16 March 2007: A new NASA study has found that an important counter-balance to the warming of our planet by greenhouse gases sunlight blocked by dust, pollution and other aerosol particles appears to have lost ground.
The thinning of Earth’s “sunscreen” of aerosols since the early 1990s could have given an extra push to the rise in global surface temperatures. The finding, published in the journal Science, may lead to an improved understanding of recent climate change. In a related study published last week, scientists found that the opposing forces of global warming and the cooling from aerosol-induced ‘global dimming’ can occur at the same time.
“When more sunlight can get through the atmosphere and warm Earth’s surface, you’re going to have an effect on climate and temperature,” said lead author Michael Mishchenko of NASA’s Goddard Institute for Space Studies (GISS), New York. “Knowing what aerosols are doing globally gives us an important missing piece of the big picture of the forces at work on climate.”
The study uses the longest uninterrupted satellite record of aerosols in the lower atmosphere, a unique set of global estimates funded by NASA. Scientists at GISS created the Global Aerosol Climatology Project by extracting a clear aerosol signal from satellite measurements originally designed to observe clouds and weather systems that date back to 1978. The resulting data show large, short-lived spikes in global aerosols caused by major volcanic eruptions in 1982 and 1991, but a gradual decline since about 1990. By 2005, global aerosols had dropped as much as 20 percent from the relatively stable level between 1986 and 1991.
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