Negligible Contribution from Aerosols to Recent Trends in Earth’s Energy Imbalance

During the 21st century, Earth’s energy imbalance (EEI) at the top of the atmosphere has markedly increased, mainly due to an increase in absorbed shortwave (SW) rather than a decrease in outgoing longwave (LW) radiation. While previous studies, based on single-forcing (aerosol-only) experiments, linked reductions in anthropogenic aerosols to this positive SW trend, we find that both aerosol-radiation interactions and aerosol-cloud interactions have had a negligible impact on recent increases in the EEI. We estimate recent trends in effective radiative forcing due to aerosols using observations and reanalysis data. While aerosol concentrations have declined in the Northern Hemisphere (NH), wildfires and volcanic activity in the Southern Hemisphere (SH) have resulted in larger aerosol loading. This contrast effectively cancels out the total aerosol forcing, resulting in a negligible global impact on the EEI trend. Our findings also suggest that model-driven estimates may be overestimated, as they overlook the compensating effects of SH aerosol emissions that balance out NH reductions.