Just ran across a story at NASA, Good News and a Puzzle, about evidence that the Earth's ozone layer appears to be "healing," except for the ozone hole over Antarctica, which is bigger than ever.

The question is why? Is the Montreal Protocol responsible? Or is some other process at work?

It's a complicated question. CFCs are not the only things that can influence the ozone layer; sunspots, volcanoes and weather also play a role. Ultraviolet rays from sunspots boost the ozone layer, while sulfurous gases emitted by some volcanoes can weaken it. Cold air in the stratosphere can either weaken or boost the ozone layer, depending on altitude and latitude. These processes and others are laid out in a review just published in the May 4th issue of Nature: "The search for signs of recovery of the ozone layer" by Elizabeth Westhead and Signe Andersen.

The Nature article's abstract suggests that, "whatever the benefits of the Montreal agreement, recovery of ozone is likely to occur in a different atmospheric environment, with changes expected in atmospheric transport, temperature and important trace gases. It is therefore unlikely that ozone will stabilize at levels observed before 1980, when a decline in ozone concentrations was first observed."

The Montreal Protocol and other policies to reduce or eliminate CFCs in the environment had opposition from industries that were affected by CFC restrictions, an opposition that reminds me of current debate about global warming. In both cases you can point to complex sources of potentially catastrophic environmental change, with business interests tending to dismiss the need for changes that might affect their bottom line. It would be relevant to prove beyond a doubt that changed behavior, away from production and use of CFC, has resulted in at least partial healing of the ozone layer. However it's extremely likely if not 100% clear that substantially reducing CFC emissions has had a positive effect.

And while there may be a complex set of causes responsible for both ozone depletion and global warming, we puny humans should continue to fix those factors – behaviors – that are within our control. (And don't forget the "debate is over" design competition!)

It's good to read an article about the ozone layer that states that there are also natural occurences that cause depletion of same.

I worked in Antarctica during 1989 at Casey station and when people ask me about Antarctica they imagine you can really feel the difference with each time you go outside it must be like being zapped in a microwave. hahaha
Sandy

Posted by: Sandy J Cave on May 29, 2006 6:13 PM

If you follow the NRDC link in my post re. CFCs, you'll see that they were widely adopted because previous refrigerants were toxic. There's all sorts of tradeoffs and unintended consequences associated with human activity and escalating standard of living in industrial and postindustrial countries.

Of the complex factors driving ozone depletion, global warming, and other troubling environmental trends, the factors we can realistically address are those associated with human activity. But that shouldn't mean we overlook other drivers.

Posted by: Jon Lebkowsky on May 29, 2006 6:42 PM

Some of the same people who refused to see human behavior in the ozone hole still refuse to see human behavior in greenhouse gases. Newton, Einstein, and even Murphy has been repealed for them.

There are way too many knee-jerk anti-enviros.

Posted by: gmoke on May 29, 2006 7:52 PM

They'd be easier to ignore if they weren't making policy.

Posted by: Jon Lebkowsky on May 29, 2006 8:18 PM