A multiyear tropical Pacific cooling response to recent Australian wildfires in CESM2

The climate response to biomass burning emissions from the 2019-2020 Australian wildfire season is estimated from two 30-member ensembles using CESM2: one of which incorporates observed wildfire emissions and that does not. In response to the fires, an increase in biomass aerosol burdens across the southern hemisphere simulated through late 2019 and early 2020, accompanied by an enhancement of cloud albedo, particularly the southeastern subtropical Pacific Ocean. In turn, the surface cools, the boundary layer dries, and the moist static energy of the low-level flow into the equatorial Pacific is reduced. In response, the intertropical conver-gence zone migrates northward and sea surface temperature in the Nino3.4 region cools, with coupled feed-backs amplifying the cooling. A subsequent multiyear ensemble mean cooling of the tropical Pacific is simulated through the end of 2021, suggesting an important contribution to the 2020-2022 strong La Nina events.