Green Blog: The Enduring Effects of Ozone Depletion

One of the most sobering realities of climate change is that even if all greenhouse gas emissions? came to an abrupt halt tomorrow, climbing temperatures, rising seas and extreme weather would still be in the global forecast for perhaps hundreds of years because of the carbon dioxide already released into the atmosphere.

To get some perspective, the story of the ozone hole over Antarctica illustrates how even a relatively small perturbation in the atmosphere can have wide-reaching and long-lasting consequences.

International action was taken within just two years of the discovery of the patch of thinning ozone in 1985 to put an end to the release of chlorofluorocarbons, or CFCs ? an organic compound that was used in refrigerants and aerosols and is the main culprit in ozone depletion. But scientists are still discovering the rippling effects of that CFC pollution decades later.

Two papers published online on Thursday in the journal Science highlight how the hole in the ozone layer, which is beginning to recover because of limits imposed on CFCs, is influencing major wind patterns, ocean circulation, concentrations of carbon in the atmosphere? and even rainfall in the Amazon.


Sukyoung Lee and Steven Feldstein, professors at Penn State, provide evidence that the depletion of the ozone layer, even more than greenhouse gas emissions, is contributing to the observed movement of the southern jet stream toward the pole. This leads, among other effects, to unusual rainfall patterns in the subtropics.

Just how the hole in the ozone causes a shift in the southern jet stream is not well understood.? Generally speaking, however, ozone absorbs ultraviolet radiation and therefore warms the atmosphere.

A decline in ozone therefore leads to less absorption and less heating, which cools the polar lower stratosphere. This has an impact on the winds in the troposphere ? the lowest 10 kilometers, or six miles, of the atmosphere.

In the same issue of Science, Darryn Waugh, a climate scientist at Johns Hopkins University, and colleagues present research ?showing that the hole in the ozone layer and its effects on wind patterns are in turn amplifying ocean currents that move surface water from the pole deeper into the ocean. As the water moves toward the Equator, it brings water from deep in the ocean up to the surface at the pole.?

Dr. Waugh tracked concentrations of CFC-12 to determine how recently water had been at the ocean?s surface.

?The water from deep in the ocean may not have seen the surface for hundreds of years,? Dr. Waugh said. ?This ?old? water is very carbon-rich, from dead organic matter that sinks to the bottom of the ocean.?

When water that is already high in carbon dioxide is pulled to the surface, the ocean in this area absorbs less carbon

?Is it good?? Is it bad? I guess that depends whether you care more about preventing ocean acidification or reducing atmospheric carbon,? Dr. Waugh said. ?Probably we should care about both. What is certain is that it?s having a significant impact on the carbon cycle.?

Around 40 percent of the absorption of carbon into the ocean has been thought to occur at the high southern latitudes, he noted, which makes this significant.

Last winter, the ozone hole was smaller than it had been for a long time. It may fully recover by 2060.

But the studies underline how even the quick international response to the threat back in the 1980s could not prevent decades of damage from continuing to unfold.

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This post has been revised to reflect the following correction:

Correction: February 1, 2013

An earlier version of this post misspelled the first name of a Penn State professor. He is Steven, not Stephen, Feldstein.

Source: http://green.blogs.nytimes.com/2013/02/01/from-ozone-depletion-enduring-effects/?partner=rss&emc=rss

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