Estimation of carbon dioxide emission in Beijing city

In order to evaluate the impact of urbanization on carbon cycle, we selected the Beijing city as the study area to estimate CO₂ emission both from anthropogenic activity and natural processes. The spatial pattern of annual CO₂ emission in 1992 and 2005 in Beijing city was estimated by using the socioeconomic statistical data, remote sensing data and GIS-based approach. The main factors include transport, cement production, human respiration, carbon assimilation of green space and cropland. The vehicle density was determined by combining the remote sensing images from Google-Earth with road map and statistical data. The human respiration was estimated from census data and allocated to different districts. In order to estimate the impact of land use/land cover change on carbon absorption, we first extracted the green space and cropland from Landsat TM data in 1992 and 2005 by using maximum likelihood method. The annual carbon assimilation of green space and cropland was estimated finally according to the carbon flux observation in green space and the simulated results for cropland by using Biome-BGC model. The results showed that the vehicles and industry contributed most in Beijing city. The total CO₂ emission had increased about 1.7 times from 16,232.99 kiloton in 1992 to 28,091.93 kiloton in 2005. The increase of green space can partly compensate the decrease of cropland caused by urbanization at a certain extent.