Local and remote mean and extreme temperature response to regional aerosol emissions reductions

• Published in: Atmospheric Chemistry and Physics
• Main Authors: D. M. Westervelt, N. R. Mascioli, A. M. Fiore, A. J. Conley, J.-F. Lamarque, D. T. Shindell, G. Faluvegi, M. Previdi, G. Correa, L. W. Horowitz
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2020
• Subjects: Physics; QC1-999; Chemistry; QD1-999; Arctic; Human health
• Online Access: https://doi.org/10.5194/acp-20-3009-2020; https://doaj.org/article/0772a3c5bf564f138147f2b74a999c36

The climatic implications of regional aerosol and precursor emissions reductions implemented to protect human health are poorly understood. We investigate the mean and extreme temperature response to regional changes in aerosol emissions using three coupled chemistry–climate models: NOAA GFDL CM3, NCAR CESM1, and NASA GISS-E2. Our approach contrasts a long present-day control simulation from each model (up to 400 years with perpetual year 2000 or 2005 emissions) with 14 individual aerosol emissions perturbation simulations (160–240 years each). We perturb emissions of sulfur dioxide ( SO 2 ) and/or carbonaceous aerosol within six world regions and assess the statistical significance of mean and extreme temperature responses relative to internal variability determined by the control simulation and across the models. In all models, the global mean surface temperature response (perturbation minus control) to SO 2 and/or carbonaceous aerosol is mostly positive (warming) and statistically significant and ranges from +0.17 K (Europe SO 2 ) to −0.06 K (US BC). The warming response to SO 2 reductions is strongest in the US and Europe perturbation simulations, both globally and regionally, with Arctic warming up to 1 K due to a removal of European anthropogenic SO 2 emissions alone; however, even emissions from regions remote to the Arctic, such as SO 2 from India, significantly warm the Arctic by up to 0.5 K . Arctic warming is the most robust response across each model and several aerosol emissions perturbations. The temperature response in the Northern Hemisphere midlatitudes is most sensitive to emissions perturbations within that region. In the tropics, however, the temperature response to emissions perturbations is roughly the same in magnitude as emissions perturbations either within or outside of the tropics. We find that climate sensitivity to regional aerosol perturbations ranges from 0.5 to 1.0 K ( W m −2 ) −1 depending on the region and aerosol composition and is larger than the climate sensitivity to a ...