December 8, 2009

Network Observation At The GAW Stations And Atmospheric CO2 Mixing Ratios Over China

Carbon dioxide (CO2) is the most important greenhouse gas regulated by the Kyoto Protocol. Human activities, such as fossil fuel burning and land use change, are major emitters of CO2, which is widely recognized as drivers of global warming and climate change. In the past decades, the field campaign and research program were only conducted at a few sites in China by different agencies. However, none of those measurements could effectively document spatial and temporal distributions of atmospheric CO2 and provide essential information for our understanding of regional differences and distributions over China. Thus, it is essential to establish a long-term observational network at multiple sites and carefully calibrate on internationally agreed reference scales with better quality controls.

Chinese Academy of Meteorological Sciences in Beijing initiated network observation at the four Global Atmosphere Watch (GAW) stations in China: Waliguan (36.29ºN, 100.90ºE, 3816m asl) in remote western China, Shangdianzi (40.39ºN, 117.07ºE, 293.9m asl) in northeast Beijing, Lin'an (30.3ºN, 119.73ºE, 138m asl) in Yangtze Delta, and Longfengshan (44.73ºN, 127.6ºE, 310m asl) in northeastern China. It shows for the first time the atmospheric CO2 mixing ratios and regional differences based on internationally recognized weekly air sampling data from September 2006 to August 2007. The study is reported in Issue 52 (November, 2009) of Science in China Series D: Earth Sciences.

World Meteorological Organization (WMO) through its Global Atmosphere Watch (GAW) Program, coordinates the observations of greenhouse gases in the atmosphere through a network of stations located in more than 50 countries. According to its 5th Greenhouse Gases Bulletin announced on 23 November 2009, the globally averaged mixing ratio of atmospheric CO2 in 2008 was 385.2ppm (number of molecules of the gas per million molecules of dry air), with an increase of 2.0ppm from the previous year, continuing the trend of exponential increase. Since 1750, atmospheric CO2 has increased by 38% primarily because of emissions from combustion of fossil fuels, deforestation, and land use change, contributing 63.5% to the increase in overall radiative forcing. The Bulletins provide critical information on the global state of the atmosphere in a concise manner and highlight recent accomplishments of research and technology application. The 2008 Bulletin precedes the 15th session of the United Nations Framework Convention on Climate Change (Copenhagen, 7-18 December 2009).

Long-term observation since 1990 at Waliguan GAW global station in western China validated comparable atmospheric CO2 mixing ratios to that of other global background stations in the world. The data were widely used by the WMO Greenhouse Gases Bulletins and series of scientific reports such as IPCC assessments. Results from this study further shows that atmospheric CO2 mixing ratios at Waliguan, Shangdianzi, Lin'an, and Longfengshan were 383.5, 385.9, 387.8, and 384.3 ppm, respectively, during the research period from September 2006 to August 2007. The atmospheric CO2 mixing ratio at the Waliguan station changed slightly. However, it changed sharply at the Shangdianzi and the Lin'an stations due to great influence of human activities in the Jingjinji and the Changjiang Delta economic zones, and changed regularly with seasons at Longfengshan station under dual influences of human activities and plant photosynthesis. The results from this study could lay the foundation for more profound studies in different areas of China, and could be used to improve the understanding of carbon source and sink distribution.


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