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Politics : The Exxon Free Environmental Thread -- Ignore unavailable to you. Want to Upgrade?

To: Wharf Rat who wrote (1252)	9/28/2007 4:56:28 PM
From: Skywatcher	Respond to of 49038

no kidding.....

To: Wharf Rat who wrote (1252)	9/29/2007 6:09:43 AM
From: Wharf Rat	Read Replies (1) \| Respond to of 49038

Arctic thaw may be at "tipping point" Fri Sep 28, 2007 9:24am EDT By Alister Doyle, Environment Correspondent OSLO (Reuters) - A record melt of Arctic summer sea ice this month may be a sign that global warming is reaching a critical trigger point that could accelerate the northern thaw, some scientists say. "The reason so much (of the Arctic ice) went suddenly is that it is hitting a tipping point that we have been warning about for the past few years," James Hansen, director of NASA's Goddard Institute for Space Studies, told Reuters. The Arctic summer sea ice shrank by more than 20 percent below the previous 2005 record low in mid-September to 4.13 million sq km (1.6 million sq miles), according to a 30-year satellite record. It has now frozen out to 4.2 million sq km. The idea of climate tipping points -- like a see-saw that suddenly flips over when enough weight gets onto one side -- is controversial because it is little understood and dismissed by some as scaremongering about runaway effects. The polar thaw may herald a self-sustaining acceleration that could threaten indigenous peoples and creatures such as polar bears -- as Arctic sea ice shrinks, the darker ocean soaks up ever more heat than reflective snow and ice. In Germany, the Potsdam Institute for Climate Impact Research says Arctic sea ice has "already tipped." Among potential "tipping elements" that are still stable, it lists on its Web site a melt of Siberian permafrost, a slowdown of the Gulf Stream and disruptions to the Indian monsoon. "I'd say we are reaching a tipping point or are past it for the ice. This is a strong indication that there is an amplifying mechanism here," said Paal Prestrud of the Center for International Climate and Environmental Research in Oslo. "But that's more or less speculation. There isn't scientific documentation other than the observations," he said. SHIPPING, POLAR BEARS Many experts now reckon Arctic ice may disappear in summer before mid-century, decades before earlier forecasts. The thaw would open the region to oil and gas exploration or shipping. Reuters will host a summit of leading newsmakers on Oct 1-3 to review the state of the environment. Speakers will include Rajendra Pachauri, the head of the U.N. Climate Panel and Michael Morris, chief executive of American Electric Power. "All models seem to underestimate the speed at which the ice is melting," said Anders Levermann, a Potsdam professor. "I do not believe that this is alarmist... not all tipping points are irreversible," he said. And societies can weigh up remote risks, such as planes crashing or nuclear meltdowns. Hansen said he is seeking more study of causes of the melt, widely blamed on greenhouse gases from burning fossil fuels but perhaps slightly stoked by soot from forest fires or industries in Russia and China. Ice darkened by soot melts faster. "It is a very good lesson, because the ice sheets (on Greenland and Antarctica) have their own tipping points, somewhat harder to get started but far more dangerous for humanity around the globe," he said. A melt of floating Arctic sea ice does not affect sea levels but Greenland has enough ice to raise oceans by 7 meters and Antarctica by about 57 meters, according to U.N. estimates. Pachauri's authoritative climate panel, in a summary report due for release in November, does not use the phrase "tipping point" but does say: "Climate change could lead to abrupt or irreversible climate changes and impacts." It says, for instance, that it is "very unlikely" that the Gulf Stream bringing warm water north to Europe will switch off this century. That could bring a big regional cooling. And it says that a melt of ice sheets could lead to big sea level rises over thousands of years. "Rapid sea level rise on century time scales cannot be excluded," it adds. reuters.com

To: Wharf Rat who wrote (1252)	9/29/2007 6:15:55 AM
From: Wharf Rat	Read Replies (1) \| Respond to of 49038

NASA Finds Greenland Snow Melting Hit Record High In High Places by Staff Writers Greenbelt MD (SPX) Sep 26, 2007 A new NASA-supported study reports that 2007 marked an overall rise in the melting trend over the entire Greenland ice sheet and, remarkably, melting in high-altitude areas was greater than ever at 150 percent more than average. In fact, the amount of snow that has melted this year over Greenland could cover the surface size of the U.S. more than twice. Marco Tedesco, a research scientist at the Joint Center for Earth Systems Technology, cooperatively managed by NASA's Goddard Space Flight Center in Greenbelt, Md., and the University of Maryland at Baltimore County, used satellite data to compare average snow melting from 1988-2006 with what has taken place this summer. He found that in high altitude areas over 1.2 miles above sea level, the melting index -- an indicator of where melting is occurring and for how long - was significantly higher than average. Melting over those areas occurred 25-30 days longer this year than the observed average in the previous 19 years. "When snow melts at those high altitudes and then refreezes, it can absorb up to four times more energy than fresh, unthawed snow," said Tedesco. "This can affect Earth's energy budget by changing how much radiation from the sun is absorbed by the Earth versus that reflected back into the atmosphere. Refrozen snow can also alter the snow density, thickness and snow-water content." Tedesco's findings were published Sept. 25 in the American Geophysical Union's Eos newspaper. Researchers determine the melting index by multiplying how long melting took place by the area where the increased melting took place. According to Tedesco, melting in April and May of this year in high-altitude areas was very low, but in June melting jumped unexpectedly and led to the record melting index for the year. "This record melting index in those areas came as a bit of a surprise, showing us, once again, the extreme variability and complexity of these processes," said Tedesco. His expertise in documenting melting trends produced other recent studies on increased snow melting over Greenland and the Antarctic. The data collected by the Special Sensor Microwave Imagers on the Defense Meteorological Satellite Program satellites provided Tedesco with insight into how much of an electromagnetic signal was naturally emitted by snow and ice in areas beneath the satellite overpass. The microwave instruments can detect melting above and below the snow surface. The data were processed at the National Snow and Ice Data Center in Boulder, Colo., in just 24 hours after the satellite overpass, enabling Tedesco to quickly spot changes that could signal a melting trend or new record. Tedesco's work also confirmed that the melting index this year in lower altitude areas of Greenland, though not record breaking, was higher than average by 30 percent, placing 2007 in fifth place for the highest melting index after 2005, 2002, 1998 and 2004, in that order. "Increases in the overall melting trend over Greenland have an impact that stretches beyond its icy shores," said Tedesco. "Aside from contributing to direct sea level rise, melting especially along the coast can speed up glaciers since the meltwater acts like a lubricant between the frozen surface and the bedrock deep below. The faster glaciers flow, the more water enters the ocean and potentially impacts sea level rise." Tedesco, along with U.S. and European colleagues, plans to combine satellite data with related climate model results. He plans to visit Greenland in 2008 to compare his findings from space-borne data with those obtained by ground-based sensors, all with an eye to gathering further clues of what is happening on Greenland. terradaily.com