Implications for CO2 emissions and sinks changes in western China during 1995-2008 from atmospheric CO2 at Waliguan.

Carbon dioxide (CO₂) emissions and sinks in western China are estimated and implied from atmospheric CO₂ measured at Waliguan during the period of 1995-2008. The observed CO₂ data are first classified as background, elevated, and sequestration, using a modified background identification method. Comparing it with two other methods tests the applicability of the method. By using this method, approximately 17.2%±1.2% and 10.1%±0.8% of all observed data are identified as elevated and sequestered CO₂, respectively, the percentages (occurrence rates) for both of which increased during 1995-2008. CO₂ emissions in western China have enhanced significantly in all seasons during the past 14 yr. Annual mean growth rates of CO₂ emissions in the region increased by ~8.4 Tg C yr^-1 (3.9% yr^-1) during 1995-2008 but accelerated after 2000 to ~12.6 TgC yr^-1 (6.2% yr^-1). The growth rates of CO₂ emission in western China are lower than the rest of the country. The annual mean emissions in the country during 1995-1999 and 2000-2006 are thought to be approximately 5.5 and 6.5 times higher than in western China, respectively. However, the growth rates of CO₂ emissions in western China are higher than global increase rates as reported by other studies. CO₂ sinks in western China varied from 86.0 Tg C yr^-1 in early 1995-1999 to 106.2 Tg C yr^-1 in 2005-2008. The most prominent change occurs in summer, indicating enhanced sequestration of photosynthetic CO₂ taken up by vegetation. The growth rates in sequestered CO₂ cannot keep up with the increase of CO₂ emissions in the region. If this continues, it could potentially impact on the global carbon budget. [ABSTRACT FROM AUTHOR]