The effects of these depletions on the global ozone budget and the possibility of similar massive ozone reductions occurring over the Arctic are of prime interest.

An accelerated loss of NO 2 through aerosol chemistry is therefore likely to increase the rate of ozone reduction in autumn, but have little effect in spring when ozone losses will be dominated by heterogeneous reactions on polar stratospheric clouds in the lower stratosphere.

But fearful of provoking public outcry, E.P.A. is reluctant to mandate major ozone reductions.

"Year-to-year fluctuations in the geographical size of the ozone hole and the timing of the ozone reduction are believed to be related to meteorological factors such as temperature and winds, rather than further increases in ozone-destroying chemicals in the atmosphere," Hofmann said.

The relative lack of upper level ozone in New Zealand agrees with other global ozone observations suggesting that ozone reductions have extended beyond the poles to include the midlatitudes in both the Northern and Southern Hemispheres.

He predicted that methanol cars could bring an ozone reduction of 25 to 40 percent for most cities.

The ozone reduction would expose Arctic wildlife to more ultraviolet radiation and might mean transient increased exposures for people elsewhere in the Northern Hemisphere, he said.

If measuring increased crops by total metric tonnage gains, China, India, and the US would benefit the most here, but the Middle East would see the greatest improvement by percentage (due to large potential ozone reductions).