New Estimates of Aerosol Direct Radiative Effects and Forcing From A-Train Satellite Observations

Aerosol direct radiative effects are assessed using multi-sensor observations from the A-Train satellite constellation. By leveraging vertical cloud and aerosol information from CloudSat and CALIPSO, this study reports new global estimates of aerosol radiative effects and the component owing to anthropogenic aerosols. We estimate that the global mean aerosol direct radiative effect is -2.40W/m(2) with an error of 0.6W/m(2) owing to uncertainties in aerosol type classification and optical depth retrievals. Anthropogenic direct radiative forcing is assessed using new observation-based aerosol radiative kernels. Anthropogenic aerosols are found to account for 21% of the global radiative effect, or -0.50 0.3W/m(2), mainly from sulfate pollution (-0.54W/m(2)) partially offset by absorption from smoke (0.03W/m(2)). Uncertainty estimates effectively rule out the possibility that anthropogenic aerosols warm the planet, although strong positive forcing is observed locally where anthropogenic aerosols reside above clouds and bright surfaces.