We need to talk about aerosols

1. Anthropogenic climate change is a global challenge, primarily caused by greenhouse gas emissions. While the warming impact of greenhouse gases is well understood, the climate effects of aerosols are less well characterized, contributing to large uncertainties in radiative forcing.
2. Aerosols generally cool the climate, either directly through interactions with solar radiation or by aerosol-cloud interactions. This results in the masking of global warming, thus contributing to net climate cooling.
3. Climate change mitigation policies that target emissions of longer-lived greenhouse gases will also decrease co-emitted “climate cooling” aerosols, which are much more shorter-lived and thus will decrease more quickly. This consequence of mitigation—demasking the aerosol cooling, will lead to net climate warming and thus inadvertently countering the intended impact.
4. The COVID-19 pandemic and the subsequent lockdowns provided a unique opportunity to empirically investigate and constrain the impacts of anthropogenic short-lived aerosols on the regional climate. The study found that the aerosol loading across South Asia decreased by as much as 18% following the COVID lockdown.
5. The decrease in aerosol loading led to an increase in radiative forcing by 1.4 Wm^2 when averaged over South Asia for the springtime. This is about three-fourths of the CO2 induced radiative forcing of 1.8 Wm^2.
6. Demasking the aerosol-induced surface cooling through climate mitigation actions will unveil the actual magnitude and effect of GHG-induced global warming; we shall anticipate a decades-long transitory increase in surface temperatures from planned mitigations.