Rapid Swings

Scientists See Evidence of Rapid Climate Change
MSNBC Online, October 28, 1999

In a study that may sound a warning about global warming, researchers have found evidence that the world's climate can change suddenly, almost like a thermostat that clicks from cold to hot. A new technique for analyzing gases trapped in Greenland glaciers shows that an ice age that gripped the Earth for thousands of years ended abruptly 15,000 years ago when the average air temperatures soared. "There was a 16-degree abrupt warming at the end of the last ice age," said Jeffrey P. Severinghaus of the Scripps Institution of Oceanography, lead author of a study to be 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. But we found it was much faster."

Change in Water Temperature

Severinghaus said the rapid rise in air temperature in Greenland 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 that covered 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" - prone to be stable for long periods, but then suddenly change when the conditions are right. This raises a red flag of caution for the effect of greenhouse gases on global warming.