Scattered across sky like a film of dust over a window, vast quantities of tiny black soot and other industrial particulates from Southeast Asia have been spreading across the North Pacific each spring, becoming a major driver in climate change along the U.S. West Coast and Arctic.
Measurements from 2001 and 2004 show
springtime transport of black carbon
across the Pacific Ocean in spring.
Fang Li, Scripps Institution of Oceanography
More than 75 percent of the tiny bits and aerosol particles carried at high altitudes over western North America during spring comes from Asian industry and traffic, according to new research by Professor V. Ramanathan and his team at Scripps Institution of Oceanography in San Diego.
They found that the soot had a surprising impact — heating the sky over the Pacific Ocean much more than expected, perhaps has much as 40 percent of the forcing blamed on carbon dioxide over the past century.
“It was a major surprise,” said Ramanathan in a release. “When we came up with the preliminary results, we had to check it and recheck it.”
These aerosol particles get created by incomplete combustion — think of the harsh smoke that billows off a campfire. Agriculture, automobile exhaust and forest fires all contribute to the haze.
As it spreads across the Earth and drifts north, this “black carbon” can absorb solar radiation to heat upper layers of the atmosphere while blocking sunlight from reaching the ground. Aerosols and soot from Russia and Europe are now thought to be major pollutants in the Arctic, with the potential to speed up the melting of snow and ice.
A release from Scripps explains further:
Though the transported black carbon, most of which is soot, is an extremely small component of air pollution at land surface levels, the phenomenon has a significant heating effect on the atmosphere at altitudes above two kilometers (6,562 feet).
As the soot heats the atmosphere, however, it also dims the surface of the ocean by absorbing solar radiation, said Ramanathan, a climate scientist at Scripps, and Odelle Hadley, a graduate student at the Center for Atmospheric Sciences at Scripps. The two are lead authors of a research paper appearing in the March 14 issue of the Journal of Geophysical Research.
The dual effect carries consequences for the Pacific Ocean region that drives much of Earth’s climate.
“That’s the primary concern we have with these aerosols,” said Hadley. “They can really affect global climate.”
“The soot heating of the atmosphere exceeds the surface dimming and as a result the long range transported soot amplifies the global warming due to increase in carbon dioxide,” said Ramanathan. “We have to find out if this amplification is just restricted to spring time or is happening throughout the year.”
A special aircraft documented trans-Pacific
black carbon transport at high altitudes.
Credit: Department of Atmospheric Science
University of Wyoming
The Scripps researchers compared data taken from a specially equipped aircraft in 2004 with measurements by 30 West Coast meteorological stations, then worked it over with a computer predictions. Hadley is working on a study of how black carbin influences snow.