ozone hole

Antarctic ozone hole may have larger role in climate change

A new paper published yesterday in Science magazine claims that the Antarctic ozone hole has more influence on climate than previously thought.

The abstract reads:

Over the past half-century, the ozone hole has caused a poleward shift of the extratropical westerly jet in the Southern Hemisphere. Here, we argue that these extratropical circulation changes, resulting from ozone depletion, have substantially contributed to subtropical precipitation changes. Specifically, we show that precipitation in the Southern subtropics in austral summer increases significantly when climate models are integrated with reduced polar ozone concentrations. Furthermore, the observed patterns of subtropical precipitation change, from 1979 to 2000, are very similar to those in our model integrations, where ozone depletion alone is prescribed. In both climate models and observations, the subtropical moistening is linked to a poleward shift of the extratropical westerly jet. Our results highlight the importance of polar regions on the subtropical hydrological cycle.

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 According to the press release from Columbia University:

While previous work has shown that the ozone hole is changing the atmospheric flow in the high latitudes, the Columbia Engineering paper, “Impact of Polar Ozone Depletion on Subtropical Precipitation,” demonstrates that the ozone hole is able to influence the tropical circulation and increase rainfall at low latitudes in the Southern Hemisphere. This is the first time that ozone depletion, an upper atmospheric phenomenon confined to the polar regions, has been linked to climate change from the Pole to the equator.

“The ozone hole is not even mentioned in the summary for policymakers issued with the last IPCC (Intergovernmental Panel on Climate Change) report,” noted Polvani, professor of Applied Mathematics and of Earth & Environmental Sciences, senior research scientist at the Lamont-Doherty Earth Observatory, and co-author of the paper. “We show in this study that it has large and far-reaching impacts. The ozone hole is a big player in the climate system!” The ozone hole is now widely believed to have been the dominant agent of atmospheric circulation changes in the Southern Hemisphere in the last half century. This means, according to Polvani and Kang, that international agreements about mitigating climate change cannot be confined to dealing with carbon alone— ozone needs to be considered, too.

The authors claim, “While the ozone hole has been considered as a solved problem, we’re now finding it has caused a great deal of the climate change that’s been observed.” This would seem to downplay the role of carbon dioxide.

Be aware that this is a computer modeling study. Only time will tell if it holds up under scrutiny.

Complete paper here.

 

Sunburned Whales and Ozone

A British study of whales in the Gulf of California reports that light-skinned whales show signs of sunburn. The researchers attribute this to thinning of the ozone layers which protect us from ultraviolet radiation.

A curious thing about this study, which was conducted from 2007 to 2009, is that the number of whales exhibiting signs of sunburn greatly increased over the three-year study: in 2007, 12% of the whales had blisters; in 2008, 28% had blisters; and in 2009, 68% had blisters. This large increase in blistering would suggest that the ozone layer is rapidly decreasing. Yet NASA says “UV exposure has increased over the last 30 years, but stabilized since the mid-1990s.” Obviously, these researchers need more government grants to take more tropical cruises to further study this problem.

Since the 1970s, scientists hypothesized that chlorine compounds could react in the atmosphere to decrease the protective layer of ozone (O3) which blocks some of the ultraviolet rays impinging on the earth. In 1985, scientists noticed that the ozone layer over the Antarctic was very thin. (Later research would find that this thinning is an annual event and also varies on longer cycles.) This discovery caused a political furor and in 1987, the Montreal Protocol banned chloro-fluoro-carbons (CFCs) aka freon, from air conditioners and refrigerators.

The claim that CFCs were responsible for the perceived thinning remains controversial. In 2007 chemists poked holes in the ozone theory in a study published in Nature. These researchers found that the decomposition of chlorine compounds by light was much slower than had been assumed and “at least 60% of ozone destruction at the poles seems to be due to an unknown mechanism.”

What could this unknown mechanism be? In 2009, in a paper published in Physical Review Letters found a correlation between cosmic rays and ozone depletion. The abstract says:

“This Letter reports reliable satellite data in the period of 1980–2007 covering two full 11-yr cosmic ray (CR) cycles, clearly showing the correlation between CRs and ozone depletion, especially the polar ozone loss (hole) over Antarctica. The results provide strong evidence of the physical mechanism that the CR-driven electron-induced reaction of halogenated molecules plays the dominant role in causing the ozone hole. Moreover, this mechanism predicts one of the severest ozone losses in 2008–2009 and probably another large hole around 2019–2020, according to the 11-yr CR cycle.”

If these two research groups are right, then once again, a trumped-up environmental crisis is proven to be false and we went to the expense of banning CFCs for nothing.