Regional warming from aerosol removal over the United States: Results from a transient 2010–2050 climate simulation

We use a general circulation model (NASA Goddard Institute for Space Studies GCM 3) to investigate the regional climate response to removal of aerosols over the United States. We perform a pair of transient 2010–2050 climate simulations following a scenario of increasing greenhouse gas concentrations, with and without aerosols over the United States and with present-day aerosols elsewhere. We find that removing U.S. aerosol significantly enhances the warming from greenhouse gases in a spatial pattern that strongly correlates with that of the aerosol. Warming is nearly negligible outside the United States, but annual mean surface temperatures increase by 0.4–0.6 K in the eastern United States. Temperatures during summer heat waves in the Northeast rise by as much as 1–2 K due to aerosol removal, driven in part by positive feedbacks involving soil moisture and low cloud cover. Reducing U.S. aerosol sources to achieve air quality objectives could thus have significant unintended regional warming consequences.

► We perform two 2010–2050 climate simulations to examine the climate response to US aerosol removal.
► Removing US aerosols causes surface temperatures to increase by 0.4–0.6 K in the eastern US.
► Temperatures during summertime heat waves in the Northeast rise by as much as 1–2 K.
► The warming in the Northeast is amplified by feedbacks involving cloud cover and soil moisture.
► Reducing US aerosol sources to achieve air quality goals may lead to unintended regional warming.