全球变暖-(英文)ppt课件

.,.,WhatisGlobalWarming?,Globalwarmingistheobservedcentury-scaleriseintheaveragetemperatureofEarthsclimatesystem.全球变暖是指全球气温在近一百年来不断上升，呈现变暖的趋势，这样一种气候变化特征。,.,Thecauseofglobalwarming,1.Naturalcause:Thegreenhouseeffect2.Humanreasons:Humanactivities,.,Thegreenhouseeffect,Thegreenhouseeffectisaprocessbywhichthermalradiationfromaplanetarysurfaceisabsorbedbyatmosphericgreenhousegases,andisre-radiatedinalldirections.Sincepartofthisre-radiationisbacktowardsthesurfaceandtheloweratmosphere,itresultsinanelevationoftheaveragesurfacetemperatureabovewhatitwouldbeintheabsenceofthegases.温室效应是一个过程,从行星表面热辐射被大气吸收温室气体,并再次辐射向四面八方。因为这部分再辐射回到地表和低层大气,它导致海拔平均表面温度高于没有这部分气体。,.,.,Humanactivities,1.Industrialwastegases2.Deforestation3.Trafficjam,.,Industrialwastegases,.,Deforestition,.,Trafficjam,.,Whatretheeffectsofglobalwarming,Negativeeffects1.Causethesealeveltorise2.Meltingglaciers3.Droughts4.Disappearanceofspecies,Positiveeffects1.makeplantsgrowfaster2.cropswillproducemore,.,Droughts,Iftheearthsaveragetemperature4degreesCelsius,theworldwillhavemorethan30millionpeoplewatershortages.如果地球平均气温上升4摄氏度，全球就会有30多亿人面临缺水问题。,.,Meltingglaciers,theearthspolesislandfatesnowmeltcanleadtorisingsealevels,manyislandswillbedrowned,someislandmaynotexist.地球两极冰雪融化会导致海平面上升，众多岛屿将被淹没，一些岛国可能不复存在。,.,So,le