Ticking Time Bomb (methane-induced runaway greenhouse effect,

[Vitruvius]

possible human extinction)

by John Atcheson

The Arctic Council's recent report on the effects of global warming in the far north paints a grim picture: global floods, extinction of polar bears and other marine mammals, collapsed fisheries. But it ignored <SNIP> enormous quantities of naturally occurring greenhouse gasses trapped in ice-like structures in the cold northern muds and at the bottom of the seas. These ices, called clathrates, contain 3,000 times as much methane as is in the atmosphere. Methane is more than 20 times as strong a greenhouse gas as carbon dioxide.

Now here's the scary part. A temperature increase of merely a few degrees would cause these gases to volatilize and "burp" into the atmosphere, which would further raise temperatures, which would release yet more methane, heating the Earth and seas further, and so on. There's 400 gigatons of methane locked in the frozen arctic tundra - enough to start this chain reaction - and the kind of warming the Arctic Council predicts is sufficient to melt the clathrates and release these greenhouse gases into the atmosphere.

Once triggered, this cycle could result in runaway global warming the likes of which even the most pessimistic doomsayers aren't talking about. <SNIP> The most recent of these catastrophes occurred about 55 million years ago in what geologists call the Paleocene-Eocene Thermal Maximum (PETM), when methane burps caused rapid warming and massive die-offs, disrupting the climate for more than 100,000 years.

The granddaddy of these catastrophes occurred 251 million years ago, at the end of the Permian period, when a series of methane burps came close to wiping out all life on Earth. More than 94 percent of the marine species present in the fossil record disappeared suddenly as oxygen levels plummeted and life teetered on the verge of extinction. Over the ensuing 500,000 years, a few species struggled to gain a foothold in the hostile environment. It took 20 million to 30 million years for even rudimentary coral reefs to re-establish themselves and for forests to regrow. In some areas, it took more than 100 million years for ecosystems to reach their former healthy diversity.

Geologist Michael J. Benton lays out the scientific evidence for this epochal tragedy in a recent book, When Life Nearly Died: The Greatest Mass Extinction of All Time. <SNIP> The cause of all this havoc? In both cases, a temperature increase of about 10.8 degrees Fahrenheit, about the upper range for the average global increase today's models predict can be expected from burning fossil fuels by 2100. <SNIP> If we trigger this runaway release of methane, there's no turning back. No do-overs. Once it starts, it's likely to play out all the way.

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How likely is it that humans will cause methane burps by burning fossil fuels? No one knows. But it is somewhere between possible and likely at this point, and it becomes more likely with each passing year that we fail to act. <SNIP> We can't afford to have the first sign of a failed energy policy be the mass extinction of life on Earth. We have to act now.

John Atcheson, a geologist, has held a variety of policy positions in several federal government agencies.

More at http://www.commondreams.org/views04/1215-24.htm

See also related DU thread: Human extinction within 100 years warns scientist at http://www.democraticunderground.com/discuss/duboard.php?az=show_topic&forum=103&topic_id=92158