THE hue-and-cry over damage to Earth's protective ozone layer has led to a "capture."
Scientists from the US National Oceanic and Atmospheric Administration (NOAA) have recorded a marked drop at ground level in the rate of increase for two man-made chemicals that significantly contribute to ozone's destruction. The researchers conclude that similar declines should appear in about four years where it is most needed, in the stratosphere. There, the fragile layer of ozone shields Earth from excessive levels of the sun's ultraviolet radiation.
If this positive trend continues, it would mark a success for the 1987 Montreal Protocols and its subsequent provisions. The agreements initially banned production of chloroflourocarbons (CFCs) by the year 2000. But with each new report of ozone "holes," first at Earth's poles and later at more temperate latitutdes, public pressure grew. Last year, the ban was advanced to the end of 1995.
Since 1977, the NOAA researchers tracked ozone levels weekly. Last year, when they analyzed their data, they were puzzled by a drop in the rate of increase after 1988. The test equipment checked out, so the researchers called E.I. du Pont de Nemours & Co., whose scientists had tracked a similar decline in the amount of CFCs produced worldwide. If current trends hold, the NOAA scientists expect abnormal concentrations of chlorine, the component of CFCs that breaks down ozone, to peak by the year 2000. Ozo ne levels would fall to more typical levels 50 to 100 years later.
To help ensure this, industrial countries must assist developing nations to avoid the use of CFCs, largely found in refrigeration equipment. Nations such as China and India have been given 10 years beyond the protocols' deadline to comply, yet CFC alternatives are relatively expensive. The protocols provide for a fund to help developing countries offset the cost of substitutes; it deserves consistent support.
The phenomenon of ozone depletion will not disappear. When Mt. Pinatubo erupted in 1992 in the Philippines, researchers recorded a brief but sharp ozone loss traced to the volcanic gases emitted.
Much about the atmosphere remains unknown. The NOAA results should not be allowed to undercut additional research into ozone depletion. A deeper understanding of atmospheric chemistry and processes would further separate natural factors from man-made, and, in turn, help evolve better policies for reversing damage.