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. 2018 Jan 28;45(2):1020-1029.
doi: 10.1002/2017GL076079. Epub 2018 Jan 8.

Climate Impacts From a Removal of Anthropogenic Aerosol Emissions

B H Samset  1 , M Sand  1 , C J Smith  2 , S E Bauer  3 , P M Forster  2 , J S Fuglestvedt  1 , S Osprey  4 , C-F Schleussner  5
Affiliations

Climate Impacts From a Removal of Anthropogenic Aerosol Emissions

B H Samset et al. Geophys Res Lett. .

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.

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Figures

Figure 1.
Figure 1.
Model responses to a removal of anthropogenic aerosol emissions. (left to right) Changes to surface temperature, precipitation, TXx, RX5D, and CDD. The solid bars show land area means; the hatched bars show global means. The yellow circles show changes over land, weighted by population density. The black bars show the multimodel mean responses.
Figure 2.
Figure 2.
Regional sensitivities to increases in (left column) long-lived GHG concentrations and (middle column) aerosol emission removal. (top row) Temperature. (bottom row) Precipitation. All panels show the mean of four models. (right column) The aerosol sensitivity ratio (ASR; see section 2). The hatched regions are where the multimodel mean is significantly different from the baseline mean, according to a two-tailed Student’s t test with p < 0.02 (see section 2). ASR is only plotted where both the GHG and aerosol change are statistically significant.
Figure 3.
Figure 3.
Extreme weather sensitivity to changes in (top row) long-lived GHG and (middle row) aerosol removal. Mean of four models. (bottom row) Aerosol response pattern (ASR). The hatching shows where all four models agree on the sign of the change. TXx: maximum daily temperature, annual mean. RX5D: maximum 5 day precipitation. CDD: consecutive dry days. ASR is only plotted where models agree on the sign of the change for both the GHG and aerosol simulations.
Figure 4.
Figure 4.
Land area mean changes to temperature, precipitation, and extreme weather indices, per degree of global mean surface temperature change. Globally (grey) and for three major aerosol emission regions (colors). The large circles show multimodel means; the small circles show individual model values. The left values are for GHG-induced warming; the right values (on yellow background) are for aerosol emission reductions.
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