© 2002 Eugene S. Takle
Greenhouse gases lead to warming of the atmosphere due to absorption of infrared (not visible) radiation. Atmospheric aerosol (solid and liquid) particles lead to atmospheric cooling due to reflection back to space of visible solar radiation. But aerosols containing black carbon (soot from incomplete combustion) absorb a larger portion of visible solar radiation than other aerosol. This leads to warming in the region where, and during the time (weeks), these particles are suspended in the atmosphere. But the total effect is more complicated: the regional warming of the troposphere changes regional convection (vertical motion) patterns which, in turn, cause climate changes far from the aerosol cloud.
Black carbon enters the atmosphere from burning of both biomass (wood, agricultural wastes, etc.) and fossil fuels. Regulations in the US and most developed countries have reduced the amount of black carbon emitted in these countries, but some nations such as India and China emit large amounts of black carbon into the atmosphere (Chameides et al., 2002).
Menon et al (2002) have used the global climate model of the Goddard Institute for Space Studies (GISS) to estimate the impact of black carbon in the atmosphere. They find that large amounts of aerosol, including black carbon, emitted in China and India may well be responsible for recent increase in summer floods in south China and drought in north China. They also may be linked to surface temperature increases in Saudi Arabia, Sudan, western Africa, and central Canada as well as precipitation decreases in Saudi Arabia, and western Africa.
References
Chameides, W.L., and M. Bergin, 2002: Soot takes center stage. Science, 297, 2214-2215.
Menon, S., J. Hansen, l. Nazarenko, and Y. Luo, 2002: Climate effects of black carbon aerosols in China and India. Science, 297, 2250-2253.