Dire Degrees

MAN-MADE greenhouse gases are being released into the atmosphere 30 times faster than at the time when the earth experienced a previous episode of global warming. A study comparing the rate at which carbon dioxide and methane are being emitted now compared to 55 million years ago when global warming also occurred has found dramatic differences in the speed of release.

James Zachos, professor of earth sciences at the University of California, Santa Cruz, says the speed of the current build-up of greenhouse gases is far greater than during the global warming that took place following the demise of the dinosaurs. “The emissions that caused this past episode of global warming probably lasted 10,000 years. By burning fossil fuels, we’re likely to emit the same amount over the next three centuries,” he told the American Association for the Advancement of Science in St Louis.
He warns that studies of global warming events in the geological past indicate that earth’s climate passes a threshold beyond which climate change accelerates with the help of positive feed-backs — vicious circles of warming. Professor Zachos is a leading authority on the episode of global warming known as the Palaeocene-Eocene Thermal Maximum, when average global temperatures increased by up to five degrees Celsius due to a massive release of carbon dioxide and methane. His research into the deep sediments of the ocean suggests that at this time about 4.5 billion tons of carbon entered the atmosphere over a period of 10,000 years. This will be the same amount of carbon released into the atmosphere from cars and industrial emissions over the next 300 years if present trends continue, he says.