Elsevier, Current Opinion in Environmental Sustainability, 4(2), p. 225-230
DOI: 10.1016/j.cosust.2010.06.008
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We estimatethenorthernhemisphere(NH)terrestrialcarbon sink bycomparingfourrecentatmosphericinversionswith land-based Caccountingdataforsixlargenorthernregions. The meanNHterrestrialCO2 sink fromtheinversionmodelsis 1.7 PgCyear1 over theperiod2000 2004. Theuncertaintyof this estimateisbasedonthetypicalindividual(1-sigma) precision ofoneinversion(0.9PgCyear1) andisconsistent with themin max rangeofthefourinversionmeanestimates (0.8 PgCyear1). Inversionsagreewithintheiruncertaintyfor the distributionoftheNHsinkofCO2 in longitude,withRussia being thelargestsink.Theland-basedaccountingestimateof NH carbonsinkis1.7PgCyear1 for thesumofthesixregions studied. The1-sigmauncertaintyoftheland-basedestimate (0.3 PgCyear1) issmallerthanthatofatmosphericinversions, but noindependentland-basedfluxestimateisavailableto derive a betweenaccountingmodel uncertainty. Encouragingly, thetop-downatmosphericandthebottom-up land-based methodsconvergetoconsistentmeanestimates within theirrespectiveerrors,increasingtheconfidenceinthe overall budget.Theseresultsalsoconfirmthecontinuedcritical role ofNHterrestrialecosystemsinslowingdownthe atmospheric accumulationofanthropogenicCO2