A LARGE TERRESTRIAL CARBON SINK IN NORTH-AMERICA IMPLIED BY ATMOSPHERIC AND OCEANIC CARBON-DIOXIDE DATA AND MODELS

Atmospheric carbon dioxide increased at a rate of 2.8 petagrams of car bon per year (Pg C year(-1)) during 1988 to 1992 (1 Pg = 10(15) grams) . Given estimates of fossil carbon dioxide,emissions, and net oceanic uptake, this implies a global terrestrial uptake of 1.0 to 2.2 Pg C ye ar(-1). The spatial distribution of the terrestrial carbon dioxide upt ake is estimated by means of the observed spatial patterns of the grea tly increased atmospheric carbon dioxide data set available from 1988 onward, together with two atmospheric transport models, two estimates of the sea-air flux, and an estimate of the spatial distribution of fo ssil carbon dioxide emissions. North America is the best constrained c ontinent, with a mean uptake of 1.7 +/- 0.5 Pg C year(-1), mostly sout h of 51 degrees north. Eurasia-North Africa is relatively weakly const rained, with a mean uptake of 0.1 +/- 0.6 Pg C year(-1). The rest of t he world's land surface is poorly constrained, with a mean source of 0 .2 +/- 0.9 Pg C year(-1).