水土保持专业英语.docx

水土保持专业英语

第一篇：水土保持专业英语W2GreenhousegasesandglobalwarmingKeynoteCarbondioxideconcentrationintheatmosphereCarbondioxide(CO2)isthemainvehicleofcarbonfluxbetweenatmosphere,oceansandbiota.Fossilfuels(coal,oilandnaturalgas)presentintheatmospherelaydormantuntilrecentcenturies.TheconcentrationofCO2intheatmospherehasincreasedfromabout280partspermillion(ppm)in1750toabout350ppmin1990andisstillrising,withthemainreasonfortheincreasebeingthecombustionoffossilfuels.EstimatesoffutureCO2emissions,andthecombustiontobeexpectedintheatmospherevary,butitappearslikelythattheconcentrationwillrisetoameanabout500ppmbytheyear2050.ThegreenhouseeffectThegreenhouseeffectisatheorywhichproposesthatpollutionbycommonanthropogenic(i.e.createdbyhumans)pollutantssuchasCO2andmethanemayleadtoanincreasedglobaltemperature.Overthelastcentury,CO2concentrationshaverisenandglobalairtemperatureshaveincreasedby0.4-0.7℃,whichsupportsthistheory.Theatmosphereformedaroundtheearthinsulatestheplanetfromfulleffectsofheatslossbytrappingheatintheatmosphereusinggreenhousegases,whichincludewatervaporaswellasCO2andotheranthropogenicpollutants.DoublingoftheatmosphericCO2concentrationfromitspresentlevelispredictedtoleadtoafurtherwarmingofaround3.5℃.RelatedtopicsSolarradiationandclimate(C1)Ozonedepletion(W3)Air,waterandsoilpollutants(W1)CarbondioxideconcentrationsintheatmospherePhotosynthesisandrespirationarethetwoopposingprocessesdrivingtheglobalcarboncycle.Itispredominantlyagaseouscycle,withCO2asthemainvehicleoffluxbetweenatmosphere,oceansandbiota.Historically,thelithosphereplayedonlyaminorrole;fossilfuels(coal,oilandnaturalgas)laydormantuntilrecentcenturies.TheconcentrationofCO2intheatmospherehasincreasedfromabout280(ppm)in1750toabout350ppmin1990andisstillrising.Since1958theatmosphereCO2concentrationhasrisenfrom315ppmto350ppmin1990(Fig.1).TheprincipalcauseoftheincreaseinatmosphericCO2inrecentyearshasbeenthecombustionoffossilfuels,whichin1990releasedabout5.5×109tonsofcarbonintotheatmosphere.Theexploitationofrainforesthasalsoc