The Why Files The Why Files --

The fact of global warming

POSTED 24 FEB 2005
What's warming got to do with me?
 City on the horizon covered by brown haze. Climate scientists agree that the rapid warming predicted 25 years ago has begun to melt glaciers, move species, raise sea level and feed forest fires and perhaps storms. But if these problems seem too abstract, consider this: If you live in the polluted Midwest or Northeast, global warming may interfere with your breathing.

Airborne particles, the main ingredient of haze, smoke, and dust, present serious air quality problems in many areas of the United States. Could global warming make for more pollution over big cities?Particle pollution can cause serious health problems, even at concentrations found in many major cities, like Boston, shown above. Photo: EPA

Loretta Mickley, a research associate in the division of engineering and applied sciences at Harvard University, used a computer model to predict how global warming would affect the intense blankets of pollution that plague parts of the United States every summer. During these episodes, hot air gets trapped near the ground, and the sun cooks pollution from cars and industries, making the chemically reactive compound ozone.

Much higher in the atmosphere, ozone is a good thing: it blocks harmful ultraviolet radiation from the sun. But when you breathe it, ozone "can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma... and reduce lung function and inflame the linings of the lungs. Repeated exposure may permanently scar lung tissue," says the EPA.

Blocks show areas of study across US mapPollution episodes could rise in the Midwest and Northeast after global warming. Courtesy Loretta Mickley

Shall we study?
Mickley says her studies grew from the observation that "day-to-day meteorology affects pollution." In the average year, for example, New England has five periods when ozone exceeds EPA health standards. But in 1988, the region's hottest-ever summer, it had 19 episodes.

Typically, the pollution episodes end when cold fronts arrive from Canada, but the computer model showed that by 2050, "fewer cold fronts would come and blow away the pollution," Mickley said. "They will still arrive, but less often."

In the Midwest, pollution episodes would last 30 percent to 100 percent longer than now. "The atmosphere," Mickley said, "becomes more sluggish, with fewer of these low-pressure systems coming through."

Persistence of pollution episodes in the Midwest
Pollution lasts 30 to 100% longer in Midwest.
Original graph courtesy Loretta Mickley

The worst is yet to come?
About 125 million people now live in the two regions where the pollution could intensify, the Midwest and Northeast. Residents of metropolitan areas -- about 60 million people today -- would suffer worst from the extended exposure to pollution, Mickley says.

That's bad enough, but the study may understate the true danger, Mickley indicates, since it did not calculate the formation of ozone, which would likely increase along with temperature. "There may be more when we do a full-chemical simulation; we expect to see reduced cloud cover, more high-temperature days, the sun beating down, and that means more ozone formation, and higher pollution levels."

Have a hot time in the ol' bibliography tonite!

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