A Georgia State University researcher says the Clean Air Act signed by President Richard Nixon in 1970 led to climate change - in a good way. 

Jeremy Diem, an associate professor in the Department of Geosciences, analyzed summer rainfall data from nine weather stations in the Atlanta metropolitan area from 1948 to 2009, and discovered that precipitation increased in the late 1970s after drops in the 1950s and '60s.

Cause: Passage of the Clean Air Act of 1970, he says. Pollution had been higher in the earlier decades. Some studies have found a general correlation between air pollution and rainfall, with higher concentrations of particulates in the air suppressing rainfall, they conclude.

Diem says he has shown for the first time that a substantial decrease in pollution in a specific metropolitan area caused an increase in rainfall. He says the findings are likely to apply to other urban areas across the United States that saw similar pollution decreases. 

"Really, the only plausible reason for this increased rainfall is the reduced pollution due to the passage of the Clean Air Act," Diem said. "This probably happened in many cities other than Atlanta."

The study may also have implications for other urban areas around the world that may be experiencing drop-offs in rainfall due to pollution, Diem said.