Image: Chart shows chemical equator
Glenn Carver  /  Cambridge University
This chart shows a 'chemical equator' just north of Australia. Red represents high levels of carbon monoxide on Jan. 30, 2006. Blue reflects clean air. staff and news service reports
updated 9/23/2008 11:50:19 AM ET 2008-09-23T15:50:19

Scientists have discovered a "chemical equator" that divides the polluted air of the Northern Hemisphere from the largely uncontaminated atmosphere of the Southern Hemisphere.

Researchers found evidence for an atmospheric chemical line about 30 miles wide in cloudless skies in the Western Pacific, with levels of carbon monoxide four times higher on the northern side.

The discovery will provide clues to help scientists model simulations of the movement of pollutants in the atmosphere more accurately, and to assess the impact of pollution on climate, the researchers said in a statement on Tuesday.

Previously, scientists believed that a cloudy Pacific region where the trade winds meet formed the boundary between the polluted air of the Northern Hemisphere and the clearer air of the Southern Hemisphere.

"The shallow waters of the Western Pacific, known as the Tropical Warm Pool, have some of highest sea surface temperatures in the world, which result in the region's weather being dominated by storm systems," noted Jacqueline Hamilton, a University of York researcher and lead author of a report to be published in the Journal of Geophysical Research — Atmospheres, a publication of the American Geophysical Union.

"The position of the chemical equator was to the south of this stormy region," she said, adding that "powerful storms may act as pumps, lifting highly polluted air from the surface to high in the atmosphere where pollutants will remain longer and may have a global influence."

The scientists discovered evidence of the chemical equator using sensors on a specially equipped airplane during flights north of Darwin, Australia.

Reuters contributed to this report.


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