Study finds Alaska glaciers melting at higher rate

Researchers surveyed volume and area changes across Alaska's glacier regions by plane and found the glaciers' melt rate was on the rise.

(CNN) -- A new study indicates that glaciers in Alaska are melting faster than previously thought, providing further evidence of global warming, researchers said Thursday.

Scientists have long warned that global warming -- when heat-trapping gases force atmospheric temperatures to rise -- could eventually raise sea levels to a dangerous point by melting ice sheets and glaciers.

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"The whole issue of global climate change is important to everyone," said glacier expert Anthony Arendt of the University of Alaska at Fairbanks. "The whole issue of sea-level change affects people who live near the coast quite directly. Just small changes in sea level can cause very large incursions of water up along the coast and can destroy valuable property there. It can move people away from their homes."

Arendt and his colleagues used a technology called laser altimetry to measure volume changes of 67 Alaskan glaciers over four decades.

EXTRA INFORMATION Measuring the meltdown

"Glaciers in Alaska seem to be thinning from the mid-1950s to the mid-1990s," said Arendt, adding that the thinning rate has about doubled between the mid-1990s and 2001.

"We know that the climate has had to change for that to happen," he said. "Whether or not these changes in climate are due to human influences, that's not for us to say, but it's possible that it is linked to a larger-scale change in global climate caused by human activity."

A panel of scientists that regularly reports to the United Nations on global warming issues has projected that sea level will rise between three inches and about two-and-a-half feet during this century. But glaciers melting faster than expected could increase that projection.

The study found that the Alaskan glaciers were thinning enough to produce a sea-level rise of about .14 millimeters per year -- melting almost twice as fast as the Greenland ice sheet, the researchers said.

The survey, published in the journal Science, relied on an airborne laser and a satellite-based global positioning system to plot the glaciers' altitudes and calculate their volume. Comparisons were then made with topographic maps from years before the 1990-technology was developed, to extrapolate melting rates back to the 1950s.

Glaciers in Alaska and neighboring Canada cover about 13 percent of the mountain glacier area on Earth.

The Environmental Protection Agency says the Earth's temperature has risen about 1 degree Fahrenheit during the past 100 years, most likely because of global warming.

"Human activities have altered the chemical composition of the atmosphere through the buildup of greenhouse gases – primarily carbon dioxide, methane, and nitrous oxide," says a definition posted on the EPA Web site. "The heat-trapping property of these gases is undisputed although uncertainties exist about exactly how Earth's climate responds to them."