Assessing long-term changes in Aerosol Optical Depth (AOD) together with Aerosol Radiative Forcing Efficiency (ARFE, defined as radiative forcing per unit visible AOD) provides critical insight into the evolving role of different aerosol species in regional climate forcing. In this study, we analyse two decades of AOD trends (2001-2020) across eight climatically diverse regions using a multivariate regression framework, and quantify species-specific radiative effects with the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. The regions were chosen to represent contrasting trends in total AOD. Our results show that sulfate aerosols, which account for the largest share of AOD over India (similar to 36-45 %), are the primary driver of increasing AOD and associated atmospheric warming. Black carbon (BC), although contributing only a minor fraction to total AOD (2-10 %), emerges as the dominant warming agent across most regions, with particularly strong forcing signals over the Middle East. In contrast, sea-salt (SS) aerosols exert the largest cooling influence, most prominently over the Southern African (SAF) region, partially offsetting warming from absorbing species. Europe, despite an overall decline in AOD, exhibits a slight increase in SS that sustains a regional cooling effect. These findings demonstrate that species composition, vertical distribution, and optical properties govern ARFE more strongly than the total AOD magnitude alone. By linking AOD trends with species-resolved radiative forcing efficiency across multiple regions, this study advances the interpretability of ARFE as a climate indicator and highlights its potential to inform policy-relevant assessment of aerosol-driven warming and cooling.

来源平台：ATMOSPHERIC ENVIRONMENT