Science, Tech & Environment

Ozone levels over the Arctic hit all-time low

There's an odd feeling of déjà vu these days here on the environment beat. First came the awful events in Japan with a nuclear disaster on a scale unseen since Chernobyl in the 1980s. Now comes news about atmospheric ozone that takes us back to the 80s as well.

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At a meeting in Vienna Tuesday, scientists with the UN's World Meteorological Organization reported that ozone levels over the Arctic were down as much as 40 percent at the end of the northern winter just a few weeks ago. That's roughly a third worse than the previous low, and it's bad news for people in much of the northern hemisphere, because it means a lot more of the sun's damaging ultraviolet radiation may be hitting many of us.

Scientists say this new ozone "hole" could pass as low as 40 degrees latitude, which includes most of Europe and Russia, all of Canada, and parts of the US as far south as New York. It's hard to know exactly if, when, or how much we'll be affected unless our local weather guy happens to provide UV radiation forecasts, so the prudent thing for people in this part of the world to do over the next few weeks is take extra care to protect our eyes and skin by wearing sunscreen and sunglasses when we go out.

Ozone depletion was one of the big stories back in the '80s when I first started covering the environment beat. Ozone is a rare and fragile form of oxygen that protects the earth from some of the sun's damaging radiation, and it turned out that what we thought were harmless chemicals used in everything from spray cans to refrigerators were getting up into the high atmosphere and destroying it.

It was a global lesson in unintended consequences, and the globe actually came together in 1987 to sign a groundbreaking agreement called the Montreal Protocol to slowly phase out the chemicals. Problem is, some of them are still being used, and the ones already in the atmosphere linger for decades, so it will be at least the middle of this century before things return to their old equilibrium.

Meanwhile, the focus of the problem is shifting from the southern hemisphere to the northern. Back in the '80s, the problem was worst over Antarctica and high southern latitudes. That's because atmospheric circulation patterns concentrate ozone-eating chemicals over the poles, and extremely low temperatures high above Antarctica speed up the reaction. Apparently the change these days is not so much that the problem has gone away down there as that it's growing up here. Turns out there's an unfortunate confluence of two problems–ozone-eating chemicals in the atmosphere, and changing atmospheric temperatures due to climate change.

Surface temperatures in the Arctic are warming up, but that's causing temperatures to drop high above in the atmosphere. And at those colder temperatures, those pollutants in the atmosphere are able to destroy more ozone. Scientists have known for a long time that this would happen, it was just a matter of when. This past winter the air high up over the arctic was especially cold, so "when" is now.

The good news is that however thin the ozone layer might get over where you live, scientists are saying it's likely to last only a few days, and that in any case, the ozone layer will start to build itself back up again as the northern spring progresses. The bad news is that this is a problem we might have to live with on and off for years to come. UN officials project that even with the chemical phase-out, ozone levels won't return to normal for decades.

And it's all a reminder not just of a time that already seems so long ago, but of the daunting nature of the challenges ahead. In retrospect, the problem of ozone depletion was an easy fix – a relatively confined problem, caused by pollutants that were marginal to the global economy and easily replaced. And yet it will still take the better part of a century for the disturbance to shake out, for the system to return to normal and for the threat to humans and other creatures to pass.

Compare that to something like climate change, the biggest environmental challenge of our time. The system that's being disturbed is infinitely more complex, the pollutants involved are ubiquitous and central to economic life as we know it, and the global consensus on how, when and even whether to break away from business as usual can seem as elusive as ever.

The "return" of the ozone problem reminds us of the complexity of the natural systems that we depend on, of our inability to control and predict events once we've knocked things out of whack, and of the dangers of waiting to take action once we've started to realize how badly we've messed things up. Even if the world came together tomorrow in a sudden climate epiphany, it would take not decades but centuries to restore something like the balance that we're already destroying.

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