• Main Authors: Atmospheric Methane, Jos Lelieveld, Paul J. Crutzen
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1997
• Subjects: ice core
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.458.5263; http://tellusb.net/index.php/tellusb/article/download/16030/17945/

Previous studies on ice core analyses and recent in situ measurements have shown that CH4 has increased from about 0.75 to 1.73 mmol/mol during the past 150 years. Here, we review sources and sink estimates and we present global 3D model calculations, showing that the main features of the global CH4 distribution are well represented. The model has been used to derive the total CH4 emission source, being about 600 Tg yr−1. Based on published results of isotope measure-ments the total contribution of fossil fuel related CH4 emissions has been estimated to be about 110 Tg yr−1. However, the individual coal, natural gas and oil associated CH4 emissions can not be accurately quantified. In particular natural gas and oil associated emissions remain speculative. Since the total anthropogenic CH4 source is about 410 Tg yr−1 (~70 % of the total source) and the mean recent atmospheric CH4 increase is ~20 Tg yr−1 an anthropogenic source reduction of 5 % could stabilize the atmospheric CH4 level. We have calculated the indirect chemical eVects of increasing CH4 on climate forcing on the basis of global 3D chemistry-transport and radiative transfer calculations. These indicate an enhancement of the direct radiative eVect by about 30%, in agreement with previous work. The contribution of CH4 (direct and indirect eVects) to climate