Climate effects of China's efforts to improve its air quality

Facing severe air pollution issues, China has implemented a series of clean air policies aimed to improve the country's air quality. These policies largely focused on reducing emissions of major air pollutants such as sulfur dioxide (SO2) and primary aerosols. However, changes in such pollution also affect radiative forcing. To understand the climate consequences of these clean air actions in China, we evaluate the near-equilibrium climate response to sustained changes in aerosol (and precursors) emission rates equivalent to those that occurred in China between 2006 and 2017. During this period, China's SO(2)emissions declined by similar to 70%, and black carbon emissions declined by similar to 30%. Climate simulations that used a fully coupled ocean and atmosphere climate model indicate 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 a mean warming of 0.12 +/- 0.01 degrees C in the Northern Hemisphere; and may also affect the precipitation rates in East Asia and in more distant regions. The success of Chinese policies to further reduce aerosol emissions may bring additional net warming, and this 'unmasked' warming would in turn compound the challenge and urgency of international climate mitigation efforts.