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October 1, 2007
All Sorts of Holes
Posted by Derek
One of the things I like most about science is how thoroughly you can be taken by surprise. A good check on a field’s vigor is whether or not its practitioners are being ambushed by new data. By that standard, what at first looks like an embarrassment for the ozone-hole chemists actually makes them look pretty good.
The chemistry of ozone depletion over the Antarctic is well understood. Or is it? One of the key molecules in the process is chlorine peroxide (also known as chlorine monoxide dimer). It’s understood to be split by sunlight into reactive free chlorine radicals, which go on to catalyze the conversion of ozone into plain oxygen. In the process, the peroxide forms again, and the whole cycle starts over. While this is by no means the only means by which chlorine depletes ozone, it’s long been thought to be the main one.
But chlorine peroxide is a difficult molecule to work with. Extremely unstable by sea-level laboratory standards, it’s been hard to isolate in pure form for study. And despite the generally accepted cascade of ozone depletion reactions, it hadn’t even been detected in the Antarctic until 2004, which difficulty had been largely chalked up to its short lifetime. Now, though, a team at JPL has produced the best synthetic samples of chlorine peroxide to date, and they’ve checked how quickly it decomposes in the presence of ultraviolet light. And, well. . .the problem is, the stuff falls apart much more slowly than anyone had predicted – many, many times more slowly. If they’re right, it’s hard to see how the accepted chemistry of chlorine peroxide-driven ozone depletion can be correct.
This has produced all sorts of surprised reactions in the atmospheric chemistry world, summed up here at Nature News. Everyone is taking this report seriously, as well they should, and a number of explanations are already being tentatively advanced. All of them are going to require a lot of revision of what we thought we knew, though. (I should note that the depletion of ozone itself isn’t in question; that’s an experimental fact. Just how it’s being lost is the problem). Nature quotes researcher Marcus Rex:
"Overwhelming evidence still suggests that anthropogenic emissions of CFCs and halons are the reason for the ozone loss. But we would be on much firmer ground if we could write down the correct chemical reactions."
I have little doubt that this will get figured out eventually. The reason I’m optimistic is that this area of research is going along the way it’s supposed to. People are spending the time and effort to check assumptions, and when something turns up unexpectedly, the results are published in a good journal for everyone to see and argue over. That will lead to another round of theorizing, then more rounds of experimentation as people try to prove the latest ideas right or wrong. And thus we close in on the truth. That’s exactly, exactly how it should work.
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1. milkshake on October 2, 2007 2:55 AM writes...
On a similar subject: Alarming global warming model predictions of antropogenic effects are based on less solid ground - and the sceptics that dare to question the validity of key asumptions get acused of agenda (if not of an outright corruption)
Enviromentalism unfortunately degenerated to a political science.
Permalink to Comment2. John Spevacek on October 2, 2007 8:39 AM writes...
"I should note that the depletion of ozone itself isn’t in question; that’s an experimental fact. Just how it’s being lost is the problem." But knowing the "how" is critical to understanding the "cause" and the "cure". Are we (21st century society) to blame? Why? What should/could we do differently? Are our earlier "fixes" even fixes at all?
Permalink to Comment3. tom bartlett on October 2, 2007 8:40 AM writes...
"Alarming global warming model predictions of antropogenic effects are based on less solid ground"
Not only is climate change real; I'd say it is the number one, top problem facing the world. Even if the extensive warming turns out to be natural, it will still have a huge impact on how we live; the last time ice caps melted was, like, 60 million years ago, and there were a lot fewer than 7 billion people trying to eke out a living on Earth back then.
Permalink to Comment4. Curious Wavefunction on October 2, 2007 3:03 PM writes...
Also, scientists usually weigh the consequences and effects of climate change within a window of probabilities. The alarming scenarios usually cited by critics are at the upper end of the scale and have relatively low probability. The "middle" scenarios which have high probability are quite serious themselves. Some might call *them* alarming. But I agree that to bin someone criticising global warming as having a political agenda by default is also not a good thing, and I also agree about the political prostitution of environmental science.
Permalink to Comment5. DCRogers on October 2, 2007 5:18 PM writes...
milkshake: ...the sceptics that dare to question the validity of key asumptions get acused of agenda...
curious waveform: ...to bin someone criticising global warming as having a political agenda by default is also not a good thing...
We're in agreement here... I'd like nothing less than returning much of the debate back into a scientific one. I must note, however, until the default expectation changed (to global warming being real), I believe that there were many people with a political agenda fighting reasoned scientific debate and study. Now that the shoe is on the other foot, some of these same people are squeeling about being squelched.
Funny how the ozone layer stuff hasn't generated the same amount of vitriol.
Permalink to Comment6. Hap on October 3, 2007 10:26 AM writes...
A problem is that most people don't have the time to learn enough relevant about everything to follow it, so they want people that they believe are right that they can trust. Institutions want trust as well, because it makes it easier for them to get what they want without question. Once something is shown to be wrong, the people that assumed it (and whoever championed it) to be correct on the basis of trust are suddenly disillusioned and unhappy, as they believe that their trust was misplaced. Science can't work on trust - it requires evidence, and always has the potential (because of evidence you didn't see, or interpreted wrongly) to prove you incorrect.
In the presence of people who have their own agendas, and people disposed to trust in matters for which it is inappropriate, trust will be misused, and used to validate or invalidate opinions without recourse to evidence. Achieving status based on the way we go about business and its effectiveness is a more robust strategy for public confidence than the "Look, we're smart (or we have lots of toys you'll like) - you can trust us." strategy that science and technology tend to use sometimes to aquire social status and money.
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