greenland meltdown

Dave

The main fault with the site you mentioned

http://home.austarnet.com.au/yours/Greenhouse_Bullcrap.htm

is the way the author accepts data that he agrees with and challenges the validity of data that he disagrees with. With the ice sheets for example, he argues that Greenland and Antarctica are not contributing to a rise in sea levels, yet the link he sites does not support this contention.

http://www.abc.net.au/news/newsitems/200510/s1487477.htm


Further, he states that the ice caps would take thousands of years to melt. I guess that he would be quite chuffed to know that in believing this he is believing in a computer model! The articles I posted previously show how field observations can modify hitherto accepted ideas.

Aside from blaming "the greenies" for the devastation of New Orleans, the only bit of reasoning I found funny was the claim that a changing climate was natural, then vigorous argument that nothing is changing.

Billy

http://www.thestatesman.net/page.news.php?clid=24&theme=&usrsess=1&id=107496

Dire degrees

Steve Connor on the galloping gremlin of global warming

MAN-MADE greenhouse gases are being released into the atmosphere 30 times faster than at the time when the earth experienced a previous episode of global warming. A study comparing the rate at which carbon dioxide and methane are being emitted now compared to 55 million years ago when global warming also occurred has found dramatic differences in the speed of release.
James Zachos, professor of earth sciences at the University of California, Santa Cruz, says the speed of the current build-up of greenhouse gases is far greater than during the global warming that took place following the demise of the dinosaurs. “The emissions that caused this past episode of global warming probably lasted 10,000 years. By burning fossil fuels, we’re likely to emit the same amount over the next three centuries,” he told the American Association for the Advancement of Science in St Louis.
He warns that studies of global warming events in the geological past indicate that earth’s climate passes a threshold beyond which climate change accelerates with the help of positive feed-backs - vicious circles of warming. Professor Zachos is a leading authority on the episode of global warming known as the Palaeocene-Eocene Thermal Maximum, when average global temperatures increased by up to five degrees Celsius due to a massive release of carbon dioxide and methane. His research into the deep sediments of the ocean suggests that at this time about 4.5 billion tons of carbon entered the atmosphere over a period of 10,000 years. This will be the same amount of carbon released into the atmosphere from cars and industrial emissions over the next 300 years if present trends continue, he says.
Although carbon can be released suddenly and naturally into the atmosphere from volcanic activity, it takes many thousand of years for it to be removed permanently by natural processes such as rock weathering.
By analysing seabed sediments recovered from the international Ocean Drilling Programme, scientists estimate that during this former period of global warming it took 100,000 years for carbon dioxide levels to return to normal.
The ocean is also capable of removing carbon, and far more quickly, but this natural capacity can be quickly overwhelmed, which is probably what happened 55 million years ago. Professor Zachos says the same may soon occur with the ocean today. “The rate at which the ocean is absorbing carbon will soon decrease. Records of past climate change show that change starts slowly and then accelerates. The system crosses some kind of threshold. It will take tens of thousands of years before atmospheric carbon dioxide comes down to pre-industrial levels. Even after humans stop burning fossil fuels, the effects will be long-lasting.”
Global warming has assumed serious proportions and is causing the Greenland ice cap to disintegrate far faster than anyone has predicted. A study of the region’s massive ice sheet warns that sea levels may as a consequence rise more dramatically than expected. Scientists have found that many of Greenland’s huge glaciers are moving at an accelerating rate - dumping twice as much ice into the sea than five years ago - indicating that the ice sheet is undergoing a potentially catastrophic break-up.
The implications of the research are dramatic, given that Greenland holds enough ice to raise global sea levels by up to seven metres, a disaster scenario that would result in the flooding of some of the world’s major population centres. Satellite measurements of the entire land mass of Greenland show that the speed at which the glaciers are moving to the sea has increased significantly over the past 10 years with some glaciers moving three times faster than in the mid-1990s.
Scientists believe computer models of how the Greenland ice sheet will react to global warming have seriously under-estimated the threat posed by sea levels that could rise far more quickly than envisaged.
The latest study shows that rather than just melting relatively slowly, the ice sheet is showing all the signs of a mechanical break-up as glaciers slip ever faster into the ocean, aided by the “lubricant” of melt water forming at their base.
Eric Rignot, a scientist at the Jet Propulsion Laboratory and the California Institute of Technology in Pasadena, says computer models used by the UN’s International Panel on Climate Change haven’t adequately taken into account the amount of ice falling into the sea from glacial movements.
Yet the satellite study shows that about two-thirds of the sea-level rise caused by the Greenland ice sheet is due to icebergs breaking off from fast-moving glaciers rather than simply the result of water running off from melting ice. “In simple terms, the ice sheet is breaking up rather than melting. It’s not a surprise in itself but it is a surprise to see the magnitude of the changes. These big glaciers seem to be accelerating, they seem to be going faster and faster to the sea,” says Dr Rignot. “This is not predicted by the current computer models. The fact is the glaciers of Greenland are evolving faster than we thought and the models have to be adjusted to catch up with these observations.”
The Greenland ice sheet covers an area of 1.7 million square kilometres - about the size of Mexico - and in places is up to three kilometres thick. It formed over thousands of years by the gradual accumulation of ice and snow, but now its disintegration could occur in decades or centuries. Over the past 20 years the air temperature of Greenland has risen by three degrees Celsius and computer models have suggested that it would take at least 1,000 years for the ice sheet to melt completely. But the latest study suggests that glaciers moving at an accelerating rate could bring about a much faster change. “The behaviour of the glaciers that dump ice into the sea is the most important aspect of understanding how an ice sheet will evolve in a changing climate,” says Dr Rignot. “It takes a long time to build and melt an ice sheet, but glaciers can react quickly to temperature changes. Climate warming can work in different ways, but generally speaking, if you warm up the ice sheet, the glacier will flow faster.”
The ice “balance sheet” of Greenland is complex but in simple terms it depends on the amount of snow that falls, the amount of ice that melts as run-off and the amount of ice that falls directly into the sea in the form of icebergs “calving” from moving glaciers.
Satellites show that the glaciers in the south of Greenland are now moving much faster than they were 10 years ago. Scientists estimate that in 1996, glaciers deposited about 50 cubic km of ice into the sea. In 2005, this had risen to 150 cubic km of ice. Details of the latest study, published in the journal Science show that Greenland now accounts for an increase in global sea levels of about 0.5 millimetres per year - compared to a total sea level rise of three millimetres a year.
The Independent, London