Fossil fuel burning releases about 25 Pg of CO2 per year into the atmosphere, which leads to global warming (Prentice et al., 2001). However, it also emits 55 Tg S as SO2 per year (Stern, 2005), about half of which is converted to sub-micrometer size
sulfate particles, the remainder being dry deposited. Recent research has shown that the warming of earth by the increasing concentrations of CO2 and other greenhouse gases is partially countered by some backscattering to space of solar radiation by