Emergency repair for the ozone hole?

The year is 2007. The ozone hole over Antarctica has expanded each year and has now become a severe global threat. Sometime in July, several hundred large airplanes head out on a dangerous mission over the sunless Antarctic continent. Their goal: to spray 50,000 tons of ethane into the stratosphere in an attempt to stop the ozone hole from forming as the austral spring approaches.

Though it may sound like the plot for a new Arnold Schwarzenegger movie, this idea has been raised by a team of atmospheric scientists who use computer models to explore mthods of stemming the annual ozone depletion over Antartica.

Ralph J. Cicerone of the University of California, Irvine, who helped originate the idea, calls it "a concept, not a proposal." While he and his colleagues want scientists to consider the approach, they do not expect anyone to actually try it, he says. "We understand as much as anybody that there could be very unexpected problems arising if you introduced yet another chemical into the system."

Their modeling results, reported in the Nov. 22 SCIENCE, suggest that a sufficient amount of ethane or propane added to the Antarctic stratosphere each year could chemically halt much of the ozone destruction caused by chlorine pollution there. In theory, hydrocarbons could limit ozone loss by binding with free chlorine molecules, preventing these molecules from attacking ozone. But the researchers warn that scientists still don't know enough about the atmosphere to determine whether the strategy could work.

Although most nations have agreed to end production of many ozone-destroying chemicals, scientists have warned that the Antarctic ozone hole could recur annually for the next 100 years as the atmosphere slowly cleans itself of existing chlorine pollution. Some projections sugges that the Antarctic situation could worsen before it improves. That concerns scientists because the severe depletions over Antarctica each spring may contribute to the ongoing erosion of the global ozone layer.

Daniel Lashof of the Natural Resources Defense Council in Washington, D.C., says the threat of even greater Antarctic ozone loss in the future makes it worthwhile to explore ideas such as those raised by Cicerone's team. "The situation is so critical that if things really continue to get worse, you may want to have these kinds of emergency measures available," Lashof says.