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The physiological adaptation to climatic variations.



See Adaptive capacity.



Adjustment in natural or human systems to a new or changing environment.  Adaptation to climate change refers to adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities. Various types of adaptation can be distinguished, including anticipatory and reactive adaptation, private and public adaptation, and autonomous and planned adaptation.


Adaptation Assessment

The practice of identifying options to adapt to climate change and evaluating them in terms of criteria such as availability, benefits, costs, effectiveness, efficiency, and feasibility.


Adaptation Benefits

The avoided damage costs or the accrued benefits following the adoption and implementation of adaptation measures.


Adaptation Costs

Costs of planning, preparing for, facilitating, and implementing adaptation measures,

including transition costs.


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.



Reduction in emissions by sources or enhancement of removals by sinks that is additional to any that would occur in the absence of a Joint Implementation or a Clean Development Mechanism project activity as defined in the Kyoto Protocol Articles on Joint Implementation and the Clean Development Mechanism. This definition may be further broadened to include financial, investment, and technology additionality. Under

“financial additionality,” the project activity funding shall be additional to existing

Global Environmental Facility, other financial commitments of Parties included in Annex I, Official Development Assistance, and other systems of cooperation. Under “investment additionality,” the value of the Emissions Reduction Unit/Certified Emission Reduction Unit shall significantly improve the financial and/or commercial viability of the project activity. Under “technology additionality,” the technology used for the project activity shall be the best available for the circumstances of the host Party.


Adjustment time

See response time.



A collection of airborne solid or liquid particles, with a typical size between 0.01 and 10mm that reside in the atmosphere for at least several hours. Aerosols may be of either natural or anthropogenic origin. Aerosols may influence climate in two ways: directly through scattering and absorbing radiation, and indirectly through acting as condensation nuclei for cloud dormation or modifying the optical properties and lifetime of clouds. See indirect aerosol effect.



Planting of new forests on lands that historically have not contained forests.


Algal Blooms

A reproductive explosion of algae in a lake, river, or ocean.



The biogeographic zone made up of slopes above timberline and characterized by the presence of rosette-forming herbaceous plants and low shrubby slow-growing woody plants.


Alternative Energy

Energy derived from non-fossil-fuel sources.


Ancillary Benefits

Complementary benefits of a climate policy including improvements in local air quality and reduced reliance of imported fossil fuels.



Resulting from or produced by human beings.


Anthropogenic Emissions

Emissions of greenhouse gases, greenhouse gas precursors, and aerosols associated with human activities. These include burning of fossil fuels for energy, deforestation, and land-use changes that result in net increase in emissions.



Under an emissions trading scheme, permits to emit can initially either be given away for free, usually under a ‘grandfathering’ approach based on past emissions in a base year or an ‘updating’ approach based on the more recent emissions. The alternative is to auction permits in an initial market offering.



A stratum of permeable rock that bears water. An unconfined aquifer is recharged directly by local rainfall, rivers, and lakes, and the rate of recharge will be influenced by the permeability of the overlying rocks and soils. A confined aquifer is characterized by an overlying bed that is impermeable andthe local rainfall does not influence the aquifer.


Arid Regions

Ecosystems with less than 250 mm precipitation per year.



The gaseous envelop surrounding the Earth. The dry atmosphere consists almost entirely of nitrogen (78.1% volume mixingratio) and oxygen (20.9% volume mixing ratio), together with a number of trace gases, such as argon (0.93% volume mixing ratio), helium, and radiatively active greenhouse gases such as carbon dioxide (0.035% volume mixing ratio) and ozone. In addition, the atmosphere contains water vapor, whose amount is highly variable but typically 1% volume mixing ratio. The atmosphere also contains clouds and aerosols.

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