Ozone Depletion and Global Warming Linked—Again

The latest government press conference on the ozone layer, held on April 5th, announced that this protective shield had been eroded over the Arctic region last winter. After conducting research over the past several months, a coalition of European agencies and NASA concluded, among other things, that the Arctic ozone layer was depleted by as much as 60 percent.

As with past efforts to garner media attention for ozone research, the press conference was very selective and misleading. For example, the 60 percent depletion only occurred at a particular altitude, above and below which the ozone layer was not affected. And most importantly, the bottom line effect on ground-level ultraviolet B radiation (UVB) from ozone loss remains so small that scientists still cannot even say that there has been a long-term increase at all.

The press conference was much like any of a dozen others over the years, but with one relatively new wrinkle. Several participants blamed the putatively worsening ozone problem on global warming. Scientist Georgios Amanatidis explained that "warm air is being trapped at lower levels by greenhouse gases and therefore the upper atmosphere is much colder, which helps trigger the chemical reaction that destroys ozone." Crossing the line from science to advocacy, Amanatidis concluded that this new research "certainly puts even more emphasis than ever on the need to reduce greenhouse gases as outlined in the Kyoto Protocol."

This is not the first time the two major global environmental issues were linked in order to sell a policy prescription as a means of killing two birds with one stone. Back in the mid-1970s, when the ozone depletion hypothesis was still new, several scientists insisted that chloro- fluorocarbons (CFCs), the class of refrigerants believed to be the main ozone depleters, were global warming gases as well. Indeed, one 1976 study predicted that CFCs, if unregulated, would overtake carbon dioxide as the primary anthropogenic greenhouse gas by 2000. CFCs’ green- house potential was frequently offered up as a second good reason to ban these compounds, in addition to the main concerns about ozone loss.

But then the policy considerations changed, and, strangely enough, so did the science. By 1987, the Montreal Protocol was signed, committing the US and other developed nations to CFC reductions based entirely on their ozone depletion potential. By the early 1990s, this treaty was strengthened into a complete ban on CFCs. At this point, there no longer was anything to be gained by demonizing these compounds as greenhouse gases. Quite the contrary, the Bush Administration, which was opposed to carbon dioxide emissions reductions, hoped to get credit in a greenhouse context for the CFC reductions the US was already committed to under the Montreal Protocol. Unwilling to give the US this free ride, a number of scientists changed their minds and decided that CFCs were not global warming gases after all. Their reason: Since CFCs deplete the ozone layer, and ozone depletion has an offsetting cooling effect, the net greenhouse potential is a wash. From that point on, the already-banned CFCs have stayed off the table in all global warming discussions.

The science (more accurately, the spin put on the science) may have done a flip-flop, but it consistently supported additional international restrictions on industrial activities.

Now we are to believe that the as-yet-unratified Kyoto Protocol will save us from the twin threats of global warming and ozone depletion. Granted, the hypothesis that there may be a link between greenhouse gas-induced stratospheric cooling and increased ozone loss is plausible enough to warrant further research. But if the past is any guide, international environmental agreements marketed as two-for-one deals may not be as good a bargain as they sound.

Ben Lieberman (blieberman@ cei.org) is a CEI policy analyst.