IPCC_Managing Risks of Extreme Events.pdf - Climate Access

Annex IIGlossary of Termsdrought, also termed agricultural drought), and during the runoff andpercolation season primarily affects water supplies (hydrological drought).Storage changes in soil moisture and groundwater are also affected byincreases in actual evapotranspiration in addition to reductions inprecipitation. A period with an abnormal precipitation deficit is defined asa meteorological drought. A megadrought is a very lengthy and pervasivedrought, lasting much longer than normal, usually a decade or more.Early warning systemThe set of capacities needed to generate and disseminate timely andmeaningful warning information to enable individuals, communities, andorganizations threatened by a hazard to prepare and to act appropriatelyand in sufficient time to reduce the possibility of harm or loss.El Niño-Southern Oscillation (ENSO)The term El Niño was initially used to describe a warm-water currentthat periodically flows along the coast of Ecuador and Peru, disrupting thelocal fishery. It has since become identified with a basin-wide warmingof the tropical Pacific Ocean east of the dateline. This oceanic event isassociated with a fluctuation of a global-scale tropical and subtropicalsurface pressure pattern called the Southern Oscillation. This coupledatmosphere-ocean phenomenon, with preferred time scales of 2 toabout 7 years, is collectively known as the El Niño-Southern Oscillation.It is often measured by the surface pressure anomaly difference betweenDarwin and Tahiti and the sea surface temperatures in the central andeastern equatorial Pacific. During an ENSO event, the prevailing tradewinds weaken, reducing upwelling and altering ocean currents suchthat the sea surface temperatures warm, further weakening the tradewinds. This event has a great impact on the wind, sea surface temperature,and precipitation patterns in the tropical Pacific. It has climatic effectsthroughout the Pacific region and in many other parts of the world,through global teleconnections. The cold phase of ENSO is called La Niña.Emissions scenarioA plausible representation of the future development of emissions ofsubstances that are potentially radiatively active (e.g., greenhouse gases,aerosols), based on a coherent and internally consistent set of assumptionsabout driving forces (such as technological change, demographic andsocioeconomic development) and their key relationships. Concentrationscenarios, derived from emissions scenarios, are used as input to a climatemodel to compute climate projections. In the IPCC 1992 SupplementaryReport, a set of emissions scenarios was presented, which were used asa basis for the climate projections in the IPCC Second Assessment Report.These emissions scenarios are referred to as the IS92 scenarios. In theIPCC Special Report on Emissions Scenarios, new emissions scenarios, theso-called SRES scenarios, were published. SRES scenarios (e.g., A1B,A1FI, A2, B1, B2) are used as a basis for some of the climate projectionsshown in Chapter 3 of this report.EnsembleA group of parallel model simulations used for climate projections.Variation of the results across the ensemble members gives an estimateof uncertainty. Ensembles made with the same model but differentinitial conditions only characterize the uncertainty associated withinternal climate variability, whereas multi-model ensembles includingsimulations by several models also include the impact of modeldifferences. Perturbed parameter ensembles, in which model parametersare varied in a systematic manner, aim to produce a more objectiveestimate of modeling uncertainty than is possible with traditional multimodelensembles.EvapotranspirationThe combined process of evaporation from the Earth’s surface andtranspiration from vegetation.ExposureThe presence of people; livelihoods; environmental services and resources;infrastructure; or economic, social, or cultural assets in places that couldbe adversely affected.External forcingExternal forcing refers to a forcing agent outside the climate systemcausing a change in the climate system. Volcanic eruptions, solar variations,and anthropogenic changes in the composition of the atmosphere andland use change are external forcings.Extratropical cycloneAny cyclonic-scale storm that is not a tropical cyclone. Usually refers toa middle- or high-latitude migratory storm system formed in regions oflarge horizontal temperature variations. Sometimes called extratropicalstorm or extratropical low.Extreme coastal high water (also referred to as extreme sea level)Extreme coastal high water depends on average sea level, tides, andregional weather systems. Extreme coastal high water events areusually defined in terms of the higher percentiles (e.g., 90th to 99.9th)of a distribution of hourly values of observed sea level at a station for agiven reference period.Extreme weather or climate eventSee Climate extreme.FamineScarcity of food over an extended period and over a large geographicalarea, such as a country. Famines may be triggered by extreme climateevents such as drought or floods, but can also be caused by disease,war, or other factors.FloodThe overflowing of the normal confines of a stream or other body ofwater, or the accumulation of water over areas that are not normallysubmerged. Floods include river (fluvial) floods, flash floods, urbanfloods, pluvial floods, sewer floods, coastal floods, and glacial lakeoutburst floods.559