Greenhouse Gases Highest In 8 Lakh Years

GREENHOUSE GASES HIGHEST IN 8 LAKH YEARS

Proof That Humankind Is Disrupting Climate

Oslo: Greenhouse gases are at higher levels in the atmosphere than at any time in at least 8, 00,000 years, according to a study of Antarctic ice that extends evidence that humankind is disrupting the climate.

Carbon dioxide and methane trapped in tiny bubbles of air in ancient ice down to 3,200 metres below the surface of Antarctic 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% higher respectively than at any time during the last 8 lakh years,” said Thomas Stocker, an author of the report at the University of Berne on Wednesday. Before the Industrial Revolution, levels of greenhouse gases were guided mainly by long-term shifts in the earth’s orbits around the sun that have plunged the planet into eight times in the past 8,00,000 years.

The UN 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 even more droughts, floods and heat waves.

“The driving forces now are very much different from the driving forces in the past when there was an only natural variation,” Stocker said of the study in the journal Nature by scientists in Switzerland, France and Germany. The experts, working on the European Project for Ice Corning 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. Stocker said Chinese and Australian scientists were examining possibilities for drilling in parts of Antarctica with even deeper ice, in some places 4,500 metres thick, that could yield atmospheric records dating back 1.5 million years.

The study also found big naturals shifts in carbon dioxide levels. “We find very conspicuous natural oscillations of carbon dioxide 770,000 years ago that bear the fingerprint of abrupt climate change during ice ages,” Stocker said.

And the Nature report also set a new record low for carbon dioxide at 172 parts per million(ppm) in the atmosphere about 667,000 years ago, about 10 ppm below the previous known low and giving an ancient natural range of 172 to about 300 ppm. The study suggested that the low might be a sign that the oceans once soaked up more carbon dioxide. Carbon dioxide levels are now at about 380 ppm.