Some scientific data on the ozone issue

by Wm. Robert Johnston
last updated 26 December 2002

The links below are to graphs (with brief discussion) pertaining to issues involving the ozone layer. For an introduction to the subject see Ozone Depletion.

This basic data is sufficient to demonstrate flaws in the simplistic picture of ozone depletion being presented to the general public as the basis for formulating public policy. Use this data (or any appropriate data) to evaluate my comments below:

The amount of ozone in the atmosphere is affected by a variety of complex factors. It is not the case that ozone amounts will drop if man-made chlorinated chemicals are in the atmosphere. More important factors include: seasonal variations in incident sunlight; seasonal cycles of atmospheric circulation/temperatures; and multi-year trends such as the solar activity cycle. Many factors are poorly addressed by our understanding thus far, including injections of natural chlorine from volcanic eruptions.
The data show that each year ozone amounts can increase 10% or more. While this is mostly due to large scale movements of ozone within the atmosphere, global averages show that large amounts of ozone can be created in the short term (over a few months).
The seasonal variations of 10-20%, multi-year variations of 5%, and site-to-site variations of 15% undermine the assertion that a possible 5% decrease in 30 years is a cause for panic.
Some sources have claimed that increases in measured ozone since 1992 show that the international ban on CFCs has reversed destruction of ozone. This is clearly incompatible with the ozone depletion model that was used to force the policy change. If the model was correct, since the amount of chlorine from man-made chemicals is virtually unchanged, then the rate of destruction should not be changed.
Even if a 5% decrease is caused by humans, available evidence is inadequate to support the claim that the benefits of the CFC ban outweigh the costs. These costs are not merely financial, they are human: the CFC ban will put some health care out of the reach of poor people around the world, causing disease and death.