B Glossary of Terms 982 Glossary of Terms Ablation Adaptive Capacity All processes by which snow and ice are lost from a glacier, The ability of a system to adjust to climate change (i n c l u d i n g floating ice, or snow cover. climate variability and extremes) to moderate potential d a mages, to take advantage of opportunities, or to cope with Acclimatization the consequences. The physiological adaptation to climatic variations. Aero-Allergens Active Layer Allergens present in the air. The top layer of soil in permafrost that is subjected to seasonal freezing and thawing. Aerosols Acollection of airborne solid or liquid particles, with a typical Adaptability size between 0.01 and 10 mm that reside in the atmosphere See adaptive capacity. for at least several hours. Aerosols may be of either natural or anthropogenic origin. Aerosols may influence climate in Adaptation two ways: directly through scattering and absorbing radiation, Adjustment in natural or human systems in response to actual and indirectly through acting as condensation nuclei for or expected climatic st i m u l i or their effects, which moderates cloud formation or modifying the optical properties and harm or exploits beneficial opportunities. Various types of l i f etime of clouds. adaptation can be distinguished, including anticipatory and reactive adaptation, private and public adaptation, and Afforestation autonomous and planned adaptation: Planting of new forests on lands that historically have not – Anticipatory Adaptation—Adaptation that takes contained forests. For a discussion of the term forest and place before impacts of climate change are observed. related terms such as afforestation, reforestation, and Also referred to as proactive adaptation. deforestation, see the IPCC Special Report on Land Use, – Autonomous Adaptation—Adaptation that does not Land-Use Change, and Forestry (IPCC, 2000). constitute a conscious response to climatic stimuli but is triggered by ecological changes in natural Aggregate Impacts s y stems and by market or welfare changes in human Total impacts summed up across sectors and/or regions. The systems. Also referred to as spontaneous adaptation. aggregation of impacts requires knowledge of (or assumptions – Planned Adaptation—Adaptation that is the result of about) the relative importance of impacts in different sectors a deliberate policy decision, based on an awareness and regions. Measures of aggregate impacts include, for that conditions have changed or are about to change example, the total number of people affected, change in net and that action is required to return to, maintain, or primary productivity, number of systems undergoing change, achieve a desired state. or total economic costs. – Private Adaptation—Adaptation that is initiated and implemented by individuals, households or private Agronomy companies. Private adaptation is usually in the The branch of agriculture that deals with the theory and actor’s rational self-interest. practice of field-crop production and the scientific – Public Adaptation—Adaptation that is initiated and management of soil. implemented by governments at all levels. Public adaptation is usually directed at collective needs. Alases – Reactive Adaptation—Adaptation that takes place Coalescing thaw depressions. after impacts of climate change have been observed. See also adaptation assessment, adaptation benefits, Albedo adaptation costs, adaptive capacity, and maladaptation. The fraction of solar radiation reflected by a surface or object, often expressed as a percentage. Snow-covered Adaptation Assessment s u rfaces have a high albedo; the albedo of soils ranges from The practice of identifying options to adapt to climate change high to low; vegetation-covered surfaces and oceans have a and evaluating them in terms of criteria such as availability, low albedo. The Earth’s albedo varies mainly through benefits, costs, effectiveness, efficiency, and feasibility. v a r ying cloudiness, snow, ice, leaf area, and land-cover changes. Adaptation Benefits The avoided damage costs or the accrued benefits following Algal Blooms the adoption and implementation of adaptation measures. A reproductive explosion of algae in a lake, river, or ocean. Adaptation Costs Costs of planning, preparing for, facilitating, and implementing Alkalinity adaptation measures, including transition costs. A measure of the capacity of water to neutralize acids. Glossary of Terms 983 Allergens Arbovirus Antigenic substances capable of producing immediate-type Any of various viruses transmitted by arthropods and hypersensitivity. including the causative agents of dengue fever, yellow fever, and some types of encephalitis. Alpine The biogeographic zone made up of slopes above timberline Arid Regions and characterized by the presence of rosette-forming herbaceous Ecosystems with <250 mm precipitation per year. plants and low shrubby slow-growing woody plants. Autotrophic Alternative Risk Transfer Organisms independent of external sources of organic Capital-market alternatives to traditional insurance (e.g., carbon (compounds) for provision of their own organic c a tastrophe bonds). constituents, which they can manufacture entirely from i n o rganic material. Plants are autotrophic (photoautotrophs) Anadromous Species using the energy of sunlight to produce organic carbon A species of fish, such as salmon, that spawn in freshwater c o mpounds from inorganic carbon and water in the process then migrate into the ocean to grow to maturity. of photosynthesis. Anaerobic Baseflow Living, active, or occurring in the absence of free oxygen. Sustained flow in a river or stream that is primarily produced by groundwater runoff, delayed subsurface runoff, and/or Anoxia lake outflow. A deficiency of oxygen, especially of such severity as to result in permanent damage. Baseline/Reference The baseline (or reference) is any datum against which Antarctic Bottomwater change is measured. It might be a “current baseline,” in A type of water in the seas surrounding Antarctica with which case it represents observable, present-day conditions. t e mperatures ranging from 0 to -0.8°C, salinities from It might also be a “future baseline,” which is a projected 34.6 to 34.7 PSU, and a density near 27.88. This is the future set of conditions excluding the driving factor of densest water in the free ocean. in t e r est. Alternative interpretations of the reference conditions can give rise to multiple baselines. Antarctic Circumpolar Current A Southern Ocean current that flows around the entire globe Basin driven by the circumpolar westerlies. The drainage area of a stream, river, or lake. Antarctic Intermediate Water Benthic Organisms Created through large-scale cooling and Ekman convergence The biota living on, or very near, the bottom of the sea, in the Southern Ocean. river, or lake. Anthropogenic Biodiversity Resulting from or produced by human beings. The numbers and relative abundances of different genes (genetic diversity), species, and ecosystems AOGCM (communities) in a particular area. See also functional See climate model. diversity. Apex Consumers Biodiversity Hot Spots Organisms at the top of food chains; top predators. Areas with high concentrations of endemic species facing extraordinary habitat destruction. Aquaculture Breeding and rearing fish, shellfish, etc., or growing plants Biofuels for food in special ponds. A fuel produced from dry organic matter or combustible oils produced by plants. Examples of biofuel include alcohol (from Aquifer fermented sugar), black liquor from the paper manufacturing Astratum of permeable rock that bears water. An unconfined process, wood, and soybean oil. aquifer is recharged directly by local rainfall, rivers, and la k e s , and the rate of recharge will be influenced by the permeability Biomass of the overlying rocks and soils. A confined aquifer is The total mass of living organisms in a given area or c h a racterized by an overlying bed that is impermeable and volume; recently dead plant material is often included as the local rainfall does not influence the aquifer. dead biomass. 984 Glossary of Terms Biome Carbon Dioxide Fertilization A grouping of similar plant and animal communities into The enhancement of the growth of plants as a result of broad landscape units that occur under similar environmental increased atmospheric carbon dioxide concentration. conditions. Depending on their mechanism of photosynthesis, certain types of plants are more sensitive to changes in atmospheric Biosphere CO2 concentration. In particular, C3 plants generally show a The part of the Earth system comprising all ecosystems and larger response to CO2 than C4 plants. living organisms in the atmosphere, on land (terrestrial b i o sphere), or in the oceans (marine biosphere), including Carbon Flux derived dead organic matter, such as litter, soil org a n i c Transfer of carbon from one carbon pool to another in units m a tter, and oceanic detritus. of measurement of mass per unit area and time (e.g., t C). Biota Carrying Capacity All living organisms of an area; the flora and fauna considered The number of individuals in a population that the resources as a unit. of a habitat can support. Bog Catchment A poorly drained area rich in accumulated plant material, An area that collects and drains rainwater. frequently surrounding a body of open water and having a characteristic flora (such as sedges, heaths, and Chagas’Disease sphagnum). A parasitic disease caused by the Trypanosoma cruzi and transmitted by triatomine