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Even after emissions drop, effects could last 1000 years!

 
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BeitragVerfasst am: Di Jan 27, 2009 6:43 pm    Titel: Even after emissions drop, effects could last 1000 years! Antworten mit Zitat

Even after emissions drop, peak effects could last 1,000 years!
By Cornelia Dean
January 27, 2009

Many people who worry about global warming hope that once emissions of heat-trapping gases decline, the problems they cause will quickly begin to abate.

Now researchers are saying that such hope is ill founded, at least with regard to carbon dioxide.

Because of the way carbon dioxide persists in the atmosphere and in the oceans, and the way the atmosphere and the oceans interact, patterns that are established at peak levels will produce problems like "inexorable sea level rise" and Dust-Bowl-like droughts for at least a thousand years, the researchers are reporting in the Proceedings of the National Academy of Sciences.

"That peak would be the minimum you would be locking yourself into," said Susan Solomon, a senior scientist at the National Oceanic and Atmospheric Administration, who led the work.

The researchers describe what will happen if the atmospheric concentration of carbon dioxide - the principal heat-trapping gas emission - reaches 450 to 600 parts per million, up from about 385 ppm today. Most climate researchers consider 450 ppm virtually inevitable and 600 ppm difficult to avoid by midcentury if the use of fossil fuels continues at anything like its present rate.

At 450 ppm, the researchers say, rising seas will threaten many coastal areas, and Southern Europe, North Africa, the Southwestern United States and Western Australia could expect 10 percent less rainfall.

"Ten percent may not seem like a high number," Solomon said Monday, "but it is the kind of number that has been seen in major droughts in the past, like the Dust Bowl."

At 600 ppm, there might be perhaps 15 percent less rain, she said.

In 1850, atmospheric carbon dioxide was roughly 280 ppm, a level scientists say had not been exceeded in at least the previous 800,000 years.

In their paper, Solomon and her colleagues say they confined their estimates to known data and effects. For example, they based their sea level estimates largely on the expansion of seawater as it warms, a relatively straightforward calculation, rather than including glacial runoff or melting inland ice sheets - more difficult to predict but potentially far greater contributors to sea level rise.

The new work dealt only with the effects of carbon dioxide, which is responsible for about half of greenhouse warming. Gases like chlorofluorocarbons and methane, along with soot and other pollutants, contribute to the rest. These substances are far less persistent in the atmosphere; if these emissions drop, their effects will decline relatively fast.

Michael Oppenheimer, a geoscientist at Princeton, praised the report in an e-mail message as a "remarkably clear and direct" discussion of whether it would be possible to temporarily exceed a level like 450 ppm and then reduce emissions in time to avoid catastrophic events like the collapse of a major inland ice sheet.

Oppenheimer said the new analysis showed that "some dangerous consequences could be triggered and persist for a long, long time, even if emissions were cut radically."

"Policy makers need to understand," he continued, "that in some ways once we are over the cliff, there's nothing to stop the fall."

Solomon said it would be wrong to view the report as evidence that it was already too late to do much good.

"So if we slow it down," she said, "we have more time to find solutions."

Bush's fishing limits praised!

Ocean conservationists are hailing former President George W. Bush for passing tough rules to end the overfishing of 40 marine species before he left the White House, The Associated Press reported from New Orleans on Tuesday.

Under the new rules, the nation's regional fishery management councils will be forced to draw up measures to end overfishing by 2010. In most instances, this would involve putting caps on how many fish can be caught each year.

http://www.iht.com/articles/2009/01/27/america/carbon.1-416529.php
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