Radiative effects of reduced aerosol emissions during the COVID-19
pandemic and the future recovery
Abstract
The pandemic in 2020 caused an abrupt change in the emission of
anthropogenic aerosols and their precursors. We provide the first
estimate of the associated change in the aerosol radiative forcing at
the top of the atmosphere and the surface. To this end, we perform new
simulations with the contemporary Earth system model EC-Earth3
participating in CMIP6, and created new data on the anthropogenic
aerosol optical properties and an associated effect on clouds for the
implemented aerosol parameterization, MACv2-SP. Our results highlight
the small impact of the pandemic on the global aerosol radiative forcing
in 2020 compared to the baseline of the order of +0.04Wm-2, which is
small compared to the natural year-to-year variability in the radiation
budget. Natural variability also limits the ability to detect a
meaningful regional difference in the anthropogenic aerosol radiative
effects. We identify the best chances to find a significant change in
radiation at the surface during cloud-free conditions for regions that
were strongly polluted in the past years. The new post-pandemic recovery
scenarios indicate a spread in the aerosol forcing of -0.68 to -0.38Wm-2
for 2050, which translates to a difference of +0.05 to -0.25Wm-2
compared to the baseline. This spread falls within the present-day
uncertainty in aerosol radiative forcing and the CMIP6 spread in aerosol
forcing at the end of the 21st century. We release the new MACv2-SP data
for studies on the climate response to the pandemic and the recovery
scenarios.