An ice age that gripped the Earth for thousands of years ended abruptly when temperatures soared, according to new findings that suggest the world's climate can change in just a few decades.
The study prompts fresh concerns that climate change from global warming could happen suddenly.
Jeffrey P. Severinghaus of the Scripps Institution of Oceanography said that a new method of analyzing gases trapped in Greenland ice shows that the air temperatures warmed rapidly at the end of the last ice age--about 15,000 years ago.
"There was a 16 degree abrupt warming at the end of the last ice age," said Severinghaus, lead author of a study published Friday in the journal Science. "It happened within just a couple of decades. The old idea was that the temperature would change over a thousand years.
Severinghaus said the rapid temperature increase may have been touched off by a surge in warm currents in the Atlantic Ocean that brought a melting trend to the vast ice sheet covering the Northern Hemisphere. It still took hundreds of years for the ice to recede, but the start of the great thaw was much more sudden than scientists had once thought.
This suggests, Severinghaus said, that the Earth's climate is "tippy"--stable for long periods, but subject to sudden change under the right conditions.
Pieter P. Tans, a scientist at the National Oceanographic and Atmospheric Administration, said that "both the rapidity and the magnitude of the temperature change is surprising."
But scientific caution demands "another piece of evidence to support it," he said.
Many experts have predicted that an increase in greenhouse gases, such as carbon dioxide, could cause a gradual global warming, with temperatures rising slowly over many decades.
But Severinghaus said the Greenland ice core study suggests that such changes in the Earth's climate may not be smooth, but sudden.
"We might do well to expect surprisesÂ…," he said. "We know that over the next 100 years the Earth will probably warm because of the greenhouse effect and there is a remote possibility that we might trigger one of these abrupt climate changes."
The greenhouse effect is global warming caused by the build up in the atmosphere of manmade carbon dioxide and other gases that trap the sun's heat. A steady rise in carbon dioxide that has been detected since 1850 is thought to be from increased burning of fossil fuels, such as gasoline and coal.