USA, December 18, 2011 (NY Times): Scientists struggle to understand one of the biggest looming factors about the future of the earth. Experts have long known that northern lands were a storehouse of frozen carbon, locked up in the form of leaves, roots and other organic matter trapped in icy soil — a mix that, when thawed, can produce methane and carbon dioxide, gases that trap heat and warm the planet. But they have been stunned in recent years to realize just how much organic debris is there. A recent estimate suggests that the perennially frozen ground known as permafrost contains twice as much carbon as the entire atmosphere.
And one day in 2007, on the plain in northern Alaska, a lightning strike set the tundra on fire.
Historically, tundra, a landscape of lichens, mosses and delicate plants, was too damp to burn. But the climate in the area is warming and drying, and fires in both the tundra and forest regions of Alaska are increasing. The Anaktuvuk River fire burned about 400 square miles of tundra, and work on lake sediments showed that no fire of that scale had occurred in the region in at least 5,000 years. Scientists have calculated that that single fire and its aftermath sent a huge pulse of carbon into the air — as much as would be emitted in two years by a city the size of Miami.
Edward A. G. Schuur, a University of Florida researcher, is worried that carbon buried since before the dawn of civilization is now escaping.
“To me, it’s a spine-tingling feeling, if it’s really old carbon that hasn’t been in the air for a long time, and now it’s entering the air,” Dr. Schuur said. “That’s the fingerprint of a major disruption, and we aren’t going to be able to turn it off someday.”
Martin J. Kennedy, a researcher at the University of Adelaide in Australia, said, “We are pushing the climate system harder than at any time in earth’s history. Are we not going to cross one of those thresholds soon?”