Publication

Aerosol impact on the surface temperature varies between the shortwave and the longwave components of radiation, depends on the time of the day, and is modulated by underlying biophysical processes. We disentangle these complexities by isolating the direct surface shortwave and longwave radiative effects from a global reanalysis data product and calculating their spatially explicit climate sensitivities. Higher sensitivity is found for the longwave component and is driven by a combination of spatial variability of aerosol species and biophysical control of the underlying surface. The opposing shortwave and longwave effects reduce the global mean diurnal temperature range by 0.47 K, with almost half the contribution coming from aerosols of anthropogenic origin. We also find evidence of an increasing trend in the local climate sensitivity in the equatorial zone, possibly caused by deforestation. These surface processes can partially explain why the climate forcing efficacy of aerosols exceeds unity. Plain Language summary The radiative effect of aerosols is disproportionately stronger at the Earth's surface compared to the top of the atmosphere and depends on the time of the day and aerosol properties. Moreover, the local surface temperature response to aerosols depends on both incoming energy and the surface energy dissipation via the properties of the underlying surface. To disentangle these complex interactions, we use a theoretical framework to separate surface temperature response to the aerosol shortwave and longwave radiative effects for the world's land surfaces using a reanalysis dataset. We find a stronger local climate sensitivity to the longwave radiative effect than to the shortwave. This is partly due to the incidental collocation of regions of high local climate sensitivity with regions containing coarse mineral dust aerosols. The opposite directions of the surface shortwave and longwave radiative effects reduce the diurnal temperature range, particularly in arid regions. Long-term trends show an intensification of the local climate sensitivity in the tropics due to deforestation, demonstrating the importance of local biophysical processes in aerosol-climate interactions. The addition of this biophysical control may partially explain why the global climate sensitivity to aerosols is stronger than that due to well-mixed greenhouse gases.