An introduction to MethaneMIP: investigating the climate and health benefits of methane mitigation using Earth System Models

Methane is a potent greenhouse gas which has substantially contributed to climate change since the pre-industrial era, second only in importance to carbon dioxide. Due to its short atmospheric lifetime and high global warming potential, methane emissions have disproportionately large impacts on near-term climate change. Beyond its direct role as a greenhouse gas, methane also has other important implications for climate, human health, air quality and vegetation, largely due to its impact on tropospheric ozone. Thus, reducing methane emissions has been identified as a key policy lever for delaying the worst impacts of near-term climate change with expected co-benefits for health and air quality. The most notable of these efforts is the Global Methane Pledge which aims to achieve a 30% reduction in global anthropogenic methane emissions by 2030 as compared to 2020. And yet, in many respects, methane mitigation has been overlooked relative to other climate mitigation strategies. Existing modelling evidence for the estimating the potential climate benefits of methane mitigation rely extensively on idealised climate emulators or comprehensive modelling studies based on a limited number of models and ensemble members. Both approaches have important limitations. Hence, there is a pressing need for a co-ordinated intermodel comparison project which uses state-of-the-art ESMs in which all modelling groups prescribe identical reductions in methane concentrations or emissions, all modelling groups use the same baseline scenario, and sufficient ensemble members are simulated to investigate the broader climate and health impacts of methane mitigation. MethaneMIP has been envisioned to undertake these tasks.

In this talk I will introduce the MethaneMIP protocol and the two new methane reduction scenarios ‘Technical Measures’ and ‘Ambitious’, which are both branched from SSP2-4.5 and cover the period 2020-2050. The overarching aim of MethaneMIP is to provide a policy-relevant state-of-the-art estimate of the climate and health impacts of methane mitigation, and a robust quantification of the uncertainties, as well as furthering our understanding of methane’s role in the climate system. Over ten modelling centres from across the world are participating in MethaneMIP, with simulations for the core MethaneMIP experiments currently underway. For the first time, I will present the preliminary results of MethaneMIP as pertaining to the research questions it was set up to address, including: What are the best estimates of the expected climate and health benefits of plausible methane mitigation by mid-century? Which near-term climate events projected to occur may be delayed or avoided by curbing methane emissions? What are potential impacts of successful implementation of the Global Methane Pledge? When should we expect the climate or health signal from reduced methane to be detectable in the presence of internal variability?  I will finish by discussing the implications of MethaneMIP for climate policy, as well as introducing the flagship emissions-driven MethaneMIP simulations which will be performed later this year.