C[O.sup.2] levels in the atmosphere are higher than at any time in 650,000 years, according to ice cores drilled by European scientists in Antarctica.
Gas bubbles trapped as the ice formed yield important evidence of the temperature and mixture of gases present in the atmosphere at that time.
Led by Thomas Stocker of the University of Bern, scientists with the European Project for Ice Coring in Antarctica say their finding is strong evidence that humans have changed the climate more in the past 200 years than nature did over millennia.
"We are out of the natural range," Stocker said. "We find that C[O.sup.2] is about 30 per cent higher than at any time, and methane, 130 per cent higher than at any time."
And the rates of increase are "absolutely exceptional: for C[O.sup.2], 200 times faster than at any time in the last 650,000 years," he added.
In the past five years, the average global temperature has risen by 0.2[degrees]C-100 times higher than normal for such a period.
Greenhouse sceptics argue that human activities like the...