Refrigerants for the 21st Century
10. Evidence of Ozone Layer Damage

The size of the springtime "hole" in the Antarctic O3 layer had continued to grow, peaking in the early 1990's when it covered nearly the entire continent. Average ozone concentrations dropped remarkably. Studies were extended to the region above the Arctic Circle at that time. Here too O3 loss is seen, though not as extensive as over the Antarctic. Careful study of accumulated data from satellites orbiting the earth and from ground-based instruments also show a worldwide decline in stratospheric O3 since the mid-1970's, especially during wintertime. The O3 losses exceed what would be expected from the variability owing to natural phenomena.

Stratospheric Ozone in the Antarctic Courtesy Center for Atmospheric Science, University of Cambridge

The growing evidence for stratospheric O3 damage prompted an almost unprecedented response from the nations of the world. Meeting in Montreal, Canada in September, 1987, representatives of 24 nations agreed upon a protocol limiting the use of and freezing, then cutting the production of CFC's and halons. Here was true international cooperation in advance of a catastrophe! And even before the cause(s) was clearly established. In addition to this foresight, the negotiators agreed to examine new data periodically and adjust the Protocol as needed. This has led to subsequent meetings in London, Copenhagen and Cairo where timetables have been shortened and the scope of regulations has been expanded to include HCFC's (still contain Cl), and chlorocarbons such as CCl4 and methyl chloroform (CH3CCl3). Even methyl bromide (CH3Br), an important crop fumigant, is under scrutiny. Though not yet approved by all the Montreal Protocol signatories, the current worldwide production phase-out goal for CFC's and HCFC's is 2004. The timing is even shorter for the halons - 2000.

One of the issues addressed by the Montreal negotiators was how not to impose a hardship on developing countries. As a result, longer timetables have been given to them. It is peculiar that the giant nations, such as China, Russia and India which potentially are the world's largest CFC's users, benefit by being considered to be "developing" nations.

The scientific answer as to why the stratospheric O3 problem is most noticeable in the polar regions was finally found when it was shown that ice particles in clouds in these very cold regions trap pollutants, such as CFC's and halons. They remain relatively inactive until springtime solar radiation strikes the particles, causing the formation of O3-damaging Cl and Br radicals. The Antarctic problem is accentuated by the lower wintertime temperatures there and the peculiar meteorological conditions which isolate the ice-filled clouds from the surrounding continents of Africa and South America. There is more natural movement of the ice clouds over the Arctic.

Careful analytical analyses of the stratosphere have now confirmed the presence of compounds related to CFC's, namely, HF and carbonyl fluoride (COF2).   There are no natural sources of F compounds to escape to the atmoshpere. In addition, all of the larger production fluorocarbons - CFC-11/-12/-113 and HCFC-22 - are routinely measurable in the troposphere.

The need for alternatives to CFC's, so important to our way of life, had become apparent. Developed countries had agreed to stop their production by 1996. Assuming the current worldwide phase-out goals and that all countries adhere to them, the predicted maximum stratospheric O3 loss is expected in 2000.