Observed and Modeled Trends in Downward Surface Shortwave Radiation Over Land: Drivers and Discrepancies

Incoming surface shortwave radiation ((Formula presented.)) has exhibited regionally-variable multidecadal trends and variability over land that have variously been linked to aerosols and clouds. However, limitations in the spatiotemporal coverage of the observations, combined with apparent disagreements between climate models and observations, have precluded global analyses. Here, we first demonstrate that both the variability and trends in ERA5 (Formula presented.) agree favorably with high-quality estimates from satellite and in situ sources, and then show evidence of substantial continental brightening from 1980 to 2024, including in places like the central United States, Brazil, and central Asia that do not show large trends in aerosol concentrations over the same period. The brightening in these regions is co-located with reductions in total cloud cover, and trends in both are at the edge or entirely outside an ensemble of 237 CMIP6-era climate model simulations, whose spatial pattern of trends more directly reflect the pattern of aerosol concentrations.