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Severni pol bez leda već 2040?
http://www.b92.net/info/vesti/index.php?yyyy=2006&....._id=223261
12. decembar 2006. | 08:23 | Izvor: Beta
Toronto -- Severni pol bi mogao sasvim ostati leti bez leda već 2040. godine ako se nastavi otopljavanje klime, smatraju naučnici.
Istraživanjem čiji je rezultat objavljen u kanadskom naučnom časopisu "Džiofizikal riserč leters", utvrđeno je da se led na Severnom ledenom okeanu sve više povlači tokom leta.
"Već smo svedoci nestanka leda na moru, ali naše istraživanje ukazuje da nestanak u narednih decenija može biti znatno dramatičniji od bilo čega što se ikada desilo", rekla je koordinatorka istraživanja Marika Holand iz Nacionalnog centra SAD za istraživanje atmosfere.
"Te promene su iznenađujuće brze", upozorila je ona.
U studiji se ukazuje da ako se nastavi gomilanje gasova u atmosferi od sagorevanja fosilnih goriva, septembra 2040. godine će ostati led samo u uskom pojasu uz obalu Grenlanda i Kanade, dok će većina arktičkog područja biti bez leda.
Po računici naučnika, led koji septembra svake godine zahvata oko šest miliona kvadratnih kilometara, za deset godina će se povući na dva miliona kvadratnih kolometara, dok će zimi debljina leda sa sadašnjih oko 3,7 metara, opasti na manje od metra.
Kako se led povlači, okean prenosi sve više toplote ka Severnom polu, a voda bez leda upija sve više sunčeve toplote, te se zagrevanje ubrzava što vodi sve većem topljenju leda, rekla je Holandova.
Arctic ice could disappear in summer by 2040: study
Last Updated: Monday, December 11, 2006 | 5:16 PM ET
CBC News
Global warming could melt almost all of the ice in the Arctic during the summer months by the year 2040, according to a study to be published Tuesday.
If greenhouse gases continue to build at their current rate, the study found, the Arctic's ice cover would go through periods of stability followed by abrupt retreat.
The top image, based on simulations produced by the Community Climate System Model, shows the approximate extent of Arctic sea ice in September. By about 2040 (image at bottom), the Arctic may be nearly devoid of sea ice during the late summer unless greenhouse gas emissions are significantly curtailed. (UCAR)
One simulation projects that by 2040, only a small amount of perennial ice would remain on the north coasts of Greenland and Canada during the summer months.
This would be a more dramatic change in Arctic climate than anything we've seen so far, according to McGill University professor Bruno Tremblay, one of the study's authors. And it would also have a profound impact on global warming around the world, he said.
"Open water absorbs more sunlight than does ice," Tremblay told CBC News Online. "This means that the growing regions of ice-free water will accelerate the warming trend."
The melting of polar ice creates a positive feedback loop, Tremblay said. Higher temperatures means less ice, and that means more sunlight is absorbed by water, which in turn raises temperatures. This will lead to an accelerated change in climate in a very short time, Tremblay said.
http://www.cbc.ca/technology/story/2006/12/11/arctic-greenhouse.html
Dopuna: 12 Dec 2006 9:15
A evo vesti koja bi, apsurdno, mogla da pomogne:
"Nuklearna zima", izazvana atomskim eksplozijama, bi mogla da ohladi planetu
Small nuclear war could lead to cooldown
By ALICIA CHANG, AP Science Writer
Mon Dec 11, 6:55 PM ET
SAN FRANCISCO - Some of the scientists who first advanced the controversial "nuclear winter" theory more than two decades ago have come up with another bleak forecast: Even a regional nuclear war would devastate the environment. ADVERTISEMENT
Using modern climate and population models, researchers estimated that a small-scale nuclear conflict between two warring nations would cause 3 million to 17 million immediate casualties and lead to a marked cooldown of the planet that could lead to crop failures and further misery.
As dire as the predictions seem, they fall short of nuclear winter. That theory says that smoke and dust from an atomic war between the superpowers would blot out the sun, plunge the Earth into the deep freeze and cause mass starvation, wiping out 90 percent of the Earth's population, or billions of people.
The new scenario offers no estimate of the number of deaths from the environmental effects of a regional nuclear war.
Still, scientists said the scenario points to the danger of small nuclear states obtaining atomic warheads.
The study, presented Monday at an American Geophysical Union meeting in San Francisco, was described as the first to document in detail the climatic effects of a nuclear war on a regional scale.
Some climate experts not connected with the research questioned some of the assumptions made in the studies.
For example, the studies assume that smoke is mostly made up of soot. But other organic particles could cause smoke to scatter and not stay aloft in the atmosphere as long, lessening the impact, said scientist Steve Ghan of the Pacific Northwest National Laboratory.
"I think the effects of the smoke are exaggerated, but it does give people pause to think about," Ghan said. "It suggests that anyone who is contemplating attacking another country is not going to be immune to the impacts on their own countries."
The late astronomer Carl Sagan and four colleagues developed the nuclear winter theory, calculating in 1983 the possible effects of an all-out nuclear attack between the United States and the former Soviet Union. Other scientists have disputed the degree of damage to the Earth.
The superpowers' nuclear stockpiles have shrunk considerably since the end of the Cold War. But some of the scientists behind the nuclear winter theory — including Brian Toon of the University of Colorado at Boulder and Richard Turco of the University of California, Los Angeles — decided to revisit the topic in light of more recent world tensions.
In October,
North Korea announced that it had tested a nuclear bomb.
Iran is also pursuing the development of nuclear weapons. Other members or presumed members of the nuclear club include India, Pakistan and
Israel.
The new studies looked at the consequences if two nations dropped 50 Hiroshima-size bombs on each other's big cities. By analyzing population data and distance from blast, scientists predicted a regional nuclear war would kill 3 million people in Israel and up to 17 million in China. The U.S. would see 4 million blast deaths.
But the researchers say black soot from the fires would linger in the atmosphere, blocking the sun's rays and causing average global surface temperatures to drop about 2 degrees Fahrenheit in the first three years. Although the planet would see a gradual warming within a decade, it would still be colder than it was before the war, the scientists said.
The cooldown would shorten the growing season by about a month in parts of North America, Europe and Asia. Normal rainfall patterns such as summer monsoons in Africa and Southeast Asia would be disrupted, possibly causing huge crop failures.
In addition, the ozone layer, which keeps out harmful ultraviolet radiation, would shrink more than 20 percent, with the poles seeing a 70 percent reduction.
http://news.yahoo.com/s/ap/20061211/ap_on_sc/nuclear_winter
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