PIXE and micro-PIXE techniques were applied to study the effects of atmospheric aerosols on global warming/cooling. The average aerosol radiative forcing in Kyoto and Nagoya were 1.53 W/m2 (indicate cooling effect) and þ3.3 W/m2 (warming effect),respect ively. The difference of radiative forcing between the two cities may be caused by big differences in chemical composition of aerosols.