Good News for the Ozone?

“Hints of ozone recovery spotted
Satellites pick up early signs that CFC ban is working.
30 July 2003
HELEN PEARSON


The Antarctic ozone hole has not begun to close yet.
© ESA



It may be the beginning of an environmental happy ending. Scientists say they have the first clear evidence of a slowdown in the ozone layer's decline.

This has been hoped for since the Montreal Protocol was signed in 1987. The international treaty banned the use of chlorine-containing aerosol propellants and refrigerants such as chlorofluorocarbons (CFCs). These demolish the planet's ultraviolet sunscreen, ozone.

The rate of ozone destruction 35-45 km above the Earth has roughly halved since the 1980s to around 3-5% per decade, Michael Newchurch, of the University of Alabama at Huntsville, and his colleagues have now found1. The rise of ozone-destroying chlorine levels has also begun to brake.

The team analysed more than 20 years of data from the SAGE I, SAGE II and HALOE satellites. These estimate the amount of ozone in the upper stratosphere by measuring the levels of ultraviolet light that it absorbs.

"It is the first sign that what we've been advocating is beginning to work," says stratosphere expert Lon Hood of the University of Arizona, Tucson. Other studies hinted that chlorine levels were falling, but this is the first to show that they are having an influence on ozone.

Researchers are not popping corks yet. It may take a decade or more before ozone levels begin to recover. There is also little sign that the larger store of ozone in the lower stratosphere is recovering - or that the ozone hole, which yawns over the Antarctic every spring, is beginning to close.

Global warming might also interfere with ozone mending, for example by altering the way that air mixes in the lower stratosphere, says Rich Stolarski, who studies ozone depletion at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "I'm convinced there'll be surprises in the way it recovers," he adds.

Setting an example

Although this week's results are preliminary, researchers point to the steadying ozone layer as an environmental success story. If scientists and policy-makers hadn't acted, "there would be many hundreds of times more skin cancer", says Newchurch.

Chemists first recognized in the 1970s that CFCs might break down to release ozone-destroying chlorine. The Montreal Protocol demanded that such compounds be phased out during the 1990s and beyond.

We have to maintain the restrictions for the rest of our time on
the planet
Michael Newchurch
University of Alabama



It is important that success does not turn into complacency, say researchers, and that bans on CFCs are not relaxed. "We have to maintain the restrictions for the rest of our time on the planet," says Newchurch.

They also acknowledge that global warming will not be such a straightforward problem to solve - there are thought to be many more factors influencing levels of greenhouse gases than ozone. "It's not something that can be turned around in a decade," says Hood.


References
Newchurch, M.J., Yang, E-S., Cunnold, D.M., Reinsel, G.C. & Zawodny, J.M. Evidence for slowdown in stratospheric ozone loss: first stage of ozone recovery. Journal of Geophysical Research Atmospheres, published online, doi:10.1029/2003JD003471 (2003). |Article|


© Nature News Service / Macmillan Magazines Ltd 2003”

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What about the destruction of the Earth?
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What about the fact that the Earth will clean the human virus off itself it needs to and start over again?”

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