Arctic warming 'points to ice-free summers'

The Arctic is warming at a faster rate than the rest of the world, according to research that suggests the continent may never recover from global warming.

Matthew Moore, The Telegraph 16 Dec 08;

Scientists have detected that autumn air temperatures in the region are higher than expected, due to a phenomena called Arctic amplification under which increased melting of sea ice in the summer accumulates heat in the ocean.

Climate-change researchers had not expected to observe Arctic amplification for 10 to 15 years, suggesting that global warming is more advanced that previously thought.

A study from the American Geophysical Union in San Francisco will show that the phenomena has been taking place for five years and will likely intensify in the future, raising the prospect of ice-free summers in the Arctic.

In parts of the region, such as the Beaufort Sea north of Alaska, air temperatures were 7C higher than normal for the season.

Julienne Stroeve of the US National Snow and Ice Data Centre, who jointly led the study, told The Independent: "The warming climate is leading to more open water in the Arctic Ocean. As these open water areas develop through spring and summer, they absorb most of the sun's energy, leading to ocean warming.

"In the autumn, as the sun sets in the Arctic, most of the heat that is gained in the ocean during summer is released back into the atmosphere. It is this heat-release back to the atmosphere that gives us Arctic amplification."

The Arctic had been predicted to see ice-free summers by 2070, but many scientists are now predicting it could happen within the next 20 years, according to the newspaper.

Over 2T tons of ice melted in arctic since '03
Yahoo News 16 Dec 08;

WASHINGTON – More than 2 trillion tons of land ice in Greenland, Antarctica and Alaska have melted since 2003, according to new NASA satellite data that show the latest signs of what scientists say is global warming.

More than half of the loss of landlocked ice in the past five years has occurred in Greenland, based on measurements of ice weight by NASA's GRACE satellite, said NASA geophysicist Scott Luthcke. The water melting from Greenland in the past five years would fill up about 11 Chesapeake Bays, he said, and the Greenland melt seems to be accelerating.

NASA scientists planned to present their findings Thursday at the American Geophysical Union conference in San Francisco. Luthcke said Greenland figures for the summer of 2008 aren't complete yet, but this year's ice loss, while still significant, won't be as severe as 2007.

The news was better for Alaska. After a precipitous drop in 2005, land ice increased slightly in 2008 because of large winter snowfalls, Luthcke said. Since 2003, when the NASA satellite started taking measurements, Alaska has lost 400 billion tons of land ice.

In assessing climate change, scientists generally look at several years to determine the overall trend.

Melting of land ice, unlike sea ice, increases sea levels very slightly. In the 1990s, Greenland didn't add to world sea level rise; now that island is adding about half a millimeter of sea level rise a year, NASA ice scientist Jay Zwally said in a telephone interview from the conference.

Between Greenland, Antarctica and Alaska, melting land ice has raised global sea levels about one-fifth of an inch in the past five years, Luthcke said. Sea levels also rise from water expanding as it warms.

Other research, being presented this week at the geophysical meeting point to more melting concerns from global warming, especially with sea ice.

"It's not getting better; it's continuing to show strong signs of warming and amplification," Zwally said. "There's no reversal taking place."

Scientists studying sea ice will announce that parts of the Arctic north of Alaska were 9 to 10 degrees warmer this past fall, a strong early indication of what researchers call the Arctic amplification effect. That's when the Arctic warms faster than predicted, and warming there is accelerating faster than elsewhere on the globe.

As sea ice melts, the Arctic waters absorb more heat in the summer, having lost the reflective powers of vast packs of white ice. That absorbed heat is released into the air in the fall. That has led to autumn temperatures in the last several years that are six to 10 degrees warmer than they were in the 1980s, said research scientist Julienne Stroeve at the National Snow and Ice Data Center in Boulder, Colo.

That's a strong and early impact of global warming, she said.

"The pace of change is starting to outstrip our ability to keep up with it, in terms of our understanding of it," said Mark Serreze, senior scientist at the National Snow and Ice Data Center in Boulder, Colo., a co-author of the Arctic amplification study.

Two other studies coming out at the conference assess how Arctic thawing is releasing methane — the second most potent greenhouse gas. One study shows that the loss of sea ice warms the water, which warms the permafrost on nearby land in Alaska, thus producing methane, Stroeve says.

A second study suggests even larger amounts of frozen methane are trapped in lakebeds and sea bottoms around Siberia and they are starting to bubble to the surface in some spots in alarming amounts, said Igor Semiletov, a professor at the University of Alaska in Fairbanks. In late summer, Semiletov found methane bubbling up from parts of the East Siberian Sea and Laptev Sea at levels that were 10 times higher than they were in the mid-1990s, he said based on a study this summer.

The amounts of methane in the region could dramatically increase global warming if they get released, he said.

That, Semiletov said, "should alarm people."

Arctic Ice Volume Lowest Ever as Globe Warms: UN
Robert Evans, PlanetArk 17 Dec 08;

GENEVA - Ice volume around the Arctic region hit the lowest level ever recorded this year as climate extremes brought death and devastation to many parts of the world, the U.N. weather agency WMO said on Tuesday.

Although the world's average temperature in 2008 was, at 14.3 degrees Celsius (57.7 degrees Fahrenheit), by a fraction of a degree the coolest so far this century, the direction toward a warmer climate remained steady, it reported.

"What is happening in the Arctic is one of the key indicators of global warming," Michel Jarraud, Secretary General of the World Meteorological Organization (WMO), said. "The overall trend is still upwards."

A report presented by Jarraud at a news conference showed Arctic ice cover dropping to its second lowest extent during this year's melt season since satellite measuring began in 1979.

However, the Geneva-based agency said, "because ice was thinner in 2008, overall ice volume was less than in any other year." It added: "The season strongly reinforced the 30-year downward trend in the extent of Arctic Sea ice."

The dramatic collapse of a quarter of ancient ice shelves on Canada's Ellesmere Island in the north of the Arctic Ocean added to earlier meltdowns, reducing cover in the region from 9,000 square km (3,500 sq miles) a century ago to just 1,000 sq kms.

The WMO said the slight slowdown in warming this year, an increase of 0.31C over the 14C of the base period 1961-90, against an average 0.43C for 2001-2007, was due to a moderate-to-strong La Nina in the Pacific in late 2007.

"This decade is almost 0.2 degrees (Celsius) warmer compared to the previous decade. We have to look at it in that way, comparing decades not years," Peter Stott, a climate scientist at Britain's Hadley Center, which provided data for the WMO report, told Reuters in London.

LA NINA, EL NINO

La Nina is a periodic weather pattern that develops when Pacific sea water cools. It alternates irregularly with the related El Nino -- when the Pacific warms up -- and both affect the climate all round the world.

The WMO report was based on statistics and analyses compiled by weather services among its 188 member countries and specialist research institutions, including government-backed bodies in the United States and Britain.

"Climate extremes, including devastating floods, severe and persistent droughts, snow storms, heat waves and cold waves were recorded in many parts of the world," the agency said. In many of these, hundreds or even thousands of people died.

Among the disasters was Cyclone Nargis, which killed some 78,000 in Myanmar's southern delta region in early May. In the western Atlantic and Caribbean there were 16 major tropical storms, eight of which developed into hurricanes.

In an average year, there are 11 storms of which six become hurricanes and two become major hurricanes. In 2008, five major hurricanes developed, and for the first time on record six tropical storms in a row made landfall in the United States.

The WMO says the 10 hottest years since global records were first kept in 1850 have all been since 1997, with the warmest at 14.79 C in 2005. Countries have been struggling for years to reach agreement on how to halt the trend.

This month a two-week meeting of leaders in Poznan, Poland, called to prepare a treaty for late 2009 seemed to falter amid rows between rich and poor nations and what some climate campaigners say was lack of will to get things done.

-- Additional reporting by Gerard Wynn and Michael Szabo in London

(Editing by Stephanie Nebehay and Michael Roddy)

Has the Arctic melt passed the point of no return?
Steve Connor, The Independent 16 Dec 08;

Scientists have found the first unequivocal evidence that the Arctic region is warming at a faster rate than the rest of the world at least a decade before it was predicted to happen.

Climate-change researchers have found that air temperatures in the region are higher than would be normally expected during the autumn because the increased melting of the summer Arctic sea ice is accumulating heat in the ocean. The phenomenon, known as Arctic amplification, was not expected to be seen for at least another 10 or 15 years and the findings will further raise concerns that the Arctic has already passed the climatic tipping-point towards ice-free summers, beyond which it may not recover.

The Arctic is considered one of the most sensitive regions in terms of climate change and its transition to another climatic state will have a direct impact on other parts of the northern hemisphere, as well more indirect effects around the world.

Although researchers have documented a catastrophic loss of sea ice during the summer months over the past 20 years, they have not until now detected the definitive temperature signal that they could link with greenhouse-gas emissions.

However, in a study to be presented later today to the annual meeting of the American Geophysical Union in San Francisco, scientists will show that Arctic amplification has been under way for the past five years, and it will continue to intensify Arctic warming for the foreseeable future.

Computer models of the global climate have for years suggested the Arctic will warm at a faster rate than the rest of the world due to Arctic amplification but many scientists believed this effect would only become measurable in the coming decades.

However, a study by scientists from the US National Snow and Ice Data Centre (NSIDC) in Colorado has found that amplification is already showing up as a marked increase in surface air temperatures within the Arctic region during the autumn period, when the sea ice begins to reform after the summer melting period.

Julienne Stroeve, of the NSIDC, who led the study with her colleague Mark Serreze, said that autumn air temperatures this year and in recent years have been anomalously high. The Arctic Ocean warmed more than usual because heat from the sun was absorbed more easily by the dark areas of open water compared to the highly reflective surface of a frozen sea. "Autumn 2008 saw very strong surface temperature anomalies over the areas where the sea ice was lost," Dr Stroeve told The Independent ahead of her presentation today.

"The observed autumn warming that we've seen over the Arctic Ocean, not just this year but over the past five years or so, represents Arctic amplification, the notion that rises in surface air temperatures in response to increased atmospheric greenhouse gas concentrations will be larger in the Arctic than elsewhere over the globe," she said. "The warming climate is leading to more open water in the Arctic Ocean. As these open water areas develop through spring and summer, they absorb most of the sun's energy, leading to ocean warming.

"In autumn, as the sun sets in the Arctic, most of the heat that was gained in the ocean during summer is released back to the atmosphere, acting to warm the atmosphere. It is this heat-release back to the atmosphere that gives us Arctic amplification."

Temperature readings for this October were significantly higher than normal across the entire Arctic region – between 3C and 5C above average – but some areas were dramatically higher. In the Beaufort Sea, north of Alaska, for instance, near-surface air temperatures were more than 7C higher than normal for this time of year. The scientists believe the only reasonable explanation for such high autumn readings is that the ocean heat accumulated during the summer because of the loss of sea ice is being released back into the atmosphere from the sea before winter sea ice has chance to reform.

"One of the reasons we focus on Arctic amplification is that it is a good test of greenhouse warming theory. Even our earliest climate models were telling us that we should see this Arctic amplification emerge as we lose the summer ice cover," Dr Stroeve said. "This is exactly what we are not starting to see in the observations. Simply put, it's a case of we hate to say we told you so, but we did," she added.

Computer models have also predicted totally ice-free summers in the Arctic by 2070, but many scientists now believe that the first ice-free summer could occur far earlier than this, perhaps within the next 20 years.