Holey Ozone

An interesting feature article in the April 2004 edition of “Environment” journal – “ Abrupt Changes – The Achilles’ Heels of the Earth System” (Steffan, Andreae, Bolin et al). It discusses how it is generally assumed that global change (such as the predicted climate change), occurs as smooth and gradual changes. For example, with climate change, people generally assume that temperatures would gradually increase, but otherwise the Earth System would “continue to operate largely in the state in which it has since the Holocene epoch began (at the end of the last ice age)”. The authors argue against this premise and instead propose that the global environment has in the past shown significant variability (the change in the climate of northern Africa 6,000 years ago being one example). They discuss the possibility that climate change could actually lead to dramatic cooling in the Northern Atlantic region (including both North America and Europe) as a result of an interruption to the Gulf Stream ocean circulation (which helps keep the North Atlantic warmer than it otherwise would be) by the increase in the release of freshwater from melting glaciers and ice sheets.

Anyway, one bit I thought was interesting was the story of how we were in several ways quite lucky in how we were able to deal with the hole in the ozone layer. Firstly, we were rather fortunate that the British Antarctic Survey happened to have a program where they regularly measured ozone concentrations over Antarctica and had been doing this since the 1950s – thus changes to ozone levels over Antarctica were able to be detected quite rapidly. Secondly, it just happened that a group of atmospheric scientists had been conducting studies into the possible impacts upon the stratosphere of the operation of a proposed fleet of supersonic aircraft, and thus were able to apply their knowledge to develop an understanding of how the ozone hole was forming. And the final stroke of good fortune was that the designers of CFCs chose to use chlorine and fluorine rather than bromine. Apparently if they had used bromine, which is at least 30-40 times more reactive with the atmosphere, we would have found ourselves with a lot larger ozone hole a lot faster, before we would have been in a position to deal with it as effectively! Rather fortunate I think.

Of course the other fortunate aspect of the ozone issue was how a global approach to dealing with the problem was able to be quickly developed, agreed and implemented. Something that we have yet to see with climate change.