The atmosphere may be losing a crucial chemical that scrubs the air of methane and other gases that may be warming the planet, according to a preliminary study by Los Alamos National Laboratory researchers.

The depleted atmospheric scavenger is called a hydroxyl radical. It consists of an oxygen and a hydrogen atom and is called OH for short. It breaks down methane, converting it to water and ethane, a less persistent greenhouse gas.

Jim Kao and colleagues report the amount of OH in the Northern Hemisphere is one-third the amount found over the Southern Hemisphere.

Kao contends this "serious depletion" of OH is caused by the fact that more and more methane and other hydrocarbons are being pumped into the atmosphere. This overdosing of methane is using up the available OH. Atmospheric methane is increasing about 1 percent per year. If the depletion continues, Kao suggests, more methane may remain in the atmosphere longer, magnifying potential global warming.

However, Kao and Ralph Cicerone of the University of California at Irvine caution that their estimates of OH concentration are not based upon direct measurements, but rather an interplay of computer simulations and measurements of another chemical, methylchloroform, which is easier to measure and whose amount is related to that of OH. "It's all still very preliminary," Cicerone warned.