Rising concentrations of greenhouse gases are the main drivers of current and projected future climate change. Reactive gases, including methane (CH4) and ozone (O3), contribute substantially to climate forcing and the chemistry controlling their abundances also responds to climate change. Using multiple global chemical transport models we diagnose factors controlling the year-to-year variations in tropospheric hydroxyl (OH), the main sink for atmospheric CH4. The modeled variations over the last decade are then evaluated against our best observational constraints. Using factors that control OH in the recent past, we project CH4 lifetime and abundance forward in time for a range of future climate scenarios. This simple approach agrees with projections from fully coupled Earth System Models. All this information is combined into an uncertainty analysis of the future CH4 abundance and global warming potential. Key process uncertainties are identified and can guide future research priorities.

Location: Physics Bldg., Room 401