In the remote-sensing experiments of CO2 in Beijng, the authors found that the higher concentration of CO2 in autumn is caused by the CO2 emission by the traffic sector during the day time. During the day time, the concentratration of CO2 is comparatively lower because of the photochemistry and the transportation of troposphere. And the concentration of CO2 is about 410 microg x mL(-1). At night the fossil fuel power plants will be taken as a model for the source of CO2, so the concentration of CO2 is about 610 microg x mL(-1) or higher. The carbon increment from increased photosynthesis is greater than the increment in ecosystem carbon stocks. The higher the temperature, the lower the CO2 concentration. And the lower the rate of wind, the higher the concentration of CO2 also. Besides, the concentration of CO2 is affected by some other weather factors.