Greenhouse gases highest for 800,000 years

By Alister Doyle, Environment Correspondent

OSLO (Reuters) - Greenhouse gases are at higher levels in the atmosphere than at any time in at least 800,000 years, according to a study of Antarctic ice on Wednesday that extends evidence that mankind is disrupting the climate.

Carbon dioxide and methane trapped in tiny bubbles of air in ancient ice down to 3,200 meters (10,500 ft) below the surface of Antarctica add 150,000 years of data to climate records stretching back 650,000 years from shallower ice drilling.

"We can firmly say that today's concentrations of carbon dioxide and methane are 28 and 124 percent higher respectively than at any time during the last 800,000 years," said Thomas Stocker, an author of the report at the University of Berne.

Before the Industrial Revolution, levels of greenhouse gases were guided mainly by long-term shifts in the earth's orbit around the sun that have plunged the planet into ice ages and back again eight times in the past 800,000 years.

The U.N. Climate Panel last year blamed human activities, led by burning of fossil fuels that release heat-trapping gases, for modern global warming that may disrupt water and food supplies with ever more droughts, floods and heatwaves.

"The driving forces now are very much different from the driving forces in the past when there was only natural variation," Stocker told Reuters of the study in the journal Nature by scientists in Switzerland, France and Germany.

The experts, working on the European Project for Ice Coring in Antarctica, drilled down almost to bedrock in Antarctica. They recovered layers of ice formed by compressed snow, which can be counted much like the rings on trees.

DEEPER ICE