|2011-05-22 15:28:53||Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions|
Courtesy of Leland Palmer:
Here we apply a “state of the art” atmospheric chemistry transport model to show that large emissions of CH4 would likely have an unexpectedly large impact on the chemical composition of the atmosphere and on radiative forcing (RF). The indirect contribution to RF of additional methane emission is particularly important. It is shown that if global methane emissions were to increase by factors of 2.5 and 5.2 above current emissions, the indirect contributions to RF would be about 250% and 400%, respectively, of the RF that can be attributed to directly emitted methane alone.
Assuming several hypothetical scenarios of CH4 release associated with permafrost thaw, shallow marine hydrate degassing, and submarine landslides, we find a strong positive feedback on RF through atmospheric chemistry. In particular, the impact of CH4 is enhanced through increase of its lifetime, and of atmospheric abundances of ozone, stratospheric water vapor, and CO2 as a result of atmospheric chemical processes. Despite uncertainties in emission scenarios, our results provide a better understanding of the feedbacks in the atmospheric chemistry that would amplify climate warming.
Radiative forcing resulting from CH4 increases. Blue bars denote contributions from direct emissions, and red bars are contributions from CH4 initiated changes in atmospheric composition. “CH4 indirect” represents the CH4 enhancement that is due to the increase in its lifetime. “CO2 indirect” relates to the CO2 enhancement due to oxidation of the additional CH4. The lightest colors refer to the 4 × CH4, medium light colors to the 7 × CH4 and dark colors to the 13 × CH4 case. The radiative forcing is not related to a particular year but to the time when the CH4 increase is reached. The 13 × CH4 case refers to a shorter time horizon (30 years) while the other cases are based on a 50 year time horizon.
Citation: Isaksen, I. S. A., M. Gauss, G. Myhre, K. M. Walter Anthony, and C. Ruppel (2011), Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions, Global Biogeochem. Cycles, 25, GB2002,