or marine reservoirs. Biological sequestration includes direct removal of Co2 from the atmosphere through land use change, afforestation, reforestation, revegetation, carbon storage in landfills and practices that enhance soil carbon in agriculture (cropland management, grazing land management).

Sequestration. The process of storing carbon in a carbon pool. See also Sink. (IPCC 2021).

Settlements. Places of concentrated human habitation. Settlements can range from isolated rural villages to urban regions with significant global influence. They can include formally planned and informal or illegal habitation and related infrastructure. See also Cities, Urban and Urbanization.

Shared Socioeconomic Pathways (SSPs). Over the past few years, an international team of climate scientists, economists and energy systems modelers have built a range of new pathways that examine how global society, demographics and economics might change over the next century. They are collectively known as the SSPs. The SSPs set the stage on which reductions in emissions will or will not be achieved. They are based on five narratives describing broad socioeconomic trends that could shape future society. These are intended to span the range of plausible futures. They include: a world of sustainability- focused growth and equality (SSP1); a ‘middle of the road’ world where trends broadly follow their historical patterns (SSP2); a fragmented world of ‘resurgent nationalism’ (SSP3); a world of ever-increasing inequality (SSP4); and a world of rapid and unconstrained growth in economic output and energy use (SSP5).

Shelf seas. Relatively shallow water covering the shelf of continents or around islands. The limit of shelf seas is conventionally considered as 200 m water depth at the continental shelf edge, where there is usually a steep slope to the deep ocean floor. During glacial periods, most shelf seas are lost since they become land as the build-up of ice sheets caused a decrease of global sea level.

Sink. Any process, activity or mechanism which removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere (UNFCCC Article 1.8 (UNFCCC, 1992)). See also Sequestration

Small island developing states (SIDS). Small island developing states (SIDS), as recognized by the United Nations OHRLLS (Office of the High Representative for the Least Developed Countries, Landlocked Developing Countries and Small Island Developing States), are a distinct group of developing countries facing specific social, economic and environmental vulnerabilities (UN-OHRLLS, 2011). They were recognized as a special case both for their environment and development at the Rio Earth Summit in Brazil in 1992. Fifty-eight countries and territories are presently classified as SIDS by the UN OHRLLS, with 38 being UN member states and 20 being Non- UN Members or Associate Members of the Regional Commissions (UN-OHRLLS, 2018).

Snow cover extent. The areal extent of snow-covered ground.

Snow water equivalent (SWE). The depth of liquid water that would result if a mass of snow melted completely.

Soft adaptation limit. Options may exist but are currently not available to avoid intolerable risks through adaptive action. But such limits can be overcome by addressing a range of constraints such as financial, governance, institutional and policy constraints.

Social inclusion. A process of improving the terms of participation in society, particularly for people who are disadvantaged, through enhancing opportunities, access to resources, and respect for rights (UN, DESA 2016).

Social infrastructure. See infrastructure

Social justice. See Justice

Social learning. A process of social interaction through which people learn new behaviors, capacities, values, and attitudes.

Social protection. In the context of development aid and climate policy, social protection usually describes public and private initiatives that provide income or consumption transfers to the poor, protect the vulnerable against livelihood risks, and enhance the social status and rights of the marginalized, with the overall objective of reducing the economic and social vulnerability of poor, vulnerable, and marginalized groups (Devereux and Sabates- Wheeler, 2004). In other contexts, social protection may be used synonymously with social policy and can be described as all public and private initiatives that provide access to services, such as health, education, or housing, or income and consumption transfers to people. Social protection policies protect the poor and vulnerable against livelihood risks and enhance the social status and rights of the marginalized, as well as prevent vulnerable people from falling into poverty.

Social-ecological system. An integrated system that includes human societies and ecosystems, in which humans are part of nature. The functions of such a system arise from the interactions and interdependence of the social and ecological subsystems. The system’s structure is characterized by reciprocal feedbacks, emphasizing that humans must be seen as a part of, not apart from, nature (Arctic Council, 2016; Berkes and Folke, 1998).

Soil erosion. The displacement of the soil by the action of water or wind. Soil erosion is a major process of land degradation.

Soil moisture. Water stored in the soil in liquid or frozen form. Root-zone soil moisture is of most relevance for plant activity.

Soil organic carbon. Carbon contained in soil organic matter.

Soil organic matter. The organic component of soil, comprising plant and animal residue at various stages of decomposition, and soil organisms.

Solar Radiation Modification (SRM). Refers to a range of radiation modification measures not related to greenhouse gas (GHG) mitigation that seek to limit global warming. Most methods involve reducing the amount of incoming solar radiation reaching the surface, but others also act on the longwave radiation budget by reducing optical thickness and cloud lifetime.

Solution space. The set of biophysical, cultural, socio-economic, and political-institutional dimensions within which opportunities and constraints determine why, how, when, and who acts to reduce climate risks. Within these dimensions, there are ‘hard’ (unsurpassable) limits and ‘soft’ (surpass able) limits. The boundaries of the solution space are path dependent, contested, and in constant flux (Haasnoot et. al. 2020).

Source. Any process or activity which releases a greenhouse gas, an aerosol or a precursor of a greenhouse gas into the atmosphere (UNFCCC Article 1.9). See also Sink and Sequestration

Southern Ocean. The ocean region encircling Antarctica that connects the Atlantic, Indian and Pacific Oceans together, allowing inter-ocean exchange. This region is the main source of much of the deep water of the world’s ocean and also provides the primary return pathway for this deep water to the surface (Marshall and Speer, 2012; Toggweiler and Samuels, 1995). The drawing up of deep waters and the subsequent transport into the ocean interior has major consequences for the global heat, nutrient, and carbon balances, as well as the Antarctic cryosphere and marine ecosystems.

Spatial and temporal scales. Climate may vary on a large range of spatial and temporal scales. Spatial scales may range from local (less than 100 000 km2), through regional (100 000 to 10 million km2) to continental (10 to 100 million km2).Temporal scales may range from seasonal to geological (up to hundreds of millions of years).

Standards. Set of rules or codes mandating or defining product performance (e.g., grades, dimensions, characteristics, test methods, and rules for use). Product, technology or performance standards establish minimum requirements for affected products or technologies. Standards impose reductions in greenhouse gas (GHG) emissions associated with the manufacture or use of the products and/or application of the technology.

Storm surge. The temporary increase, at a particular locality, of the height of the sea due to extreme meteorological conditions. The storm surge is defined as being the excess above the level expected from the tidal variation alone at that time and place.

Storm surge. The temporary increase, at a particular locality, in the height of the sea due to extreme meteorological conditions (low atmospheric pressure and/or strong winds). The storm surge is defined as being the excess above the level expected from the tidal variation alone at that time and place. See also Extreme Sea level and Seal level change (sea level rise/ sea level fall). (IPCC 2021).

Storms Scenario. A plausible description of how the future may develop based on a coherent and internally consistent set of assumptions about key driving forces (e.g., rate of technological change (TC), prices) and relationships. Note that scenarios are neither predictions nor forecasts, but are used to provide a view of the implications of developments and actions. See also Pathways

Concentration scenario –A plausible representation of the future development of atmospheric concentrations of substances that are radiatively active (e.g., greenhouse gases (GHGs), aerosols, tropospheric ozone), plus human- induced land cover changes that can be radiatively active via albedo changes, and often used as input to a climate model to compute climate projections.

Emission scenario –A plausible representation of the future development of emissions of substances that are radiatively active (e.g., greenhouse gases (GHGs), or aerosols) based on a coherent and internally consistent set of assumptions about driving forces (such as demographic and socio-economic development, technological change, energy and land use) and their key relationships. Concentration scenarios, derived from emission scenarios, are often used as input to a climate model to compute climate projections.

Reference scenario –The scenario used as starting or reference point for a comparison between two or more scenarios.

[Note 1: In many types of climate change research, reference scenarios reflect specific assumptions about patterns of socio-economic development and may represent futures that assume no climate policies or specified climate policies, for example those in place or planned at the time a study is carried out. Reference scenarios may also represent futures with limited or no climate impacts or adaptation, to serve as a point of comparison for futures with impacts and adaptation. These are also referred to as baseline scenarios in the literature.

Note 2: Reference scenarios can also be climate policy or impact scenarios, which in that case are taken as a point of comparison to explore the implications of other features, e.g., of delay, technological options, policy design and strategy or to explore the effects of additional impacts and adaptation beyond those represented in the reference scenario.

Note 3: The term business as usual scenario has been used to describe a scenario that assumes no additional policies beyond those currently in place and that patterns of socio-economic development are consistent with recent trends. The term is now used less frequently than in the past.

Note 4: In climate change attribution or impact attribution research reference scenarios may refer to counterfactual historical scenarios assuming no anthropogenic greenhouse gas emissions (climate change attribution) or no climate change (impact attribution)]

Socio-economic scenario –A scenario that describes a possible future in terms of population, gross domestic product (GDP), and other socio-economic factors relevant to understanding the implications of climate change.

Storyline. A way of making sense of a situation or a series of events through the construction of a set of explanatory elements. Usually it is built on logical or causal reasoning. In climate research, the term storyline is used both in connection to scenarios as related to a future trajectory of the climate and human systems or to a weather or climate event. In this context, storylines can be used to describe plural, conditional possible futures or explanations of a current situation, in contrast to single, definitive futures or explanations.

Stranded assets. Assets exposed to devaluations or conversion to ‘liabilities’ because of unanticipated changes in their initially expected revenues due to innovations and/or evolutions of the business context, including changes in public regulations at the domestic and international levels.

Stratification. Process of forming of layers of (ocean) water with different properties such as salinity, density and temperature that act as barrier for water mixing. The strengthening of near-surface stratification generally results in warmer surface waters, decreased oxygen levels in deeper water, and intensification of ocean acidification (OA) in the upper ocean.

Streamflow. Water flow within a river channel, for example, expressed in m3 s-1. A synonym for river discharge.

Stressors. Events and trends, often not climate-related, that have an important effect on the system exposed and can increase vulnerability to climate-related risk.

Sustainability. Involves ensuring the persistence of natural and human systems, implying the continuous functioning of ecosystems, the conservation of high biodiversity, the recycling of natural resources and, in the human sector, successful application of justice and equity.

Sustainable development (SD). Development that meets the needs of the present without compromising the ability of future generations to meet their own needs (WCED, 1987) and balances social, economic and environmental concerns. See also Development pathways and Sustainable Development Goals (SDGs)

Sustainable Development Goals (SDGs). The 17 global goals for development for all countries established by the United Nations through a participatory process and elaborated in the 2030 Agenda for Sustainable Development, including ending poverty and hunger; ensuring health and wellbeing, education, gender equality, clean water and energy, and decent work; building and ensuring resilient and sustainable infrastructure, cities and consumption; reducing inequalities; protecting land and water ecosystems; promoting peace, justice and partnerships; and taking urgent action on climate change. See also Development pathways and Sustainable Development

Sustainable Development Goal (SDG) No. 13: Climate action. Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters in all countries.

• Integrate climate change measures into national policies, strategies and planning.
• Improve education, awareness-raising and human and institutional capacity on climate change mitigation, adaptation, impact reduction and early warning.
• Implement the commitment undertaken by developed-country parties to the United Nations Framework Convention on Climate Change to a goal of mobilizing jointly $100 billion annually by 2020 from all sources to address the needs of developing countries in the context of meaningful mitigation actions and transparency on implementation and fully operationalize the Green Climate Fund through its capitalization as soon as possible.
• Promote mechanisms for raising capacity for effective climate change-related planning and management in least developed countries and small island developing States, including focusing on women, youth and local and marginalized communities.

Sustainable forest management. The stewardship and use of forests and forest lands in a way, and at a rate, that maintains their biodiversity, productivity, regeneration capacity, vitality and their potential to fulfil, now and in the future, relevant ecological, economic and social functions, at local, national, and global levels, and that does not cause damage to other ecosystems (Forest Europe, 1993).

Sustainable land management. The stewardship and use of land resources, including soils, water, animals and plants, to meet changing human needs, while simultaneously ensuring the long-term productive potential of these resources and the maintenance of their environmental functions (Adapted from WOCAT, undated).

Sympagic. Organisms and habitats related to the sea ice, analogous to ‘pelagic’ (> water-column’) or ‘benthic’ (> ‘sea- floor’).

Structural Means. Any physical construction to reduce or avoid possible impacts of hazards or application of engineering techniques to achieve hazard resistance and resilience in structures or systems is known as structural means.

Surface urban heat island intensity (SUHII). The difference in temperature between the urban and surrounding rural areas is possibly the most visible effect associated with the urbanization process and is mainly due to increased human activities. This observed temperature gradient is typically known as the urban heat island (UHI). Two major types of UHIs are the atmospheric urban heat island (AUHI), and the surface urban heat island (SUHI).

Sustainable livelihood. Livelihood that endures over time and is resilient to the impacts of various types of shocks including climate and economic.

System of interest. The ‘system of interest’ is the unit or space chosen to assess concerning climate change impacts. Depending on the objective of the analysis, the system of interest may be determined at different levels, e.g., a single crop system, an ecosystem or a region.

Teleconnection. Association between climate variables at widely separated, geographically fixed locations related to each other through physical processes and oceanic and/or atmospheric dynamical pathways. Teleconnections can be caused by several climate phenomena, such as Rossby wave-trains, mid-latitude jet and storm track displacements, fluctuations of the Atlantic Meridional Overturning Circulation, fluctuations of the Walker circulation, etc. They can be initiated by modes of climate variability thus providing the development of remote climate anomalies at various temporal lags.

Temperature. Is the expected temperature in degrees, valid for the indicated hour. Global temperature is an average of air temperature recordings from weather stations on land and sea as well as some satellite measurements. Extreme temperature events (i.e., maximum, minimum) may have short-term durations of a few days with temperature increases of over 5C above normal temperatures.

Temperature overshoot. Exceedance of a specified global warming level, followed by a decline to or below that level during a specified period of time (e.g., before 2100). Sometimes the magnitude and likelihood of the overshoot is also characterized. The overshoot duration can vary from one pathway to the next but in most overshoot pathways in the literature and referred to as overshoot pathways in the AR6, the overshoot occurs over a period of at least one and up to several decades. See also Pathways.

Tier. In the context of the IPCC Guidelines for National Greenhouse Gas Inventories, a tier represents a level of methodological complexity. Usually, three tiers are provided. Tier 1 is the basic method, Tier 2 intermediate and Tier 3 most demanding in terms of complexity and data requirements. Tiers 2 and 3 are sometimes referred to as higher tier methods and are generally considered to be more accurate (IPCC, 2019).

Tipping element. A component of the Earth system that is susceptible to a tipping point. See also Abrupt climate change and Tipping point.

Tipping point. A critical threshold beyond which a system reorganizes, often abruptly and/or irreversibly. See also abrupt climate change

Trade-off. A competition between different objectives within a decision situation, where pursuing one objective will diminish achievement of other objective(s). A trade-off exists when a policy or measure aimed at one objective (e.g., reducing GHG emissions) reduces outcomes for other objective(s) (e.g., biodiversity conservation, energy security) due to adverse side effects, thereby potentially reducing the net benefit to society or the environment. See also Adverse side-effect, Co-benefit

Transformation. A change in the fundamental attributes of natural and human systems.

Transformation. A change in the fundamental attributes of a system, often based on altered paradigms, goals or values due to climate change impacts. Transformations can occur in technological or biological systems, financial structures, and regulatory, legislative or administrative regimes.

Deliberate Transformations – A profound shift towards sustainability, envisioned and intended by at least some societal actors, facilitated by changes in individual and collective values and behaviors, and a fairer balance of political, cultural, and institutional power in society.

Societal (social) Transformations – A change in the fundamental attributes of human systems advanced by societal actors(IPCC 2021).

Transformative adaptation. Transformative adaptation is a strategy that aims to reduce the root causes of vulnerability to climate change in the long- term by shifting systems away from unsustainable or undesirable trajectories. Systems become more adaptive to climate change by transforming their primary characteristics through transformative adaptation.

Transformative capacity‐building. Transformative capacity is the capacity of an individual, an organization or a system to be able to both transform themselves and their society in a deliberate, conscious way. This involves the ability to transform the fundamental and core attributes of a system to tackle the adverse effects of climate change.

Transformation change. The complex challenges of climate change demand sometimes uncompromising action to affect large scale change across the globe. Transformational change is generally understood as a fundamental change at a systematic level, across complex, dynamic challenges that have a web of interconnected elements. The scale of ambition distinguishes transformational change from incremental adaptation processes.

Transformative change. A system-wide change that requires more than technological change through consideration of social and economic factors that, with technology, can bring about rapid change at scale.

Transition. The process of changing from one state or condition to another in a given period of time. Transition can occur in individuals, firms, cities, regions and nations, and can be based on incremental or transformative change.

Threshold. The level of magnitude of a system process at which sudden or rapid change occurs. A point or level at which new properties emerge in an ecological, economic, or other system, invalidating predictions based on mathematical relationships that apply at lower levels.

Just transitions. A set of principles, processes and practices that aim to ensure that no people, workers, places, sectors, countries, or regions are left behind in the transition from a high-carbon to a low-carbon economy. It stresses the need for targeted and proactive measures from governments, agencies, and authorities to ensure that any negative social, environmental, or economic impacts of economy-wide transitions are minimized, whilst benefits are maximized for those disproportionally affected. Key principles of just transitions include: respect and dignity for vulnerable groups; fairness in energy access and use, social dialogue and democratic consultation with relevant stakeholders; the creation of decent jobs; social protection; and rights at work. Just transitions could include fairness in energy, land use and climate planning and decision-making processes; economic diversification based on low-carbon investments; realistic training/retraining programs that lead to decent work; gender specific policies that promote equitable outcomes; the fostering of international cooperation and coordinated multilateral actions; and the eradication of poverty. Lastly, just transitions may embody the redressing of past harms and perceived injustices. (ILO 2015; UNFCCC 2016)

Tree line. The upper limit of tree growth in mountains or at high latitudes. It is more elevated or more poleward than the forest line.

Tropical cyclone. The general term for a strong, cyclonic-scale disturbance that originates over tropical oceans. Distinguished from weaker systems (often named tropical disturbances or depressions) by exceeding a threshold wind speed. A tropical storm is a tropical cyclone with one-minute average surface winds between 18 and 32 m s-

1. Beyond 32 m s-1, a tropical cyclone is called a hurricane, typhoon, or cyclone, depending on geographic location.

Tsunami. A wave, or train of waves, produced by a disturbance such as a submarine earthquake displacing the sea floor, a landslide, a volcanic eruption, or an asteroid impact.

Tundra. A treeless biome characteristic of polar and alpine regions.

Uncertainty. An expression of the degree to which the exact value of a parameter is unknown. Uncertainty can result from lack of information or from disagreement about what is known or even knowable. Uncertainty can be represented by quantitative measures or by qualitative statements (oral history, experts).

Uncertainty. A state of incomplete knowledge that can result from a lack of information or from disagreement about what is known or even knowable. It may have many types of sources, from imprecision in the data to ambiguously defined concepts or terminology, incomplete understanding of critical processes, or uncertain projections of human behaviour. Uncertainty can therefore be represented by quantitative measures (e.g., a probability density function) or by qualitative statements (e.g., reflecting the judgment of a team of experts) (see Moss and Schneider, 2000; IPCC, 2004; Mastrandrea et al., 2010). See also Agreement, Confidence, and Likelihood

Deep uncertainty – A situation of deep uncertainty exists when experts or stakeholders do not know or cannot agree on:

(1) the probability distributions used to represent uncertainty about key variables and parameters; and/or

(2) how to weigh and value desirable alternative outcomes (Lempert et al., 2003). (IPCC 2021).

United Nations Framework Convention on Climate Change (UNFCCC). The UNFCCC was adopted in May 1992 and opened for signature at the 1992 Earth Summit in Rio de Janeiro. It entered into force in March 1994 and as of May 2018 had 197 Parties (196 States and the European Union). The Convention’s ultimate objective is the ‘stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system’. The provisions of the Convention are pursued and implemented by two treaties: the Kyoto Protocol and the Paris Agreement.

Uptake. The transfer of substances (such as carbon) or energy (e.g., heat) from one compartment of a system to another; for example, in the Earth system from the atmosphere to the ocean or to the land. See also Sequestration, Sink and Source

Upwelling region. A region of an ocean were cold, typically nutrient-rich waters well up from the deep ocean.

Urban. The categorization of areas as “urban” by government statistical departments is generally based either on population size, population density, economic base, provision of services, or some combination of the above. Urban systems are networks and nodes of intensive interaction and exchange including capital, culture, and material objects. Urban areas exist on a continuum with rural areas and tend to exhibit higher levels of complexity, higher populations and population density, intensity of capital investment, and a preponderance of secondary (processing) and tertiary (service) sector industries. The extent and intensity of these features varies significantly within and between urban areas. Urban places and systems are open with much movement and exchange between more rural areas as well as other urban regions. Urban areas can be globally interconnected facilitating rapid flows between them – of capital investment, of ideas and culture, human migration, and disease. See also city, city region urbanization, urban systems,

Urban and Peri-urban agriculture. The cultivation of crops and rearing of animals for food and other uses within and surrounding the boundaries of cities, including fisheries and forestry (EPRS, 2014).

Urban heat island (UHI). The relative warmth of a city compared with surrounding rural areas, associated with heat trapping due to land use, the configuration and design of the built environment, including street layout and building size, the heat-absorbing properties of urban building materials, reduced ventilation, reduced greenery and water features, and domestic and industrial heat emissions generated directly from human activities.

Urbanization. Urbanization is a multi-dimensional process that involves at least three simultaneous changes: 1) land use change: transformation of formerly rural settlements or natural land into urban settlements; 2) demographic change: a shift in the spatial distribution of a population from rural to urban areas; and 3) infrastructure change: an increase in provision of infrastructure services including electricity, sanitation, etc. Urbanization often includes changes in lifestyle, culture, and behavior, and thus alters the demographic, economic, and social structure of both urban and rural areas. (Based on World Urbanization Prospects 2018; IPCC 2014; Stokes and Seto, 2019) See also Settlements, Urban, Urban areas and Urban Systems.

Urban Systems. Urban systems refer to two interconnected systems– first, the comprehensive collections of city elements with multiple dimensions and characteristics: a) encompass physical, built, socio-economic-technical, political, and ecological subsystems; b) integrate social agent/constituency/processes with physical structure and processes; and c) exist within broader spatial and temporal scales and governance and institutional contexts; and second, the global system of cities and towns. See also City region, Urban and Urban areas.

Values and Beliefs. Fundamental attitudes about what is important, good, and right; strongly held principles or qualities intrinsically valuable or desirable, often enshrined in laws, traditions, and religions. Examples include human rights, subsistence, and equitable distribution of costs and benefits of climate policies (Hulme, 2009, 2018; Nakashima et al., 2012; UNFCCC, 1992; UN Universal Declaration of Human Rights, 1948).

Vector-borne disease. Illnesses caused by parasites, viruses and bacteria that are transmitted by various vectors (e.g. mosquitoes, sandflies, triatomine bugs, blackflies, ticks, tsetse flies, mites, snails and lice) (UNEP 2018).

Ventilation (ocean). The exchange of ocean properties with the atmospheric surface layer such that property concentrations are brought closer to equilibrium values with the atmosphere (AMS, 2000), and the processes that propagate these properties into the ocean interior.

Vulnerability. Refers to the possibility to be affected by an event, coupled with a ;ack of resources or capacities to cope (lack of anticipation, reactivity or recovery). More precisely, the concept of vulnerability refers to all development factors that contribute to increasing (=sensitivity) or reducing (=capacity) risks (IPCC AR5 2019). Refers to the degree to which a system is susceptible to, and unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude, and rate of climate change and variation to which a system is exposed, its sensitivity, and its adaptive capacity (IPCC, AR4, 2007).

Vulnerability. The propensity or predisposition to be adversely affected. Vulnerability encompasses a variety of concepts and elements including sensitivity or susceptibility to harm and lack of capacity to cope and adapt. See also Exposure, Hazard and Risk(IPCC 2021).

Vulnerability assessment. The vulnerability assessment attempts to identify the root cause for a systems’ vulnerability to climate change. It helps to understand and identify the vulnerabilities of a construction or a community to climate change and other hazards and take appropriate measures to minimize their potential impact.

Vulnerability index. A metric characterizing the vulnerability of a system. A climate vulnerability index is typically derived by combining, with or without weighting, several indicators assumed to represent vulnerability.

Vulnerable Communities. People with special needs include members of the community with little or no ability to successfully address, implement or be fully responsible for their own emergency preparedness, response or recovery is known as vulnerable communities. This includes people whose life circumstances leave them unable or unwilling to follow emergency instruction as well as anyone unable or unwilling to fully access or use preparedness and responsive services.

Water. Is a chemical substance with the chemical formula H2O. Its molecule contains oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state (water vapor).

Water-borne disease. Illnesses that transmitted through contact with or consumption of unsafe or contaminated water (UNEP 2018).

Water security. The capacity of a population to safeguard sustainable access to adequate quantities of acceptable quality water for sustaining livelihoods, human well-being, and socio-economic development, for ensuring protection against water-borne pollution and water-related disasters, and for preserving ecosystems in a climate of peace and political stability (UN-Water, 2013).

Water-use efficiency. Carbon gain by photosynthesis per unit of water lost by evapotranspiration. It can be expressed on a short- term basis as the ratio of photosynthetic carbon gain per unit transpiration water loss, or on a seasonal basis as the ratio of net primary production or agricultural yield to the amount of water used.

Weather. The behavior of the atmosphere on a day-to-day basis in a relatively local area is known as weather. A description of the weather would include daily temperatures, relative humidity, sunshine, wind and rainfall.

Weathering. The gradual removal of atmospheric CO2 through dissolution of silicate and carbonate rocks. Weathering may involve physical processes (mechanical weathering) or chemical activity (chemical weathering).

Well-being. A state of existence that fulfils various human needs, including material living conditions and quality of life, as well as the ability to pursue one’s goals, to thrive, and feel satisfied with one’s life. Ecosystem well-being refers to the ability of ecosystems to maintain their diversity and quality.

Wetland. Land that is covered or saturated by water for all or part of the year (e.g., peatland).