This paper provides the first climatology from satellite of aerosol loading, both over land and oceanic surfaces. Over land, aerosol loading is retrieved using a new remote sensing technique based on the polarization signature of scattered solar radiances. The product is sensitive to particles that are within the accumulation mode, smaller than ≈0.5 &mgr;m. Those are mainly produced by anthropogenic sources, like smoke and urban/industrial aerosols. A rough identification of aerosol origin is obtained from the concomitant detection of fires from spaceborne observations. The combination of aerosol load and fire identification suggests that biomass burning is the main source of small particles in the atmosphere and that, at the regional scale, other anthropogenic activities have a significant impact limited to China and India. ¿ 2001 American Geophysical Union