Geophys. Res. Lett. 48, e2021GL093841 (2021)

Levels of particulates in the atmosphere can affect the surface temperature, as a high particulate load reduces warming. In 2020, two events had an effect on the particulate load; the end of 2019 and start of 2020 saw large parts of Australia burning as severe wildfires swept across the land, pumping emissions and particulate matter into the atmosphere, whereas the pandemic-related lockdowns reduced emissions.

Using the Community Earth System Model v2, John Fasullo and colleagues from the National Center for Atmospheric Research, Boulder, CO, USA, estimate the climate response to these events. The 50-member ensemble simulations show that the Australian fires resulted in a brightening of clouds, peaking in late 2019, and an associated global cooling of 0.06 ± 0.04 °C by mid-2020; a more gradual response was seen from COVID-19-related reductions, with warming of 0.05 ± 0.04 °C by the end of 2022.

These results show the impact of these different events on top of atmospheric radiative balance and resultant responses in temperature, offering insight into how global and regional climate respond to particulate and emission changes.