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

Abstract

Abstract. 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∘ N), using anthropogenic emissions from the Eclipse V6b and the Coupled Model Intercomparison 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 SO42- 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±0.01 W m−2, which is −0.08 W m−2 larger than the 1990–2010 mean forcing (−0.32 W m−2), of which -0.24±0.01 W m−2 was attributed to the anthropogenic aerosols. The CMIP6 ensemble simulated a RFARI of −0.35 to −0.40 W m−2 for the same period, which is −0.01 to −0.06 W m−2 larger than the 1990–2010 mean forcing of −0.35 W m−2. The scenarios with little to no mitigation (worst-case scenarios) led to very small changes in the RFARI, while scenarios with medium to large emission mitigations led to increases in the negative RFARI, mainly due to the decrease in the positive BC forcing and the decrease in the negative SO42- forcing. The anthropogenic aerosols accounted for −0.24 to −0.26 W m−2 of the net RFARI in 2030–2050 period, in Eclipse and CMIP6 ensembles, respectively. Finally, all simulations showed an increase in the Arctic surface air temperatures throughout the simulation period. By 2050, surface air temperatures are projected to increase by 2.4 to 2.6 ∘C in the Eclipse ensemble and 1.9 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 leads to similar impact on the future Arctic surface air temperatures and sea-ice extent compared to scenarios with smaller emission reductions, implying reductions of greenhouse emissions are still necessary to mitigate climate change.

Assessing the climate and air quality effects of future aerosol mitigation in India using a global climate model combined with statistical downscaling

“…For the anthropogenic aerosol emissions in ECHAM-HAMMOZ, we used the ECLIPSE V6b emission inventory (Stohl et al, 2015;Klimont et al, 2017;IIASA, 2021;Im et al, 2021) which was compiled with the integrated assessment model GAINS (Amann et al, 2011). For this study, we used only the emissions of BC, OC and sulfur dioxide (SO 2 ), and re-gridded the emission fields to correspond to the spatial grid resolution T63 used in ECHAM-HAMMOZ (∼2 °×2 • ).…”

“…In addition, we applied the trained random forest function to three separate climate model simulations which were conducted with present-day and future aerosol emission projections for the years 2015 and 2030, respectively. We used the ECLIPSE V6b emission scenarios, which project global emission changes for the current legislation (CLE) (Stohl et al, 2015) and for maximum feasible global mitigation of SLCFs (Im et al, 2021). Our aim was to simultaneously study the effects of global SLCF mitigation on Earth's energy balance and on air quality.…”

Spatiotemporal variations in summertime Arctic aerosol optical depth caused by synoptic-scale atmospheric circulation in three reanalyses

“…In addition to these two main influences on the atmosphere, absorbing aerosols can change the surface albedo over snow (Warren and Wiscombe, 1980) and sea ice (Perovich et al, 1998) areas, which would also contribute to accelerate the Arctic atmosphere warming. Comparable to warming by greenhouse gases and natural climate variability, Arctic aerosols affect the past (Aizawa et al, 2021) and future Arctic climate (Im et al, 2021). DeRepentigny et al (2022) showed that the interannual variability of biomass burning (BB) over the mid to high latitude has enhanced the sea ice decrease and the surface warming over the Arctic in the 21st century through nonlinear aerosol-cloud interactions and ice-albedo feedback.…”

Spring and summertime aerosol optical depth retrieval over the Arctic cryosphere by using satellite observations

“…In this way, aerosols also indirectly affect climate change (Twomey, 1977;Kaufman and Fraser, 1997;Hartmann et al, 2020). However, neither the contribution of aerosols to AA nor the effect of declining regional snow and ice on aerosol during the AA period is well understood (Im et al, 2021).…”