Fewer aerosols may step up global warming
Photo by farl
Scientists believe they’ve seen a thinning of the aerosols found in Earth’s atmosphere.
That’s important because aerosols – which come from industrial pollution as well as natural causes – help shield us from the effects of global warming. Some refer to them as a global “sunscreen.” Aerosols cool Earth by reflecting sunlight. So, fewer aerosols mean more warming.
Earth & Sky spoke to Michael Mishchenko at the Goddard Institute of Space Studies in New York. His study shows a decrease in aerosols in the lower atmosphere since 1991.
Michael Mishchenko: All of a sudden we saw a change in the background value, globally by as much as 20 percent. And this is a very significant change.
With fewer aerosols, the effects of global warming will be felt more intensely, according to Mishchenko.
A reason for the decrease may be the steps taken in the 1970s by industrialized nations to curb emissions.
Mishchenko: There are fewer particles to reflect the sunlight and so the global warming produced by the greenhouse gases … may have become more obvious because of this decrease in aerosols.
He also said Earth’s temperature is increasing now at a faster rate than the models predicted some time ago. It could be that those models didn’t take the potential for this aerosol decrease into account.
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Referring to national efforts to curb industrial emissions at the end of the 1970s, Mishchenko added, “In this case, we believe that this change in aerosol amount is a man-made change, most likely. Simply because, if you look at what happened to the countries of the former Soviet Union and what is the effect of the Clean Air Acts in the United States and in Europe, this combined effect was to reduce the amount of aerosols.”
He continued, “If you look at what we can do to aerosols on a global basis and what the effect of this change may be, you can start to believe in global warming being the result of human activities.”
Scientists will have more answers when NASA launches an instrument designed to determine the composition of the aerosols – whether they’re natural or manmade – at the end of 2008. It will be part of NASA’s Glory mission.
Global ‘Sunscreen’ Has Likely Thinned, Report NASA Scientists
Our thanks to:
Michael Mishchenko
Senior Scientist
NASA Goddard Institute for Space Studies
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