Local and Remote Climate Responses to Regional Aerosol Perturbations: Initial Results from the RAMIP Experiments

The climatic implications of regional aerosol and precursor emissions reductions implemented to protect human health are poorly understood. However, quantitative estimates of climate responses to emission perturbations are needed by the climate assessment and impacts community. The Regional Aerosol Model Intercomparison Project (RAMIP) project builds on recent CMIP5-era studies to help address this knowledge gap. Briefly, RAMIP will use contrasting SSP aerosol emissions (SO2, BC, OC) scenarios (SSP3-7.0 and SSP1-2.6) to isolate the impact of realistic, near term aerosol changes on climate and air quality over rapidly developing regions of South Asia, East Asia, and Africa, and over North America and Europe. At least 9 CMIP6-generation global climate models are contributing to this new MIP, which uniquely focuses on specific regional aerosol emissions changes rather than simultaneous global changes. This presentation will specifically present the first results from the NASA Goddard Institute for Space Studies (GISS) ModelE contribution to RAMIP. We specifically use the GISS-E2.1-G version of the model, with one moment aerosols (OMA). All Tier 1 and Tier 2 simulations of RAMIP are included in the GISS contribution, with 10 ensembles for each simulation. Initial results at time of writing confirm the anticipated changes in aerosol optical depth, downwelling shortwave radiation, and aerosol mass concentration over each of the regions. The warming response to a decrease in SO2, BC, and OC is strongest in the US and Europe perturbation simulations, both globally and regionally, with Arctic warming up to 0.3 K due to a removal of US and European anthropogenic aerosol emissions alone; however, even emissions from regions remote to the Arctic, such as South Asian aerosols, can significantly warm the Arctic up to 0.2 K. In most regions, temperatures are most sensitive to emissions perturbations within that region. Arctic warming is the most robust model response across the regional aerosol emissions perturbations. Further results on precipitation and air quality response will be presented.