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4.28.2005

Ozone and tsunami fears

The following articles appeared on Signs of the Times

Ozone layer most fragile on record

Fears over increase in skin cancer as scientists report that climate change continues to destroy the earth's protection

Paul Brown, environment correspondent
Wednesday April 27, 2005
The Guardian

The protective ozone layer over the Arctic has thinned this winter to the lowest levels since records began, alarming scientists who believed it had begun to heal.

The increased loss of ozone allows more harmful ultraviolet light to reach the earth's surface, making children and outdoor enthusiasts such as skiers more vulnerable to skin cancer - a disease which is already dramatically increasing.

Scientists yesterday reinforced the warning that people going out in the sun this summer should protect themselves with creams and hats.

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.

Cambridge University scientists said yesterday that, in late March, when ozone depletion was at its worst, Arctic air masses drifted over the UK and the rest of Europe as far south as northern Italy, giving significantly higher doses of ultraviolet radiation and sunburn risk.

The results, which were announced at a Geophysical Union meeting in Vienna yesterday, are part of a European venture coordinated by Cambridge University's chemistry department, which has been studying the relationship between the ozone layer and climate change since May 2004.

Yesterday, Professor John Pyle, from the university, said: "These were were the lowest levels of ozone recorded since measurements began 40 years ago. We thought things would start to get better because of the phasing out of CFCs and other chemicals because of the Montreal protocol, but this has not happened.

"The pollution levels have levelled 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 kilometres above the earth, exactly in the region where the protective ozone is found.

Not only are ozone depleting compounds an issue, but also that there are times in the past when the ozone layer has dissipated as well. The timing of this is cyclical in nature...

LAKE TAHOE
Quake in lake could cause 30-foot tsunami
Major temblors hit area in 3,000-year cycles, scientists say

David Perlman, Chronicle Science Editor

Thursday, April 28, 2005

Major quakes on seismic faults that run beneath Lake Tahoe have ruptured the earth's crust there roughly every 3,000 years or so, and scientists are trying to determine just when the last big one hit.

Although the temblors may be few and far between, they've thrust masses of ground up or down by 10 feet or more in the past, say the scientists, who have dug trenches where past quakes have struck on the shore of the Nevada community of Incline Village.

A team headed by geophysicist Graham Kent of the Scripps Institute of Oceanography at UC San Diego has probed through thick sediments of the lake bottom to reveal the bedrock underneath -- and has traced, in unprecedented detail, segments of three major faults that extend beyond the lake and onto the land.

The work supports the conclusion published four years ago by a team from the University of Nevada at Reno: that a major quake might some day generate a Lake Tahoe tsunami three stories tall.

Kent's team has found that the Incline Village fault thrusts east on the lake bottom and runs just a few steps from the Incline Elementary School on land. Near the school, there's a well-defined cliff-like scarp some 30-feet high created by many past quakes. A deep trench has been dug there by another team of scientists, led by Gordon G. Seitz of San Diego State University, to analyze the long-buried remains of old trees to determine the date of the last major quake there.

Right now, Kent said Wednesday in an interview, the date is still uncertain, and Seitz is working on refining it. "It was somewhere between a few thousand and 20,000 years ago," he said, "but Seitz should know very soon."

Kent and his team of 15 scientists reported their findings in the May issue of the journal Geology and are discussing their project this week with other quake specialists at a meeting of the Seismological Society of America at Incline Village.