ALBERT

Description: [1]  Natural carbon sources and sinks over China's terrestrial land ecosystems have an uncertain magnitude, but possibly an important role in the global carbon budget. In this paper we present an estimate of net ecosystem exchange of CO 2 (NEE) over China for the years 2001-2010 using the CarbonTracker Data Assimilation System for CO 2 (CTDAS). Additional Chinese and Asian CO 2 observations are used in CTDAS to improve our estimate. We found that the combined terrestrial ecosystems in China absorbed about –0.33 Pg Cy r -1 during 2001-2010, compensating approximately 20% of the total CO 2 emissions from fossil fuel burning and cement manufacturing from China (+1.70 Pg C yr -1 ). The uncertainty on Chinese terrestrial carbon exchange estimates as derived from a set of sensitivity experiments suggests a range of –0.29 to –0.64 Pg C yr -1 . This total Chinese terrestrial CO 2 sink is attributed to the three major biomes (forests, crop lands and grass/shrub lands) with estimated CO 2 fluxes of –0.12 Pg C yr -1 (range from –0.09 to –0.19 Pg C yr -1 ), –0.12 Pg C yr -1 (range from –0.09 to –0.26 Pg C yr -1 ) and –0.09 Pg C yr -1 (range from –0.09 to –0.17 Pg C yr -1 ), respectively. The peak-to-peak amplitude of inter-annual variability (IAV) of the Chinese terrestrial ecosystem carbon flux is 0.21 Pg C yr -1 (~64% of mean annual average), with the smallest CO 2 sink (–0.19 Pg C yr -1 ) in 2003 and the largest CO 2 sink (–0.40 Pg C yr -1 ) in 2007 corresponding with favorable temperature in spring/winter. We stress that our estimate of terrestrial ecosystem CO 2 uptake based on inverse modeling strongly depends on a limited number of atmospheric CO 2 observations used. More observations in China specifically, and in Asia in general are needed to improve the accuracy of terrestrial carbon budgeting for this region.