Correction at 3:30 p.m. PST Thursday: Blame my Rust Belt ignorance. The Ohio river that burned is the Cuyahoga.
The retreat of the Jakobshavn Glacier on western Greenland is accelerating, Thompson said. Shown here are lines indicating the location of the end of the glacier starting in 1850 at the far left. The furthest yellow line on the right is 2000, and the two red lines are 2003 and, at far right, 2005.
(Credit: Lonnie Thompson/Ohio State University)SAN FRANCISCO--I've been spending some time at the the American Geophysical Union conference here, and I've had a recurring thought: When it comes to apocalyptic predictions, geophysicists have the Book of Revelations beat, hands down.
Sometime in the last few years, the idea that global warming is a reality and that it's caused in large measure by people has finally started sinking in. But perhaps because of the remaining skepticism, and more likely because of the fascinating research involved, scientists just can't leave the issue alone.
Global warming has been a major theme among the 14,500 scientists who have converged here for the 40th AGU conference. Seemingly, they can't get enough of it: A year after former Vice President Al Gore addressed conference attendees during the height of hype around his Inconvenient Truth documentary, organizers again gave the stage to an articulate speaker on the issue. This time it was Lonnie Thompson, an Ohio State University scientist who has spent innumerable hours drilling into icecaps at the world's highest elevations.
Lonnie Thompson at AGU
(Credit: Stephen Shankland/CNET News.com)Global warming, a decades-old idea that posits certain greenhouse gases will keep heat from escaping into space, has moved gradually from a prediction to a measurable phenomenon. But for those who are inclined to feel comfort that scientists got it right, Thompson had sobering words on Wednesday evening: the pace of glacial melting is accelerating, and scientists don't have a handle on the new patterns.
"We're in unfamiliar territory," Thompson said. "The observed rapid changes in Greenland and Antarctica are not predicted. What we're seeing is fast glacier flow."
Thompson uses yaks to carry back each one of hundreds of six-foot ice core samples retrieved from holes drilled in glaciers.
(Credit: Lonnie Thompson/Ohio State University)Take the Jacobshavn Ice Stream, a glacier on the west side of Greenland that drains about 6.5 percent of the continent's massive ice sheet. Between 2000 and 2003, its rate of retreat nearly doubled. Scientists expected a slow and linear response to global warming, but instead the response has been fast and accelerating. Another example is the Qori Kalis Glacier in Peru, whose initial retreat rate around 1991 was about 6 meters per year but now is 60 meters per year.
"It's not just retreating. It's an exponential increase," he said.
Humanity has a lousy track record dealing with environmental crises before they become severe, he said, pointing as an example to Ohio's famously polluted Cuyahoga River.
"When did we do anything about that river? When it caught on fire," he said. "We've cleaned it up. Now there are walleye and pike in it. It wasn't that we couldn't do it; it was that we didn't have the political will to do it."
Compared to some crises, though, global warming poses long-term challenges because greenhouse gases stay in the atmosphere 70 to 120 years after being emitted, he said.
This year, melting split the Furtwangler Glacier on Africa's Mt. Kilamanjaro into two halves.
(Credit: Lonnie Thompson/Ohio State University)Glaciers are only one reflection of overall climate trends, but Thompson believes they're an important one--especially the ones he's specialized in studying, those growing at the tops of high mountains in central latitudes rather than the vast expanses in the Arctic and Antarctic regions.
"Glaciers, especially tropical glaciers, are the canaries in the coal mine for our global climate system," he said.
In his research, Thompson has spent 840 days above 18,000 feet, setting up camps and drilling out cores of ice from the glaciers. The ice cores record in tiny air bubbles volcanic activity and greenhouse gas levels; each year has its own layer that can be dated by characteristic patterns of dust deposition and by wet and dry seasons.
The ice core records are disappearing along with the glaciers, though. Several he's examined, for example, show evidence of above-ground thermonuclear bomb tests from the Soviet Union in the 1960s and the United States in the 1950s. But there's no evidence of either on the Naimona'nyi Glacier on the Tibetan Plateau.
"These glaciers are wasting from the surface down," Thompson said.
This graphic shows in red the area of arctic ice that was present in the summer of 1980 but missing this summer. At lower right is the equivalent surface area in terms of the size of the United States.
(Credit: Credit: Don Perovich, U.S. Army Cold Regions Research and Engineering Laboratory)SAN FRANCISCO--Warmth may not be an attribute you associate with a place where the sun doesn't shine in the winter and the sea freezes over, but all things are relative. And compared to earlier years, the Arctic was downright sweltering this year.
According to new research presented here at the the American Geophysical Union conference, the Arctic Ocean reached record high temperatures, arctic ice diminished to a record low, and ice melted on Greenland for a record number of days.
"In 2007, we had off-the-charts warming" of the Arctic Sea in the summer, said Mike Steele, an oceanographer with the Polar Science Center at the University of Washington.
Specifically, he said the Arctic Sea surface temperature was 3.5 degrees Celsius (6.3 degrees Fahrenheit) warmer than the 100-year historical average and 1.5 degrees Celsius (2.7 degrees Fahrenheit) warmer than the historical maximum. Two factors were at play in the heating: the sun and, to a lesser degree, warmer ocean currents, he said. In one area north of Russia, temperatures were 5 degrees Celsius (9 degrees Fahrenheit) above average.
This comparison shows the 'off-the-charts' relative warmth of the Arctic Ocean in the summer of 2007.
(Credit: Mike Steele, University of Washington)There's a feedback loop that connects the ocean temperature and the melting of sea ice. "The ocean absorbs heat, which melts the ice, which means there's more open ocean, which means more heat is absorbed," said Don Perovich, an arctic ice scientist at the U.S. Army Cold Regions Research and Engineering Laboratory. "It's a classic positive feedback."
It's no surprise that the arctic ice is shrinking. But the new data gives a specific measurement for how much is gone.
Between September 1980 and September 2007, the Arctic Sea ice dropped from 7.8 million square kilometers to 4.2 million square kilometers, Perovich said. "You can see the Northwest Passage, the shortcut across the top of the world, was ice-free at the end of the summer."
For comparison, the area of ice is the same as all the states east of the Mississippi River and a broad swath of those to its west, he said.
The math behind the feedback loop involves a property called albedo, which measures the fraction of sunlight that's reflected. The albedo of ice is about 85 percent, compared to 7 percent for the ocean.
What got the feedback loop started is a subject of some debate. "The ice-albedo feedback needs a trigger," Perovich said.
Culprits include a surge of warm water from the Pacific Ocean and anomalous winds that may have pushed ice to create more open ocean. And global warming in general means warmer air, which means a later start to winter ice freezing and less freezing when it does begin, Steele said.
Steele estimates that 2007's warm summer will reduce ice thickness by about a meter, Steele added.
With thinner ice, it's easier to start the feedback loop again. "The ice is more vulnerable to a short-term wind event," Perovich said.
Greenland, too, is showing signs of warming.
Red areas here show areas of Greenland where ice melting in 2007 lasted unusually long--the darkest being 30 days more than the average of the years from 1988 through 2006.
(Credit: Credit Marco Tedesco, University of Maryland)"2007 set a new record, with melting occurring for 25 to 30 days longer than the average of 1980 to 2006," said Marco Tedesco of the University of Maryland.
The rate of increase in melting since 1988 is about 19,000 additional square kilometers each year, about 1.5 times the size of Maryland, Tedesco said.
Greenland, too, has an albedo-related feedback loop. When less snow falls, older and darker snow is more exposed, and this older snow absorbs more heat, Tedesco said. That albedo effect, combined with unusually high temperatures, were responsible for the increased melting, Tedesco said.
Arctic Sea ice melting doesn't increase sea level, but Greenland is another matter: all its water is on land today, so thawing will increase oceans.
SAN FRANCISCO--Researchers have linked global climate change to a tripling in the frequency of large fires in major forests of Alaska and Canada.
Black spruce forests cover about 2.7 million square kilometers in Canada and Alaska--about a third of the area of the lower 48 states of the U.S., and fire records date back to the 1950s. Beginning around 1987, the rate that large wildfires struck the forest jumped from about once every 10 years to once every 3 years, said Eric Kasischke of the University of Maryland at College Park, speaking at the American Geophysical Union conference here Monday.
"We've seen an increase in the number of very large arboreal fires," Kasischke said. (He defines a large fire as one that burns more than 1 percent of the land area in a particular region, such as Alaska's interior.)
There are two links to the gradually warming climate, he said. First, the fires increasingly show up in the fall, when soils are driest and fires therefore are more severe, he said.
Second, the fires are burning deeper into the soil, a significant change given that these northern forests have a thick layer of biological material, typically about 10 inches deep.
"The fires that change the ecosystem the most are occurring more frequently," he said. He predicted that the gradual warming will mean black spruce forests gradually will be replaced by aspen, birch, lodgepole pine, and jack pine forests. In addition, when the organic layer burns, permafrost below no longer is as well insulated.
The deep-burning fires are something of a vicious cycle, too, from a global warming perspective. With the thick layer of biomass, the black spruce forests typically have about 50 tons of carbon per hectare--or about 20 tons per acre--where ordinary U.S. forests have only about a fifth that. When burned, that carbon becomes carbon dioxide, the dominant greenhouse gas culprit in global warming.
The deep burn releases enough carbon dioxide that "you can detect the signal in trace gas emissions," Kasischke said.
A 10-square-mile pack of jellyfish wiped out a 100,000-fish salmon farm in Northern Ireland, the Associated Press reported Wednesday.
The billions of jellyfish, piled densely in a 35-foot-deep layer, did in the fish through stings and stress, according to John Russell, managing director of Northern Salmon.
The Pelagia nocticula species, or "mauve stinger," ordinarily is found in warmer waters such as the Mediterranean Sea. Scientists pointed to the presence of the jellyfish, rarely seen that far north, as evidence of global warming.
All of the fish, worth $2 million, are dead or dying and, absent government aid, the farm likely will go out of business, Russell said.
- prev
- 1
- next
