Smog Cuts a Global Swath
New glimpses of Earth from space show air pollution wrapping around the planet, spreading haze and hazardous gases across oceans and continents and posing new challenges for cleanup.
The findings, beamed back to Earth from a NASA satellite in orbit for two years, depict in dramatic fashion the global reach of air pollution. Scientists have known for years that man-made pollutants spread far and wide, but this is the first time they have watched it happen from space over a long period.
“Much of the air pollution that humans generate comes from natural sources, such as large fires that travel great distances and affect areas far from the source,” said John Gille, principal investigator at the National Center for Atmospheric Research in Colorado. “With these new observations, you clearly see that air pollution is much more than a local problem. It’s a global issue.”
The findings were presented at a scientific conference in Boston on Wednesday. Researchers from the United States and Canada are participating in the project, one of several ongoing studies of global air pollution.
Emissions Influence World’s Climate
Increasingly, researchers are discovering air pollution is not a transient phenomenon, here today and gone tomorrow. Emissions climb high into the atmosphere, borne on trade winds that circumnavigate the globe.
“We are talking about someone squirting hair spray in the morning in Los Angeles, but by the end of the day it may be reaching someone in South America or beyond,” said UC Irvine chemist Donald Blake, who has collaborated with the researchers on a related study. “It’s a whole new way of thinking global. Everybody is downwind of something.”
Smoke and dust in the sky can dramatically influence climate on Earth. Some pollutants, including soot, nitrates and sulfates from fossil-fuel burning, coat the planet in a fine, aerosol haze. Scientists say too many particles floating around can reflect sunlight, impair crop production in certain places and contribute to cooler temperatures in some places.
Conversely, diesel soot and carbon dioxide are powerful greenhouse gases. They shroud the planet like a blanket, preventing heat from escaping Earth and increasing world temperatures. Those emissions are likely to increase as experts say worldwide fossil fuel consumption is expected to grow by 60% over the next 20 years.
Cleaning up global smog will not be easy. Blame falls on industrial and developing nations alike. Although the United States has some of the world’s most stringent pollution control laws, those controls do not apply abroad. International cooperation, similar to the agreement between Canada and the United States to reduce acid rain emissions, will be required.
Michael Kenny, executive officer for the California Air Resources Board, said one strategy is to seek international standards for vehicles and power plants. He said multinational corporations that manufacture those and other products need to take a leadership role. Environmental groups and other nongovernmental organizations also need to address the matter.
“It means what we have to do is look at this more globally. It’s going to be very difficult. This is going to have to be addressed on a global scale,” Kenny said.
Scientists have long known that air pollutants cover vast distances. Desert dust storms in the Sahara deposit sand in the Caribbean, and Gobi Desert sand has blown to North America. Volcanic ash from the 1980 Mt. St. Helens eruption drifted for hundreds of miles. And the meltdown of the Chernobyl nuclear power plant in the former Soviet Union spread radionuclides all over the world.
But the new findings show how human activity, from forest clearing in the tropics to fuel combustion in the industrialized world, can accumulate into giant plumes of gases that span continents and oceans.
Among the most dramatic findings are immense clouds of carbon monoxide gas blowing across the southern Pacific Ocean from grassland and forest fires in Africa and South America from March to December of last year. The smoke plumes slowly traveled across the Southern Hemisphere more than 6,000 miles to Australia.
In addition, heavy pulses of carbon monoxide, emanating from Asia, Southeast Asia and the Indian subcontinent, stretch across the Pacific, all the way to California and other parts of the North American continent. On the ground, researchers have measured the arrival of intercontinental drift of chemicals from the Olympic Peninsula in Washington state to the Bay Area.
Last year, scientists noticed extensive air pollution generated by forest fires in the American West, although most of the emissions originating in the United States are from fossil-fuel burning for heating and transportation.
Carbon monoxide concentrations reach as much as 150 parts per billion in the air over the Northern Hemisphere, more than double the levels found in the Southern Hemisphere. Humans produce about half the emissions of carbon monoxide, which is a long-lived poisonous gas and an indicator of the presence of other gaseous pollutants.
Pollution Diluted as It Floats From Source
The health consequences for people living far downwind of air pollution are uncertain. The farther pollutants are transported, and the higher they float in the sky, the more diluted they become. Carbon monoxide levels present in smoke plumes over the Northern Hemisphere are well within health-based standards set by the U.S. Environmental Protection Agency. And typically the most unhealthful air pollution occurs near its sources, from motor vehicles to indoor paints and chemicals.
“It’s an open question as to how much it affects air quality in the United States,” said Richard Turco, director of the Institute of the Environment at UCLA. “The pollution would have to be transported downward before it can affect U.S. cities, because the pollutants are usually transported high in the atmosphere.”
With the help of the satellite, which circles the Earth 15 times daily aboard NASA’s Terra spacecraft, scientists are able to see where air pollution originates, how far it spreads and when it is released. That data is critical to developing strategies to predict air pollution and develop countermeasures to protect public health, U.S. Environmental Protection Agency officials said.
“Such information will help us improve our understanding of the linkages between air pollution and global climate change, and it will likely play a pivotal role in the development of international environmental policy,” said atmospheric chemist Daniel Jacob of Harvard University, who participated in the study.
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
Using a satellite, researchers tracked a plume of carbon monoxide, shown in red, traveling across the Pacific Ocean to North America in April-May 2000. The emissions, probably due to forest burning and industrial smoke, originated in Southeast Asia. Global smog is of increasing concern to scientists.
*
Source: NASA
