Asia, as one of the biggest Northern Hemisphere terrestrial carbon sinks, has a significant impact on the global carbon budget. It is estimated that Asian ecosystems contribute over 50% of the global net terrestrial ecosystem exchange (NEE). However, estimates of the terrestrial carbon fluxes in Asia show large uncertainties particularly in the boreal and mid-latitudes and in China due to the limited numbers of observation.

To improve estimates of Asian terrestrial fluxes, Prof. CHEN Baozhang and his team, at the Institute of Geographic Sciences and Natural Resources Research (IGSNRR) performed atmospheric CO2 inversion CarbonTracker using passenger aircraft based measurements of the Comprehensive Observation Network for Trace gases by Airliner (CONTRAIL) project, in addition to the global network of surface concentration measurements of the National Oceanic and Atmospheric Administration (NOAA).

The results showed that the averaged annual total Asian terrestrial land CO₂ sink was about -1.56±1.34 Pg C yr^-1 (1-sigma Gaussian error) over the period 2006–2010, with carbon uptake of -0.77±0.81, -0.44±0.48, -0.20±0.48 Pg C yr^-1 (carbon sinks were referred with a negative sign) in forests lands, grass/shrub lands and croplands. The peak-to-peak amplitude of inter-annual variability (IAV) in Asian NEE was 0.57 Pg C yr^-1 ranging from -1.71 Pg C yr^-1 to -2.28 Pg C yr^-1. The IAV analysis reveals that the Asian CO₂ sink was sensitive to climate variations, with the lowest uptake in 2010 concurrent with a summer flood and autumn drought and the largest CO2 sink in 2009 owing to favorable temperature and plentiful precipitation conditions.

They also found the inclusion of the CONTRAIL data in the inversion modeling system reduced the uncertainty by 11% over the whole Asian region, with a large reduction in the southeast of boreal Eurasia, southeast of temperate Eurasia and most tropical Asian areas.

This work has been published in Atmoshperic Chemistry and Physics in June, 2014.