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 (MA, 2005).

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.

Climate Change Adaptation - The process of adjustment to actual or expected climate and its effects. In human systems, adaptation seeks to moderate or avoid harm or exploit beneficial opportunities. In some natural systems, human intervention may facilitate adjustment to expected climate and its effects.

Climate projection - A climate projection is the simulated response of the climate system to a scenario of future emission or concentration of greenhouse gases and aerosols, generally derived using climate models.

Coupled Model Intercomparison Project (CMIP) – A climate modelling activity from the World Climate Research Programme (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).

Disaster - A serious disruption of the functioning of a community or a society involving widespread human, material, economic or environmental losses and impacts, which exceeds the ability of the affected community or society to cope using its own resources.

Disaster Risk Reduction - 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.

Exposure - The 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.

Hazards - 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.

Likelihood of Occurrence of Hazard - pertains to the probability of occurrence of a certain hazard based on its historical or projected occurrence. It may also pertains to hazard recurrence or return period based on local historical disaster (Section 1.3) or perceived recurrence of hazards based on scientific findings. 

Temporal Probability - the probability of a specific hazard scenario occurring within a given return period in a particular area.

Locational/Spatial Probability - the probability of a specific hazard scenario occurring within a given return period in a particular area, affecting the elements at risk.

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).

Impact - The consequences of realized 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 to effects on lives, livelihoods, health and well–being, 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.

Risk - The potential for adverse consequences for human or ecological systems, recognizing 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 well–being, economic, social and cultural assets and investments, infrastructure, services (including ecosystem services), ecosystems and species.

In the context of climate change 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 the implementation, effectiveness or outcomes of climate policy, climate–related investments, technology development or adoption, and system transitions. See also Hazard and Impacts.

Risk Framework - The IPCC Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) and WG II of the Fifth Assessment Report (AR5) introduced an explicit risk framework where risk is conceptualized as a function of the interaction between climate hazards, vulnerability, and exposure. Since the Sixth Assessment Report (AR6), the framework has placed greater emphasis on the role of responses to climate change in shaping risk determinants, particularly in heritage management and climate change adaptation. Additionally, the petal model now acknowledges multiple determinants of risk—including hazards, vulnerabilities, exposures, and responses to better capture how responses influence each risk component and to reflect the multidimensionality and complexity of climate change risk (Ara Begum et al., 2022).

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.