Climate Impacts From a Removal of Anthropogenic Aerosol Emissions.

B H Samset,C.‐F Schleussner,S Osprey,J S Fuglestvedt,M Sand,P M Forster,C J Smith,S E Bauer

doi:10.1002/2017gl076079

Abstract

Limiting global warming to 1.5 or 2.0°C requires strong mitigation of anthropogenic greenhouse gas (GHG) emissions. Concurrently, emissions of anthropogenic aerosols will decline, due to coemission with GHG, and measures to improve air quality. However, the combined climate effect of GHG and aerosol emissions over the industrial era is poorly constrained. Here we show the climate impacts from removing present-day anthropogenic aerosol emissions and compare them to the impacts from moderate GHG-dominated global warming. Removing aerosols induces a global mean surface heating of 0.5–1.1°C, and precipitation increase of 2.0–4.6%. Extreme weather indices also increase. We find a higher sensitivity of extreme events to aerosol reductions, per degree of surface warming, in particular over the major aerosol emission regions. Under near-term warming, we find that regional climate change will depend strongly on the balance between aerosol and GHG forcing.

Highlights

If global warming is to be kept within 1.5 or 2.0°C, strong, and rapid mitigation of anthropogenic greenhouse gas (GHG) emissions is required (Matthews & Caldeira, 2008; Millar et al, 2017; Rogelj, Luderer, et al, 2015)
We show how cleaning up aerosols, predominantly sulfate, may add an additional half a degree of global warming, with impacts that strengthen those from greenhouse gas warming
For all three major aerosol source regions, we find that the hottest day temperatures and maximum precipitation will change more for heating due to aerosol emission reductions than for a similar global warming due to greenhouse gases

Summary

Introduction

If global warming is to be kept within 1.5 or 2.0°C, strong, and rapid mitigation of anthropogenic greenhouse gas (GHG) emissions is required (Matthews & Caldeira, 2008; Millar et al, 2017; Rogelj, Luderer, et al, 2015). The combined climate effect of GHG and aerosol emissions over the industrial era is, poorly constrained (Bindoff et al, 2013; Boucher et al, 2013; Myhre, Shindell, et al, 2013). It is a reasonable expectation that the strongest radiative forcing will occur near emission regions, which are among the main populated regions of the globe. This indicates that the spatial details of emissions scenarios must be considered, rather than just the total radiative forcing and realized global warming (Wang et al, 2017)

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Results

Conclusion