Gas May Have Spurred Ancient Global Warming - Nature
Author: Alister Doyle, Environment Correspondent
The apparent release of hydrocarbons from subsea rocks in the Eocene epoch might also bolster theories that spasms of volcanic activity could have triggered extinctions like the demise of the dinosaurs 10 million years before the Eocene.
In an article in the science journal Nature, Norwegian researchers said they had found traces of thousands of hydrothermal vents in lava off Norway that could have been the source of a rise in greenhouse gases 55 million years ago.
Until now, scientists have been at a loss to explain the trigger for a 5-10 Celsius (10-20F) global warming over about 10,000 years in the Eocene -- a blink in geological time.
"We think that magma heated sediments containing organic material and led to an explosive release of gases," said Henrik Svensen, a researcher at the University of Oslo and main author of the article.
"It's like burning a pizza and creating a lot of greenhouse gas in your stove," he told Reuters. Some of the craters were 10 km (six miles) across in the Voering and Moere basins in the North Atlantic off what is now Norway.
Some plants and animals, especially in the seas, were wiped out by the Eocene temperature spike. "But it's not one of the major global extinction events," he said.
The scientists said the annual rate of modern human emissions of greenhouse gases to the atmosphere in the 1990s -- from fossil fuels burned in cars, factories and power plants -- was 35-360 times as fast as the pace of the Eocene gas buildup.
"We can cause the same amount of global warming ourselves in a few hundred years at current rates," Svensen said. Scientists say that gases linked to human activity could bring disaster with more storms, floods and higher sea levels.
The Eocene global warming theory outlined in Nature bolsters the idea that a buildup of gases can disrupt the climate, as forecast by U.N. models. A U.N. panel of scientists has predicted a 1.4-5.8 Celsius rise in temperatures by 2100.
Gerald Dickens of Rice University, Texas, wrote in Nature that the Eocene warming should be studied more as "an intriguing but imperfect analog of current fossil-fuel emissions."
During the Eocene, mammals strengthened their grip on the planet after the extinction of the dinosaurs. Creatures ranged from horse-like animals as small as dogs to a spiny relative of the hedgehog that apparently hopped like a rabbit.
Much of the gas released was apparently methane, a major component of natural gas and the second-biggest contributor to global warming behind carbon dioxide. The U.N.'s stalled 1997 Kyoto protocol seeks to limit emissions despite a U.S. pullout.
Svensen said the theory of Eocene warming might bolster the idea that volcanoes were responsible for past climate change and explain bigger extinctions like of the dinosaurs, now more commonly blamed on a giant meteorite strike.
Nature flagged its article "The day the Earth let rip" -- methane is an odorless component of burping or flatulence.