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Glacial-melt rate quickens, accelerating sea changes
The Washington Post
WASHINGTON — Greenland's glaciers are melting into the sea twice as fast as previously believed, the result of a warming trend that renders obsolete predictions of how quickly the Earth's oceans will rise in the next century, scientists said Thursday.
The new data come from satellite imagery and give fresh urgency to worries about the role of human activity in global warming. The Greenland data are mirrored by findings from Bolivia to the Himalayas, scientists said, noting that sea-level rise threatens widespread flooding and severe storm damage in low-lying areas worldwide.
The scientists said they did not understand the mechanism causing glaciers to flow and melt more rapidly, but they said the changes in Greenland were unambiguous — and accelerating: In 1996, the amount of water produced by melting ice in Greenland was about 90 times the amount consumed by Los Angeles in a year. Last year, the melted ice amounted to 225 times the volume of water that Los Angeles uses annually.
"We are witnessing enormous changes, and it will take some time before we understand how it happened, although it is clearly a result of warming around the glaciers," said Eric Rignot, a scientist at the California Institute of Technology's Jet Propulsion Lab.
The Greenland study is the latest of several in recent months that have found evidence that rising temperatures are affecting Earth's ice sheets and such things as plant and animal habitats, the health of coral reefs, hurricane severity and droughts and globe-girdling currents that drive regional climates.
The ice sheets in Greenland and Antarctica are among the largest reservoirs of fresh water on Earth, and their fate is expected to be a major factor in determining how much Earth's oceans will rise. Rignot and University of Kansas scientist Pannir Kanagaratnam, who published their findings Thursday in the journal Science, declined to guess how much the faster melting would raise sea levels but said current estimates of about 20 inches in the next century are probably too low.
While sea-level increases of a few feet may not sound like much, they could have profound consequences on flood-prone countries such as Bangladesh and trigger severe weather around the world.
The study also highlights how seemingly small changes in temperature can have massive effects. Where glaciers in Greenland were once retreating around four miles a year, they are now moving twice as fast. While it is possible that increased precipitation in northern Greenland is compensating for the melting in the south, the scientists said that is unlikely.
At a news conference Thursday organized by the American Association for the Advancement of Science at its annual meeting in St. Louis, glacier scientists Vladimir Aizen from the University of Idaho and Gino Casassa of Chile's Centro de Estudios Científicos said they were seeing the same thing happen to glaciers in the Himalayas and in South America.
Most climate scientists think a major cause for Earth's warming climate is increased emissions of greenhouse gases as a result of burning fossil fuels, largely in wealthy, industrialized nations such as the United States and in Western Europe, but increasingly in rapidly developing nations such as China and India as well. Carbon dioxide and several other gases trap the sun's heat and raise atmospheric temperature.
"This study underscores the need to take swift, meaningful actions at home and abroad to address climate change," said Vicki Arroyo, director of policy analysis at the Pew Center on Global Climate Change.
"This is the kind of study that should make people stay awake at night wondering what we're doing to the climate, how we're shaping the planet for future generations and, especially, what we can do about it."
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