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Study Links Smog to Arctic Warming
Reducing ozone pollution improves air quality, eases climate warming


March 17, 2006

NASA scientists have found that a gas involved in summertime smog and global air pollution also plays an important role in warming the Arctic.

In a global assessment of the impact of ozone on climate warming, scientists at the NASA Goddard Institute for Space Studies (GISS) in New York evaluated how ozone in the lowest part of the atmosphere ­ called the troposphere ­ changed temperatures over the past 100 years.

Animation - Click on the arrow to start:
Tropospheric ozone was responsible for one-third to half of the observed warming trend in the Arctic during winter and spring, according to the research at GISS. Ozone is transported from the industrialized countries in the Northern Hemisphere to the Arctic quite efficiently during these seasons. This animation shows anomalous temperature averages from December through May in 1880, 1950, and 1990. The North Polar region remains at normal temperatures (shown in grey) until 1950 when warmer temperatures (shown in red) appear. (844 Kb - no audio). Credit: NASA/Lori Perkins

Most weather occurs in the troposphere. The troposphere begins at the Earth's surface and extends to an altitude of 16-18 kilometers over tropical regions and less than 10 kilometers over the poles.

According to a March 14 NASA press release, the GISS computer model study used best estimates of global emissions of gases that produce ozone to show how much the single air pollutant, also a greenhouse gas, has contributed to warming in specific regions of the world.

The new research says ozone was responsible for one-third to half of the observed warming trend in the Arctic during winter and spring, when ozone is efficiently transported from industrialized countries in the Northern Hemisphere to the Arctic.

The new results identify an unexpected benefit of air pollution control efforts worldwide, said lead author Drew Shindell.

"We now see that reducing ozone pollution can not only improve air quality," he added, "but also have the added benefit of easing climate warming, especially in the Arctic."


Ozone has several roles in the Earth's atmosphere.

In the high-altitude region of the stratosphere, ozone acts to shield the planet from harmful ultraviolet radiation.

In the troposphere, ozone can damage human health, crops and ecosystems. Ozone is also a greenhouse gas and contributes to global warming.

Ozone forms from several chemicals in the atmosphere near the Earth's surface that come from natural sources and human activities, including fossil fuel burning, cement manufacturing, fertilizer application and biomass burning.

The effect of ozone air pollution on climate warming is difficult to pinpoint because, unlike other greenhouse gases such as carbon dioxide, ozone does not last long enough in the lower atmosphere to spread uniformly around the globe. Ozone's warming impact is much more closely tied to the region where it originated.

To capture this complex picture, GISS scientists used a suite of three-dimensional computer models that starts with data on ozone sources and then tracks how ozone chemically evolved and moved around the world over the past century.

The warming effect of low-altitude ozone on the Arctic is very small in summer months because ozone from other parts of the globe does not have time to reach the region before it is destroyed by chemical reactions fueled by sunshine. As a result, when it is summertime in the Northern Hemisphere, ozone-induced warming is largest near sources of ozone emissions.

The computer model showed large summer warming from ozone over western North America and Eastern Europe/Central Asia - areas with high levels of ozone pollution during that time of year.


On the Web:

Full text of the press release and animations


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Ketchikan, Alaska