My biology textbook, after delivering a dire message about chlorofluorocarbons, gave me these two paragraphs about the future of the ozone hole that really only serve to confuse me:
Bolding mine.
Although the quoted text certainly evokes a warm, fuzzy feeling in the hearts of young, liberal-minded, scientific-thinking folk like myself, it also trips my BS meter. Does the Wide World of Science really agree that we’ve done enough (or are on the path of inevitably doing enough eventually) to completely reverse the nearly century-long trend of destroying our ozone layer?
Here’s a good article on the subject. Note the graph at the bottom, displaying CFC levels (at ground level) in the atmosphere.
Nearly everyone has signed the Montreal Protocol (the first one, anyway) so there really is no significant production of CFCs anymore. Since those were the very things causing the problem, it should be clear the problem will eventually go away.
It’s simply not possible for this problem to go away immediately once you stop. All the models so far have been accurate, and the amount already produced won’t be enough to destroy the entire ozone layer. Yes, the time scale is several decades, but it is most likely correct. CFCs at ground level take about 15 years to reach the ozone layer. They live in the atmosphere for 50 years or more (depending on the type). So we can expect that a fair amount will be gone by 65 years after Montreal (1991). The ozone layer will rebuild itself. And skin cancer rates will have their peak about 15 years after the peak in the ozone layer.
At this point, there’s really very little to be done about it. Except for limiting usage of HCFCs, which have similar problems but much shorter atmospheric lifetimes (so will cause little damage to the ozone layer). I don’t know if there’s anything specific concerning HCFCs aside from general guidelines calling for their phase-out in the next half-century.
The earth’s atmosphere is fairly complex, and the only thing you can say with any real certainty is that scientists don’t fully have a handle on it yet. Their models might predict that the hole will go away on its own, but these are models by the same guys who failed to predict the hole’s formation in the first place.
I’m glad that scientists think it will recover, but I can’t say I truly have warm and fuzzies about the whole situation right now.
Sorry, I made several mistakes above. Montreal was 1987, with amendments in 1990 and later. Also, you wouldn’t necessarily add the lifetime of the CFC to the time it takes to reach the atmosphere; 65 years is off. I’ve been ill, and probably shouldn’t have posted when not thinking clearly.
Though it bothers me that people would be suspicious of this model. The chemical reactions are clear. Ozone is replenished constantly – ozone forms from oxygen, which then is broken down by radiation, which can then form ozone again, etc. Chlorine (the element that breaks down ozone into oxygen) is eventually removed by other gases.
Why would you think this won’t happen? Also remember (or if you didn’t know) that the ozone hole over Antarctica only forms in the spring. It’s related to temperature and sunlight; every year the ozone hole ‘repairs itself’. Unless you think the Chlorine will never go away – and really this would only happen if humans keep releasing it – once the Cl is gone, the hole problem is gone as well.
This page runs down the reactions, and shows the data.
A link from that page leads to current data from NASA. Punch in a few dates in spring and summer over the South Pole to see the variations.
I could be wrong but my recollection is that no one ever considered this question until sometime in the 70s and the first people who did made the prediction. When it seemed to be borne out by the date, the world, in a rare outbreak of intelligence actually did something effective about it. So I have little reason to doubt their prediction, which is that by some time late in this century the ozone layer will be back to the status quo ante.
It is interesting to recall that in the 1920s, two physicists invented a sonic refrigerator. It worked and might have taken off and prevented these problems except for the invention of freon which seemed ideal. Oderless, colorless, harmless to people,… The two physicists were motivated by a family in Germany that had perished owing to a leak in their fridge that used ammonia as working fluid. They patented it successfully, since one of them had considerable experience, having been an examiner in the Swiss patent office a couple decades earlier. The other one was Leo Szilard.