ROCHESTER, N.Y., Sept. 18 (UPI) -- A study of air trapped in Greenland's snowpack indicates atmospheric levels of carbon monoxide in the 1950s were higher than now, a U.S. researcher said.
Researcher Vasilii Petrenko, an assistant professor of Earth and environmental sciences at the University of Rochester in New York, concluded CO levels rose slightly from 1950 until the 1970s, then dropped to present-day values.