In this paper we present an estimate of net ecosystem CO 2 exchange 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 À0.33 Pg C yr À1 during 2001-2010. The uncertainty on Chinese terrestrial carbon exchange estimates as derived from a set of sensitivity experiments suggests a range of À0.29 to À0.64 Pg C yr À1 . This total Chinese terrestrial CO 2 sink is attributed to the three major biomes (forests, croplands, and grass/shrublands) with estimated CO 2 fluxes of À0.12 Pg C yr À1 (range from À0.09 to À0.19 Pg C yr À1 ), À0.12 Pg C yr À1 (range from À0.09 to À0.26 Pg C yr À1 ), and À0.09 Pg C yr À1 (range from À0.09 to À0.17 Pg C yr À1 ), respectively. The peak-to-peak amplitude of interannual variability of the Chinese terrestrial ecosystem carbon flux is 0.21 Pg C yr À1 (~64% of mean annual average), with the smallest CO 2 sink (À0.19 Pg C yr À1 ) in 2003 and the largest CO 2 sink (À0.40 Pg C yr À1 ) in 2007. 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.

Sensible heat flux (H), latent heat flux (LE), and net radiation (NR) are important surface energy components that directly influence climate systems. In this study, the changes in the surface energy and their contributions from global climate change and/or land-cover change over eastern China during the past nearly 30 years were investigated and assessed using a process-based land surface model [the Ecosystem–Atmosphere Simulation Scheme (EASS)]. The modeled results show that climate change contributed more to the changes of land surface energy fluxes than land-cover change, with their contribution ratio reaching 4:1 or even higher. Annual average temperature increased before 2000 and reversed thereafter; annual total precipitation continually decreased, and incident solar radiation continually increased over the past nearly 30 years. These climatic changes could lead to increased NR, H, and LE, assuming land cover remained unchanged during the past nearly 30 years. Among these meteorological variables, at spatial distribution, the incident solar radiation has the greatest effect on land surface energy exchange. The impacts of land-cover change on the seasonal variations in land surface heat fluxes between the four periods were large, especially for H. The changes in the regional energy fluxes resulting from different land-cover type conversions varied greatly. The conversion from farmland to evergreen coniferous forests had the greatest influence on land surface energy exchange, leading to a decrease in H by 19.39% and an increase in LE and NR by 7.44% and 2.74%, respectively. The results of this study can provide a basis and reference for climate change adaptation.

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