Theabilityofforeststoabsorbman-madeCO2isweakeningaccordingtoananalysisoftwodecadesofdatafrommorethan30sitesinthefrozennorth.
ThestudywasconductedbyateamofCanadianChineseandEuropeanresearchersandpublishedinthesciencejournalNatureonJanuary3.ThefindingsmeanthatmoreoftheCO2wereleasewillendupaffectingtheclimateratherthanbeingsafelylockedawayintreesorsoil.
AsplantstakeupmoreCO2thatshouldputabreakonCO2increasesscientistsoncethought.Howeverthenewdatasuggestthatthisideaistoosimplified.Theresearchteammonitoredthedateinautumnatwhichtheforestsswitchedfrombeinganetsinkforcarbonintoanetsource.Insteadofmovinglaterintheyearastheyhadexpectedthisdateactuallygotearlier—insomeplacesbyafewdaysbutinothersbyafewweeks.
"Thismeanspotentiallyabiggerwarmingeffect"saidTimoVesalaiwholedthestudy.Thepreciseeffectthetrendwillhaveonfuturewarmingishardtopredict.ButtheresearchcouldpartlyexplainwhytheamountofCO2intheatmosphereisincreasingfasterthanexpected.
Currentlyhalfoftheman-madeCO2isabsorbedbyoceansandecosystemsonland.
Between1970and2000theCO2concentration(浓度)intheatmosphereroseby1.5ppm.Since2000theannualriseleaptoanaverageof1.9ppm—35%higherthanexpected.
InChinatheaveragetemperaturein2007was1.3℃higherthantheaveragetemperaturebetween1970and2000.
Soitistimeforustotakeactionnow.
1.Thewholepassageisintendedtotellusthat_________.
A.theaveragetemperatureisgettinghigher B.treesaretakinginlessCO2
C.theairisbecomingworseandworse D.theecosystemsonlandareharmful
2.Whatdoesthethirdparagraphmainlytellus?
A.PlantstakeupmoreCO2. B.Winterbecomeslaterwithspringearlier.
C.ForestsabsorblessCO2. D.PlantscanblockCO2increases.
3.Withwinterstartinglaterandspringearlierscientistsoncethought_________.
A.Plantswouldgrowbetterwithmoresunshine
B.Treeswouldsoakup