Present and future aerosol impacts on Arctic climate change in the GISS-E2.1 Earth system model

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Im, Ulas, Tsigaridis, Kostas, Faluvegi, Gregory, Langen, Peter L., French, Joshua P., Mahmood, Rashed, Thomas, Manu, von Salzen, Knut, Thomas, Daniel C., Whaley, Cynthia H., Klimont, Zbigniew, Skov, Henrik, Brandt, Jorgen
• Format: Article in Journal/Newspaper
• Language: English
• Published: SMHI, Luftmiljö 2021
• Subjects: Meteorology and Atmospheric Sciences; Meteorologi och atmosfärforskning; Arctic; black carbon; Climate change
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:smhi:diva-6136; https://doi.org/10.5194/acp-21-10413-2021

The Arctic is warming 2 to 3 times faster than the global average, partly due to changes in short-lived climate forcers (SLCFs) including aerosols. In order to study the effects of atmospheric aerosols in this warming, recent past (1990-2014) and future (2015-2050) simulations have been carried out using the GISS-E2.1 Earth system model to study the aerosol burdens and their radiative and climate impacts over the Arctic (> 60 degrees N), using anthropogenic emissions from the Eclipse V6b and the Coupled Model Inter-comparison Project Phase 6 (CMIP6) databases, while global annual mean greenhouse gas concentrations were prescribed and kept fixed in all simulations. Results showed that the simulations have underestimated observed surface aerosol levels, in particular black carbon (BC) and sulfate (SO42-), by more than 50 %, with the smallest biases calculated for the atmosphere-only simulations, where winds are nudged to reanalysis data. CMIP6 simulations performed slightly better in reproducing the observed surface aerosol concentrations and climate parameters, compared to the Eclipse simulations. In addition, simulations where atmosphere and ocean are fully coupled had slightly smaller biases in aerosol levels compared to atmosphere-only simulations without nudging. Arctic BC, organic aerosol (OA), and SO(4)(2-)burdens decrease significantly in all simulations by 10 %-60% following the reductions of 7 %-78% in emission projections, with the Eclipse ensemble showing larger reductions in Arctic aerosol burdens compared to the CMIP6 ensemble. For the 2030-2050 period, the Eclipse ensemble simulated a radiative forcing due to aerosol-radiation interactions (RFARI) of -0.39 +/- 0.01Wm(-2), which is -0.08Wm(-2) larger than the 1990-2010 mean forcing (-0.32Wm(-2)), of which -0.24 +/- 0.01Wm(-2) was attributed to the anthropogenic aerosols. The CMIP6 ensemble simulated a RFARI of --0.35 to -0.40Wm(-2) for the same period, which is -0.01 to -0.06Wm(-2) larger than the 1990-2010 mean forcing of 0.35Wm(-2). The ...