Warming world would see fewer summer breezes

A group of climate researchers has shown that a warming globe over the next 50 years could result in fewer appearances of summer’s cleansing winds over the Northeast and Midwest United States, resulting in worsening air pollution in the regions.
Loretta J. Mickley, a research associate at the Division of Engineering and Applied Sciences; Daniel J. Jacob, the Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering; B. D. Field of the Division of Engineering and Applied Sciences; and D. Rind of the Goddard Institute for Space Studies in New York examined the impact of increasing greenhouse gas concentrations on pollution events in the United States through 2050.

Mickley and colleagues found that the frequency of cold fronts bringing cool, clear air out of Canada during the summer months declined by about 20 percent. These cold fronts, Mickley said, are responsible for breaking up the hot, stagnant air that builds up regularly in summer, generating high levels of ground level ozone pollution.

“The air just cooks,” Mickley said. “The pollution accumulates, accumulates, accumulates, and finally a cold front comes in, the winds sweep it away.”

Ozone is a highly reactive compound that is beneficial when found high in the atmosphere because it absorbs cancer-causing ultraviolet radiation. Near the ground, however, high concentrations of ozone are considered a pollutant, damaging vegetation and irritating sensitive tissues, particularly lung tissues.

If the model is correct, Mickley said, there would be an increase in difficult days for those affected by ozone pollution, such as people suffering with respiratory illnesses like asthma and those doing physical labor or exercising outdoors.

Mickley and colleagues’ results were reported in the journal Geophysical Research Letters and will be presented at an upcoming conference of the American Association for the Advancement of Science.

Mickley did her crystal ball gazing through a complex computer model developed by the Goddard Institute for Space Studies, with further changes devised by the team at Harvard. It takes known elements such as the number of hours of sunshine per day and the tilt of the earth’s axis, and figures in variables provided by researchers.