Warming could push sea levels up six meters by 2100

[HURAKAN]

Ice caps melting faster than forecast

`It's not a gradual change. It's like flipping a switch,' researcher says

New reports warn of sea levels rising up to 5 metres, extensive flooding

Global warming of only a couple of degrees Celsius projected by the end of this century is enough to trigger widespread melting of the massive Greenland ice cap and the partial collapse of Antarctica's ice sheets, prominent climate researchers warn in two studies published yesterday.

The findings are a stunning about-face from previous expert forecasts that such massive melting would take millennia to kick in, even with rising global atmospheric levels of carbon dioxide and other greenhouse gases.

This new research, based on a comprehensive look at global warming in the distant past, says melting the two icy domains could eventually raise sea level worldwide by as much as five metres, enough to flood low-lying regions like the Netherlands and most Pacific atolls, as well push half a billion people inland.

The full five-metre rise could take several centuries but the world's oceans could easily be a metre higher by 2100, the researchers said.

"The melting is going to happen faster than we thought. It's already begun to happen," said University of Calgary ice researcher Shawn Marshall, the sole Canadian among the authors of the two studies published by the journal Science.

"We could be past the point of no return for Greenland this century," he said in an interview.

A 1998 federal government report rated most of P.E.I., the eastern coast of Nova Scotia and the Beaufort Sea shore in the Western Arctic as "highly sensitive" to a global sea level rise of under seven-tenths of a metre.

Marshall and the other researchers acknowledged they were taken by surprise by the breakneck escalation in the melting of glaciers and ice sheets in recent years. Since 1980 the portion of the Greenland ice cap experiencing annual melting has increased by 40 per cent.

"It's not a gradual change. It's like flipping a switch. Areas that haven't experienced melt in centuries suddenly do," said Marshall.

A widely quoted report in 2001 from the Intergovernmental Panel on Climate Change concluded that major melting was no threat in Greenland and Antarctica in this century.

But Jonathan Overpeck, a climate scientist at the University of Arizona, said the new research shows these massive ice sheets are much more sensitive to global warming than originally suspected.

"Once we're above two times the pre-industrial levels of carbon dioxide we're in the danger zone," said Overpeck, who is lead author on one of the studies.


--------------------------------------------------------------------------------
`The melting is going to happen faster than we thought. It's already

begun to happen.

We could be past the

point of no return for

Greenland this century.'

Shawn Marshall, University of Calgary

--------------------------------------------------------------------------------


"Somewhere after that we'll pass a threshold where melting of the ice sheets and sea level rise is irreversible," he said.

Most experts agree that carbon dioxide concentrations double the pre-industrial level will be reached sometime after 2050 unless global emissions are at least cut in half. The current atmospheric concentration of carbon dioxide is about 380 parts per million compared to 280 parts per million before widespread burning of fossil fuels began around 1870.

Under the Kyoto Protocol, industrialized countries have pledged to reduce their overall emissions of greenhouse gases to 5 per cent below 1990 levels starting in 2008.

But soaring emissions from China and other developing countries — and the Kyoto boycott by Australia and the United States — mean that global carbon dioxide levels are expected to continue rising steadily.

The new warning is based on using climate extremes from the last major global warming to check the reliability of future climate conditions projected by complex computer models.

A prolonged hot spell began 129,000 years ago because natural orbital variations caused the Earth's northern axis to tilt more toward the sun producing much higher temperatures in the northern hemisphere, especially the Arctic.

A decade-long international research project gathered an evidence of climate change from that period, including the disappearance of glaciers in Canada's Arctic archipelago, halving of Arctic sea ice coverage, major shrinking of the Greenland ice cap and a northward march of the boreal forest.

Examination of Australia's Great Barrier Reef also indicated that sea levels were four to six metres higher than today.

A group of U.S. researchers then produced many of the same results by simulating increased sun on the northern hemisphere in an advanced climate model which Calgary's Marshall beefed up to handle glacier movements and ice melting.

"The model got it about right for the past which gives us more confidence in its forecasts," said Marshall.

A second research team, led by Overpeck, then used the souped-up model to project what would happen to the Earth's ice cover if global temperatures were raised by higher levels of carbon dioxide rather than a shift in the planet's tilt.

They found that tripling pre-industrial carbon dioxide levels by 2100 caused widespread melting in Greenland and the Arctic but didn't raise sea levels the five metres recorded in the Australia reefs. The Western Antarctic Ice Sheet must also melt, the scientists concluded.

Even a two degree Celsius rise in global average temperature would cause thermometers to soar as much as eight or 10 degrees in the Arctic and Antarctic, a feedback process known as polar amplification.

"All the things we were worrying about happening did happen and it didn't take that much warming," said Overpeck.

__________________________________________________________________________________________________________________________

Warming could push sea levels up six meters by 2100

Polar ice sheets are melting faster than expected and could push sea levels up as much as six meters by 2100, scientists warn in two new studies.

Saturday, March 25, 2006

Polar ice sheets are melting faster than expected and could push sea levels up as much as six meters by 2100, scientists warn in two new studies.
Based on current warming trends, average temperatures could jump at least 2.5 degrees Celsius by the end of the century, resembling the last great global warming surge 129,000 years ago when seas rose that much.

"This is a real eye-opener set of results," said Jonathan Overpeck of the University of Arizona, co-author of the studies with Bette Otto-Bliesner of the Colorado National Center for Atmospheric Research. "The last time the Arctic was significantly warmer than the present day, the Greenland Ice Sheet melted back the equivalent of two to three meters of sea level."

Overpeck and Otto-Bliesner used a powerful climate modeling computer, ice sheet simulation and paleoclimate data to create a picture of Earth's climate 129,000 years ago.

"These ice sheets melted before and sea levels rose. The warmth needed isn't that much above present conditions," Otto-Bliesner said. Overpeck warned "serious measures to reduce greenhouse gases" must start within the next decade.

Their studies are published in the latest issue of Science magazine.

Shawn Marshall, a glaciologist at Canada's University of Calgary who took part in the research, said warming 130,000 years ago was caused by an increase in solar radiation after changes in Earth's tilt and orbit. Today's warming, scientists say, is caused mainly by greenhouse gases.

Overpeck pointed out another apparent difference is that, in the previous period, the warmer temperatures were mostly in the Arctic and only during the summers.

Now, he said, Earth is warming year-round and at both poles.

He said that the warming danger in the Antarctic is not the overall melting of the ice cover, as would happen in Greenland.

Instead, he foresees that the Antarctic ice sheet would fracture, plunging more icebergs into the sea and raising the sea level "just like throwing a bunch of ice cubes into a full glass of water."

Recent studies have noted an accelerating melting of ice sheets and glaciers surrounding the two poles.

In a separate study, seismologists say they have detected an increase in glacial earthquakes - temblors up to a magnitude of 5.1, which they believe result from melting.

The earthquakes, many of them in the summer, involve rapid shifts in chunks of ice "as large as Manhattan." AGENCE FRANCE-PRESSE

http://www.thestar.com/NASApp/cs/Conten ... 8350116467

http://www.thestandard.com.hk/news_deta ... con_type=1

[cycloneye]

Well I wont be around by 2100 to see that if it occurs.

[jdray]

http://www.geo.arizona.edu/dgesl/resear ... se_old.htm

[P.K.]

Hmmm, can't log in via my university subscription to to see this article for some reason.

Remember it isn't just melting ice caps that could cause the sea levels to rise as the sea will expand as it warms up.

[greeng13]

Hmmm, can't log in via my university subscription to to see this article for some reason.

Remember it isn't just melting ice caps that could cause the sea levels to rise as the sea will expand as it warms up.

how is that? just wondering because my understanding is that water expands when it freezes and therefore would "shrink" when it melts. is it because the glaciers are "compacted" and more dense than typical frozen water? (i.e. an ice cube in my freezer)

[Hybridstorm_November2001]

I heard the glaciers could be gone in *GASP* as little as 1,000 years. Guess I will not get my back yard Palm Tree after all

[P.K.]

If the ice caps melt due to a warming world then sea temperatures around the world will likely be rising (Ok it is far slower than the rate the atmosphere rises) and therefore expand. Does anyone have any idea how much water is locked up at the poles compared to what is currently in the oceans?

This is something that needs to be dealt with in my part of the world as London is at threat especially with SE England sinking.

PS - Do we need so many threads on this? Although it is nice to see other people posting on this part of the forum.

[greeng13]

If the ice caps melt due to a warming world then sea temperatures around the world will likely be rising (Ok it is far slower than the rate the atmosphere rises) and therefore expand. Does anyone have any idea how much water is locked up at the poles compared to what is currently in the oceans?

This is something that needs to be dealt with in my part of the world as London is at threat especially with SE England sinking.

PS - Do we need so many threads on this? Although it is nice to see other people posting on this part of the forum.

the other one was in talkin' tropics and got moved.