An international consortium of researchers from three different projects are investigating one of the world’s most potent sources of air pollution: the so-called “Asian Express,” created over the last decade by rapid Asian industrialization, which is driving changes in the Earth’s atmosphere.
A series of recent studies tracked the brown pollution cloud along its annual transpacific migration. Each spring, strong winds blow east from Central China, gathering dust which acts like a sponge, soaking up pollution from East Asia’s thick blanket of smog.
This image, produced from satellite data, shows the Asian dust cloud moving over the Yellow Sea on April 11, 2001. The cloud is colored gold.
Traveling Particulate Stew
This dirty particulate stew most directly threatens Japan, Korea and Taiwan. But this brown cloud can blow eastward across 6,000 miles of ocean to the United States in only four to 10 days—too little time for the air to be cleansed over the sea.
Given the pass-along nature of pollution, however, researchers point out that every region of the world makes its contribution.
“The amount of pollution we get from Asia is probably not dramatically different from what we send to Europe, and Europe sends to Asia,” says Barry Joe Huebert, an atmospheric chemist at the University of Hawaii in Honolulu. “We have to think of atmosphere chemistry and its impact on air quality and climate as global issues.”
Huebert and other authorities on wind borne pollution presented their findings in December at the annual meeting of American Geophysical Union. Their research identified the major sources of pollution and quantified how much reaches North America.
“The ultimate use of this data will be for setting policy for the use of fossil fuels and other pollutants we put into the atmosphere,” said Huebert.
During spring 2001 and 2002, hundreds of scientists from 13 countries joined forces to study air pollution from Asia. The international team tracked and sampled dust plumes from ground stations, aircraft, ships and by satellite.
Atmospheric Aerosols
Huebert headed the research team for the Aerosol Characterization Experiments, or ACE-Asia, which concentrated on aerosols—tiny solid or liquid particles suspended in the atmosphere. Some aerosols come from natural sources like dust from volcanoes and deserts. But most come from human activities like burning wood and coal. Asia is one of the largest sources of aerosols on the Earth.
Aerosols can harm human health by causing asthma and through exposure to the carcinogens they harbor, including arsenic, lead, chromium, selenium and other toxic materials.
Aerosols powerfully affect the environment and climate. They absorb the acids that create acid rain. They reflect sunlight and influence rainfall patterns, affecting weather and global climate change. Understanding the way they affect climate is one of the more perplexing problems for atmospheric scientists.
Atmospheric scientists are puzzling over the interaction of aerosols and other factors like greenhouse gases—carbon dioxide and other gases that trap the sun’s heat and warm the Earth’s atmosphere.
Altering Climate
“While many parts of Earth are warming up because of greenhouse gases, in places where there are huge concentrations of aerosols, there is actually cooling,” said Huebert. In April, for example, the surface cooling effect of aerosols downwind of Asia is 10 percent higher than warming caused by greenhouse gases, Huebert notes.