Smoke ‘Parasol’ May Be Retarding Global Warming

A global shade caused by smoke from burning tropical forests and grassland is delaying the predicted greenhouse warming of the Earth, perhaps by a few decades, researchers say.

Emissions from the burning of up to 5 billion tons of plant matter annually act like a parasol for the planet, Joyce E. Penner of Lawrence Livermore National Laboratory in California said Thursday.

Most scientists believe that carbon dioxide and some other gases in the atmosphere cause heat to be trapped about the planet.

Smoke and other aerosols in the atmosphere, however, help block sunlight. But Penner warned that the effect will not save the Earth from the eventual temperature rises predicted as the result of too much carbon dioxide in the atmosphere.

In a report to be published today in the journal Science, Penner and researchers at the University of Arizona conclude that there is enough smoke from burning biomass to explain why the global temperatures have not risen as rapidly as scientists had forecast under the greenhouse theory.