The Blanket Effect is intended for others to learn about weather modification and its related subjects in an easy to understand way. Started in 2005, this blog is a work in progress as the technology advances

November 3, 2007

Caustic Clouds

(note: Abridged from: Conservation Science Institute)

Research by Cambridge University shows that it is not increased pollution but a side effect of climate change that is making ozone depletion worse. At high altitudes, 50% of the protective layer had been destroyed.

The research has dashed hopes that the ozone layer was on the mend. Since the winter of 1999-2000, when depletion was almost as bad, scientists had believed an improvement was under way as pollution was reduced. But they now believe it could be another 50 years before the problem is solved.

What appears to have caused the further loss of ozone is the increasing number of stratospheric clouds in the winter, 15 miles above the earth.

These clouds, in the middle of the ozone layer, provide a platform which makes it easier for rapid chemical reactions which destroy ozone to take place.

This year, for three months from the end of November, there were more clouds for longer periods than ever previously recorded.
(image from Conservation Science Institute, for detail click image)

"The pollution levels have leveled off but changes in the atmosphere have made it easier for the chemical reactions to take place that allow pollutants to destroy ozone.

With these changes likely to continue and get worse as global warming increases, then ozone will be further depleted even if the level of pollution is going down."

The relationship between the depletion of the ozone layer and climate change is so complex that the EU is investing £11m in a five-year project to try to understand and predict what is happening.

Reporting the results of the first year, the scientists told the meeting in Vienna yesterday that "the atmospheric lifetime of these [ozone depleting] compounds is extremely long and the concentrations will remain at dangerously high levels for another half century."

Increased greenhouse gases in the air trap more heat in the lower atmosphere, but the stratosphere far above the earth is getting colder. As a result, ice clouds form between 14 and 26 kilometers above the earth, exactly in the region where the protective ozone is found.

The European scientists reported the first signs of ozone loss in January. As sunlight returned to northern latitudes, the rate of ozone depletion increased and rapid destruction of ozone occurred throughout February and March.

In the altitude range where the ozone layer usually reaches its maximum concentration, more than half of the ozone was lost. In the lower atmosphere losses were not so great.

(image above from
Conservation Science Institute)

"Overall, about 30% of the ozone layer was destroyed," said Dr Markus Rex, from the Alfred Wegener Institute in Potsdam, Germany, another member of the team.

He said the cold conditions which created polar stratospheric clouds were four times more extensive in 2005 than in the 1960s and 70s.

Professor Pyle said overall the mixing of the air in the northern hemisphere was far more rapid than in the Antarctic so a "hole" in the ozone layer did not occur.

Instead, as the air mixed in spring, there was a general thinning of the protective ozone over the whole of the northern hemisphere.

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