The role of an interactive methane cycle in climate sensitivity and climate feedbacks

Despite methane’s importance as a greenhouse gas, the Earth System Models that contributed to Phase 6 of the Coupled Model Intercomparison Project (CMIP6) typically prescribe surface methane concentrations - following either historical observations or specified future shared socioeconomic pathways. Here, we make use of novel methane emissions-driven capability in the UK’s Earth System Model to explore the role of an interactive methane cycle, including wetland emissions, on the model’s equilibrium climate sensitivity and its transient climate response to changes in carbon dioxide concentration.

The climate response to external forcings is strongly influenced by climate feedbacks and with the inclusion of interactive methane in Earth System Models, it becomes important to understand the effects of changing carbon dioxide and meteorology on wetland emissions.  This work re-evaluates the CMIP6 assessment of the methane wetland emissions feedback in UKESM1 by taking account of wetland emissions’ sensitivity to both meteorology and carbon dioxide. 

This presentation demonstrates the need for including interactive methane in Earth System Models. By allowing changes in natural methane emissions to influence methane concentrations and climate, this novel capability enables scientists to determine the consequences of methane emission reduction policies or climate feedbacks on natural methane sources towards meeting global climate as well as global air quality targets.