WASHINGTON — Currents flowing like rivers from pole to pole and from ocean to ocean help keep the Earth's weather in a steady state, but the buildup of greenhouse gases in the atmosphere is threatening this circulation and could dump Europe into a deep freeze, a researcher says.
The dependable pattern of ocean circulation is a key factor in controlling the Earth's weather and keeping it predictable, says Wallace S. Broecker of the Lamont-Doherty Earth Observatory of Columbia University in Palisades, N.Y.
But this has only been true for the last 8,000 years. Before that, ocean currents altered about every 1,000 years and scrambled the Earth's climate, Broecker says in a study to be published today in the journal Science.
"We live in a climate system that can jump abruptly from one state to another," Broecker says. By dumping into the atmosphere huge amounts of greenhouse gases, such as carbon dioxide from the burning of fossil fuels, "we are conducting an experiment that could have devastating effects," he adds.
"We're playing with an angry beast--a climate system that has been shown to be very sensitive," he says.
The study findings come as representatives from more than 140 nations prepare to gather in Kyoto, Japan, next week in hopes of forging an agreement committing industrial nations to specific reductions of greenhouse gases, especially carbon dioxide from burning fossil fuels.
Broecker says studies of ice cores that date back 110,000 years show that about once a millennium the Earth's climate abruptly changes and within 10 to 20 years can cause such things as increased glaciers, halting of rainfall or crippling declines in temperature.
Ocean currents are controlled by the temperature and salt content of the water, according to the researcher. Cold, salty water is heavy and drops to the ocean bottom, while warm, fresh water rises.
This creates what Broecker calls a "conveyor" current that spans the globe. Cold, salty water in the North Atlantic sinks, working like a plunger to drive an ocean current from near North America to Europe. Warm surface waters borne by this current help keep Europe's climate mild.
Without the current, Broecker says, "Europe would be a deep freeze" with average winter temperatures dropping by 20 degrees Fahrenheit or more. The climate of Dublin or London would be like that of Spitsbergen, Norway, which is 600 miles north of the Arctic Circle, he said.
