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.