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  PlanetArk 2 May 07
Arctic Ice Cap Melting 30 Years Ahead of Forecast
Story by Deborah Zabarenko, Environment Correspondent

Yahoo News 1 May 07
Study: Arctic sea ice melting faster

Arctic sea ice is melting three times faster than many scientists project, U.S. researchers reported Monday, just days ahead of the next major international report on climate change.

Scientists at the National Center for Atmospheric Research and the University of Colorado in Boulder concluded, using actual measurements, that Arctic sea ice has declined at an average rate of about 7.8 percent per decade between 1953 and 2006.

By contrast, 18 computer models used by the Intergovernmental Panel on Climate Change, a U.N.-sponsored climate research group, estimated an average rate of decline of 2.5 percent per decade over the same period, the researchers said.

International delegates are meeting in Bangkok, Thailand, this week to hammer out the final wording of the third IPCC report.

Both the observations cited in the new study and projections from the IPCC computer models are for September, when Arctic sea ice is typically at its low point for the year.

For March, when the ice is typically at its most extensive, the new study found the rate of decline was 1.8 percent per decade, about three times larger than the mean from the computer models.

The researchers said their observations indicate the retreat of summertime Arctic sea ice is about 30 years ahead of the pace projected by climate models.

"While the ice is disappearing faster than the computer models indicate, both observations and the models point in the same direction: the Arctic is losing ice at an increasingly rapid pace and the impact of greenhouse gases is growing," said NCAR scientist Marika Holland, one of the study's co-authors.

Gavin Schmidt, a climate researcher at the Goddard Institute for Space Studies who wasn't involved in the study, said the study is "a good reminder that uncertainty in model projections cuts both ways."

Critics of some global warming scenarios say the models exaggerate the potential problems.

"My feeling (along with the authors) is that it is likely that the models are insufficiently sensitive," Schmidt said in an e-mail to The Associated Press. He said the reasons for the lack of sensitivity are unclear.

"Overall, the models have a track record of getting large scale changes right, particularly in temperatures, but at the regional scale (like in the Arctic), there is more variability," he wrote.

The Boulder-based researchers used a combination of early reports from aircraft and ships and more recent satellite measurements to come up with their observations of the ice melt.

They said the discrepancy between their observations and computer projections indicate computer models may have failed to portray the entire impact of increasing levels of greenhouse gases such as carbon dioxide in the atmosphere.

The computer models indicated that increased greenhouse gases and natural climate variations were about equally responsible for ice loss between 1979 and 2006, the researchers said.

They said their own study indicates greenhouse gases may have a "significantly greater" role than the models suggested.

A number of factors may lead the computer models to underestimate the rate of decline in sea ice, the researchers said. Several models overestimated the thickness of the ice, and the models may have failed to fully account for changes in currents in the atmosphere and oceans that transfer heat to polar regions, they said.

The study, "Arctic Sea Ice Decline: Faster Than Forecast," will appear in the online edition of Geophysical Research Letters on Tuesday, three days before the IPCC issues its report.

On the Net: Geophysical Research Letters: http://www.agu.org/journals/gl/ Intergovernmental Panel on Climate Change: http://www.ipcc.ch/

PlanetArk 2 May 07
Arctic Ice Cap Melting 30 Years Ahead of Forecast
Story by Deborah Zabarenko, Environment Correspondent

WASHINGTON - The Arctic ice cap is melting much faster than expected and is now about 30 years ahead of predictions made by the Intergovernmental Panel on Climate Change, a US ice expert said on Tuesday.

This means the ocean at the top of the world could be free or nearly free of summer ice by 2020, three decades sooner than the global panel's gloomiest forecast of 2050.

No ice on the Arctic Ocean during summer would be a major spur to global warming, said Ted Scambos, a glaciologist at the National Snow and Ice Center in Colorado.

"Right now ... the Arctic helps keep the Earth cool," Scambos said in a telephone interview. "Without that Arctic ice, or with much less of it, the Earth will warm much faster." That is because the ice reflects light and heat; when it is gone, the much darker land or sea will absorb more light and heat, making it more difficult for the planet to cool down, even in winter, he said.

Scambos and co-authors of the study, published in the journal Geophysical Research Letters, used satellite data and visual confirmation of Arctic ice to reach their conclusions, a far different picture than that obtained from computer models used by the scientists of the intergovernmental panel.

"The IPCC report was very careful, very thorough and cautious, so they erred on the side of what would certainly occur as opposed to what might occur," Scambos said in a telephone interview.

ICE-FREE SUMMER

The wide possibility of what might occur included a much later melt up north, or a much earlier one, Scambos said.

"It appears we're on pace about 30 years earlier than expected to reach a state where we don't have sea ice or at least not very much in late summer in the Arctic Ocean," he said.

He discounted the notion that the sharp warming trend in the Arctic might be due to natural climate cycles.

"There aren't many periods in history that are this dramatic in terms of natural variability," Scambos said.

He said he had no doubt that this was caused in large part by greenhouse gases in the atmosphere, which he said was the only thing capable of changing Earth on such a large scale over so many latitudes.

Asked what could fix the problem -- the topic of a new report by the intergovernmental panel to be released on Friday in Bangkok -- Scambos said a large volcanic eruption might hold Arctic ice melting at bay for a few years.

But he saw a continued warm-up as inevitable in the coming decades. "Long-term and for the next 50 years, I think even the new report will agree that we're in for quite a bit of warming," Scambos said. "We just barely now, I think, have enough time and enough collective will to be able to get through this century in good shape, but it means we have to start acting now and in a big way."
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