Patrick Jöckel (DLR) will join us next week on Thursday, 5 September to give a seminar.

The role of atmospheric methane lifetime for methane induced feedbacks on atmospheric chemistry and climate

Methane is the second most important greenhouse gas directly emitted by human activity. Its removal from the atmosphere, mainly by chemical decomposition (oxidation), determines its atmospheric lifetime to about a decade. The atmospheric lifetime of methane is, however, not constant, but depending on temperature (and thus the climate state), and on the abundance of the reaction partners, mainly the hydroxyl radical (OH). Furthermore, the abundance of methane itself strongly affects its lifetime.  Since moreover both, natural and anthropogenic emission fluxes are still subject to large uncertainties, in most chemistry climate model simulations (e.g. CCMI and CMIP), methane mixing ratios instead of emission fluxes are prescribed at the lower model boundary, in order to represent the observed methane time series between pre-industrial time and present. This method, however, suppresses important feedbacks of increasing methane emissions on atmospheric chemistry and climate.

The presentation will provide an overview about results obtained with our EMAC chemistry climate model addressing the role of methane and its induced feedbacks on atmospheric chemistry and climate.