In a major new paper in the influential journal Science, a team of researchers report strikingly good news about a thirty year old environmental problem. The Antarctic ozone “hole” — which, when it was first identified in the mid-1980s, focused public attention like few other pieces of environmental news — has begun, in their words, to finally “heal.”
“If you use the medical analogy, first the patient was getting worse and worse, and then the patient is stabilized, and now, the really encouraging thing, is that the patient is really starting to get better,” said MIT atmospheric scientist Susan Solomon, lead author of the study, and former co-chair of the United Nations’ Intergovernmental Panel on Climate Change.
And moreover, that patient — the Earth’s vital ozone layer — is getting better directly because of our choices and policies.
The initial, Nobel Prize winning discovery that ozone depleting chemicals called chlorofluorocarbons (CFCs) carried in refrigerants, spray cans, foams and other substances could damage the stratospheric layer that protects us from ultraviolet solar radiation (and thus, skin cancer) came in 1974. But it wasn’t until the sudden discovery of a vast seasonal ozone “hole” over Antarctica in 1985 that the world was shocked into action.
The so-called “hole” represents a region of the stratosphere over Antarctica, between about 10 and 25 kilometers in altitude, where “the ozone gets destroyed completely,” explains Solomon, who conducted the new research with scientists from the National Center for Atmospheric Research and the University of Leeds in the UK. However, some ozone remains above and below this region, amounting to a 40 or 50 percent loss of atmospheric ozone overall in a very large area of air.
Ozone has been depleted in the stratosphere all across the globe, to be sure. But Antarctica in the spring (which is autumn in the northern hemisphere) presents uniquely conducive conditions for it to happen, as extremely cold polar stratospheric clouds provide a surface that enables the chemical reactions in which destructive forms of chlorine are created.
Discovery of the “hole” galvanized action and in 1987, the Montreal Protocol, which is still today hailed as the epitome of a successful environmental agreement, led to a phase out of the use of ozone depleting chemicals. Here was a case that now appears so very different from the story of climate change, because everything basically functioned like it was supposed to — scientists identified a problem, the public grew concerned, and politicians acted to solve it.
“You have to put yourself back in the time when the ozone hole was discovered,” remembers Solomon, who has been studying the issue for over three decades. “We thought we were going to see a few percent change in the ozone layer in a century. And then all of a sudden, boom, we’ve got half as much ozone in a part of the world where nobody ever expected it, already happening in 1986. It became a tremendous hot environmental crisis as a result of that.”
Ever since the Montreal Protocol’s adoption, then, it has been a process of waiting for ozone depletion in the atmosphere to slow down, then for decline to cease entirely, and then finally, seeing the ozone layer turn the corner and begin to grow back. And it is this last observation that is finally here for the Antarctic ozone hole in particular, the new study asserts.
In the research, the researchers used satellite and balloon data to examine the seasonal Antarctic ozone hole for a 15-year period between 2000 and 2015. And they found that in the month of September, the size of the hole has generally declined by over 1.5 million square miles, and that this is a trend that can be statistically separated from the “noise” of natural variations.
Полная версия: https://www.washingtonpost.com/news/energy-environment/wp/2016/06/30/the-antarctic-ozone-hole-has-finally-started-to-heal-scientists-report/?wpisrc=al_alert-hse
