07 Jan 2021

07 Jan 2021

Review status: this preprint is currently under review for the journal ACP.

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

Ulas Im1,2, Kostas Tsigaridis3,4, Gregory Faluvegi3,4, Peter L. Langen1,2, Joshua P. French5, Rashed Mahmood6, Thomas Manu7, Knut von Salzen8, Daniel C. Thomas1,2, Cynthia H. Whaley8, Zbigniew Klimont9, Henrik Skov1,2, and Jørgen Brandt1,2 Ulas Im et al.
  • 1Department of Environmental Science, Aarhus University, Roskilde, Denmark
  • 2Interdisciplinary Centre for Climate Change, Aarhus University, Roskilde, Denmark
  • 3Center for Climate Systems Research, Columbia University, New York, NY, USA
  • 4NASA Goddard Institute for Space Studies, New York, NY, USA
  • 5Department of Mathematical and Statistical Sciences, University of Colorado Denver, USA
  • 6Barcelona Supercomputing Center, Barcelona, Spain
  • 7Swedish Meteorological and Hydrological Institute, Norrköping, Sweden
  • 8Candian Centre for Climate Modelling and Analysis, Environment and Climate Change Canada, Victoria, British Columbia, Canada
  • 9International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria

Abstract. The Arctic is warming two to three 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° N), using anthropogenic emissions from the Eclipse V6b and the Coupled Model Intercomparison Project Phase 6 (CMIP6) databases.

Surface aerosol levels, in particular black carbon (BC) and sulfate (SO42−), have been significantly underestimated by more than 50 %, with the smallest biases calculated for the nudged atmosphere-only simulations. CMIP6 simulations performed slightly better in simulating both surface concentrations of aerosols and climate parameters, compared to the Eclipse simulations. In addition, fully-coupled simulations had slightly smaller biases in aerosol levels compared to atmosphere only simulations without nudging.

Arctic BC, organic carbon (OC) and SO42− burdens decrease significantly in all simulations following the emission projections, with the CMIP6 ensemble showing larger reductions in Arctic aerosol burdens compared to the Eclipse ensemble. For the 2030–2050 period, both the Eclipse Current Legislation (CLE) and the Maximum Feasible Reduction (MFR) ensembles simulated an aerosol top of the atmosphere (TOA) forcing of −0.39±0.01 W m−2, of which −0.24±0.01 W m−2 were attributed to the anthropogenic aerosols. The CMIP6 SSP3-7.0 scenario simulated a TOA aerosol forcing of −0.35 W m−2 for the same period, while SSP1-2.6 and SSP2-4.5 scenarios simulated a slightly more negative TOA forcing (−0.40 W m−2), of which the anthropogenic aerosols accounted for −0.26 W m−2. Finally, all simulations showed an increase in the Arctic surface air temperatures both throughout the simulation period. In 2050, surface air temperatures are projected to increase by 2.4 °C to 2.6 °C in the Eclipse ensemble and 1.9 °C to 2.6 °C in the CMIP6 ensemble, compared to the 1990–2010 mean.

Overall, results show that even the scenarios with largest emission reductions lead to similar impact on the future Arctic surface air temperatures compared to scenarios with smaller emission reductions, while scenarios no or little mitigation leads to much larger sea-ice loss, implying that even though the magnitude of aerosol reductions lead to similar responses in surface air temperatures, high mitigation of aerosols are still necessary to limit sea-ice loss.

Ulas Im et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2020-1296', Anonymous Referee #1, 01 Mar 2021
  • RC2: 'Comment on acp-2020-1296', Anonymous Referee #2, 14 Mar 2021

Ulas Im et al.


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Short summary
Future (2015–2050) simulations of the aerosol burdens and their climate impacts over the Arctic under various emission projections show that although the Arctic aerosol burdens are projected to decrease significantly, the Arctic surface air temperatures will continue to increase by up to 2.6 °C in 2050. Regardless of the magnitude of aerosol reductions, similar responses in surface air temperatures are calculated, while high mitigation of aerosols are still necessary to limit sea-ice loss.