Boston — The Montreal protocol to stop depletion of the earth's protective ozone layer may be outdated even before it takes effect next year. Environmental Protection Agency director Lee Thomas said so in September. A group of scientists at a UN environmental conference in The Hague said so Tuesday. They now want tougher measures.
The 1987 UN protocol calls for a 50 percent reduction in ozone-depleting chloroflourocarbons (CFCs) by 1998. This sounded like a healthy chunk of the problem until studies earlier this year revealed that the ozone layer is thinning faster than previously predicted.
When CFCs break down, they release chlorine that destroys ozone molecules in the stratosphere. This is not to be confused with tropospheric ozone formed by pollutants close to the earth. Since the stratosphere (upper atmosphere) and troposphere (lower atmosphere) do not mix, the abundance of ozone pollution in the air we breathe does not compensate for losses of ozone that blocks ultraviolet (UV) radiation in the upper atmoshphere.
Trends show that the ozone in some regions of the Northern Hemisphere decreases in winter months by several percentage points. Antarctic ozone has been known to decrease by 60 percent.
Ironically, Antarctic ozone is less depleted this year than in years past, according to the National Aeronautics and Space Administration and the National Oceanic and Atmospheric Administration.
Scientists attribute the improvement to warmer temperatures that reduce the number of ice particles in stratospheric clouds. These particles provide a surface for chemical reactions that damage ozone.
This year's observations confirm earlier predictions, says John E. Frederick, a professor of atmospheric science at the University of Chicago.
``It means we understand it somewhat. It doesn't mean we should relax. Next year the ozone hole should be back as big as ever, if not bigger,'' he says.
``In the 1987 ozone hole the ultraviolet radiation levels were way above what simple creatures down there had ever seen before,'' Dr. Frederick says. While one-celled creatures might have negative responses, the levels are not likely to harm humans.
``During one of these very very severe ozone holes, the UV radiation over Antarctica gets up to levels comparable to what you might get in Boston in spring or summer,'' he says.
The real worry is that ozone in the middle latitudes will be damaged, he says.
``If an ozone hole were to develop over mid-latitudes, that would be a real disaster, because we would be talking about a gigantic increase in UV radiation,'' Frederick says. He says he thinks this scenario is possible, but unlikely.