Climate Effects of Aerosol Abatement in China and Beyond

Abstract:

Anthropogenic aerosols have long been regarded as a major threat to air quality and public health. Globally, aerosols are estimated to cause 5.6 to 8.9 million premature deaths each year, with between one quarter and one third of these deaths occurring in China. Policies have been taken by the developed economies, and in the most recent decade by China, to reduce aerosol emissions to protect public health.

Using a fully coupled ocean and atmosphere climate model, we provide evidence that China’s reductions in aerosol emission rates from 2006 to 2017 may exert a net increase in global radiative forcing of 0.09 ± 0.03 W m^-2 and which in a near-equilibrium state would produce a mean warming of 0.12 ± 0.01 °C throughout the northern hemisphere—not just in China itself. These large-scale temperature responses are also true for the complete removal of global anthropogenic aerosol emissions. By using the same climate model, we found that removing global anthropogenic aerosol emissions may unmask 0.72 ± 0.02 °C of global mean greenhouse gases-induced warming in the year 2010, with evident warming effects over nearly all land areas.

Recent empirical analyses have concluded that warming harms economies in warm climates, but provides economic benefits in cold climates. This evidence suggests that the unmasked warming induced by the removal of global anthropogenic aerosol emissions may benefit developed high-latitude economies while harming developing tropical economies, and may thus exacerbate global economic inequality. Further investigation illustrates that the regional distribution of climate effects of aerosol emissions changes is strongly influenced by the background state of the climate system. Our results indicate that the climate effects of efforts reduce aerosol emissions can exacerbate global economic inequality. However, health benefits of aerosol emission reductions are very large and often benefit those with the least material well-being; thus the overall effect of aerosol emissions abatement is very likely to reduce inequality.