Using a computer model of the atmosphere that incorporates physical and chemical environmental processes, Stanford University Professor Mark Jacobson found that for each increase of one degree Celsius caused by carbon dioxide, the resulting air pollution would lead to about a thousand additional deaths and many more cases of respiratory illness and asthma in the United States.

The study, accepted for publication in Geophysical Research Letters, found that more than 20,000 air-pollution-related deaths per year per degree Celsius may be due to this greenhouse gas.

"This is a cause and effect relationship, not just a correlation," Jacobson said Thursday in a release. "The study is the first specifically to isolate carbon dioxide's effect from that of other global-warming agents and to find quantitatively that chemical and meteorological changes due to carbon dioxide itself increase mortality due to increased ozone, particles and carcinogens in the air."

The U.S. Environmental Protection Agency recently ruled against states setting specific emission standards for carbon dioxide based in part on the lack of data showing the link between carbon dioxide emissions and their health effects.