Link to jump to start of content The Seattle Times Company Jobs Autos Homes Rentals NWsource Classifieds
The Seattle Times The Climate Challenge


Friday, June 13, 2008 - Page updated at 11:53 AM


Ancient global warming traced to volcanoes

Los Angeles Times

Scientists believe they have solved the mystery of what caused the most rapid global warming in known geologic history, a cataclysmic temperature spike 55 million years ago driven by concentrations of greenhouse gases hundreds of times greater than today.

The culprit, the researchers reported Thursday in the journal Science, was a series of volcanic eruptions that set off a chain reaction releasing massive quantities of carbon into the atmosphere.

The eruptions occurred on the rift between two continental plates as Greenland and Europe separated.

In 10,000 years — a blip in Earth's history — the polar seas turned into tropical baths, deep-sea-dwelling microorganisms went extinct and mammals migrated poleward as their habitats warmed. It took about 200,000 years for the atmospheric carbon to be transferred to the deep ocean, allowing the planet to cool.

The event, known as the Paleocene-Eocene Thermal Maximum, was discovered in the early 1990s. Since then, scientists have studied it to better understand how Earth will respond to the current buildup of greenhouse gases.

The ancient warming was sparked by the release of 1,500 to 4,000 gigatons of carbon over several thousand years, scientists estimate. By comparison, emissions from human activities are about 7 gigatons a year — a much faster rate.

During the thermal maximum, "carbon was released over thousands of years," said James Zachos, a professor of earth sciences at the University of California, Santa Cruz, who was not involved in the study. "We're going to do it in a few centuries."

The cause of the ancient warming has been debated.

In the latest study, researchers from the U.S. and Denmark analyzed volcanic ash found on basalt cliffs in Greenland and buried under the floor of the North Atlantic. The samples showed the timing of the eruptions corresponded with the ancient warming.

Scientists knew that volcanic eruptions alone would not provide enough greenhouse gases to account for the warming — a jump of more than 9 degrees Fahrenheit.

The new study suggests the eruptions triggered a chain reaction involving land sediments rich in organic materials.

Lava flows "cooked" organic material as the continents divided, releasing greenhouse gases, said coauthor Robert Duncan, a professor at Oregon State University.

He described the organic material as a "turbocharger" that accelerated the warming.

Copyright © 2007 The Seattle Times Company

Seattle Times Special
Reports and Investigations

Miracle Machines: The 21st-Century Snake Oil
The Times has found that thousands of these devices, many of them illegal or dangerous, are used in venues nationwide.

The Favor Factory
The Times examined relationships between those who benefit from earmarks and those who make campaign donations to lawmakers.

Confronting Malaria
A look at the Gates Foundation's billion-dollar initiative to eradicate malaria.

Pike Place Market
Seattle's Pike Place Market turns 100 this year.

Your Courts, Their Secrets
Sealed records hold secrets of potential dangers in our medicine cabinets; of molesters; of missteps by local agencies.

License to Harm
The state allows hundreds of doctors, counselors, and others to keep practicing despite their sexual misconduct.

The Bering Sea
The Bering Sea is seeing dramatic changes due to global warming.

Olympic Sculpture Park
An interactive guide to Seattle's new park.