The Island of Doubt

The new warning comes from one Sergei Zimov, chief scientist at the Russian Academy of Science's North Eastern Scientific station, which Reuters describes as "three plane rides and eight times zones away from Moscow." Here's the essence of his scary scenario:

For millenniums [sic], layers of animal waste and other organic matter left behind by the creatures that used to roam the Arctic tundra have been sealed inside the frozen permafrost. Now climate change is thawing the permafrost and lifting this prehistoric ooze from suspended animation.

But Mr. Zimov, a scientist who for almost 30 years has studied climate change in Russia's Arctic, believes that as this organic matter becomes exposed to the air it will accelerate global warming faster than even some of the most pessimistic forecasts.

"This will lead to a type of global warming which will be impossible to stop," he said.

When the organic matter left behind by mammoths and other wildlife is exposed to the air by the thawing permafrost, his theory runs, microbes that have been dormant for thousands of years spring back into action. As a by-product, they emit carbon dioxide and - more damaging in terms of its impact on the climate - methane gas.

According to Mr. Zimov, the microbes are going to start emitting these gases in enormous quantities.... "The deposits of organic matter in these soils are so gigantic that they dwarf global oil reserves," he said.

It's another of those infamous positive feedback loops, in which a warming Arctic melts the permafrost, turning a methane sink into a methane (and CO2) source, which warms the atmosphere further, which melts more permafrost. If enough methane and CO2 are released, the cycle could be disastrous. In theory.

The question is, how much methane is available and how much warming will it take to tip that cycle into a runaway feedback loop? ZImov says the world's permafrost areas hold 500 billion tonnes (Gt) of carbon. Others give different numbers. Back in 2005, the University of Alaska at Fairbanks, where most American research on the subject is centered, estimates, 32,000 Gt -- of methane and CO2, which is "one million times as much as the CH4 released in the atmosphere of all northern ecosystems." That sounds like a lot, and it is. Natalia Shakhova, a visiting researcher at the UAF, predicted that "a very small disturbance of gas hydrates could cause catastrophic consequences within a few decades."

But the possibility of large-scale release of methane from the arctic tundra, and from peat bogs elsewhere on the planet, remains a controversial subject. David Archer at Real Climate looked at the state of the science in October of last year. His conclusion:

According to one set of papers, atmospheric methane could be suppressed in the future by controlling land fires. Or it could be that methane variations are mostly produced by wetland emission, driven by climate change as well as land use decisions, according to another set of papers. Or methane could resume its rise, toward a new steady state, because it is driven by increasing fluxes from melting permafrost peat and hydrates, according to observations on the ground.

The bottom line I take away from all this is that the available studies come to a strikingly divergent range of conclusions. We know a lot about the methane cycle, but as far as forecasting the near-term future, we have no clue.

And here's the first sentence of the abstract of a paper published just last week in Nature on this very subject:

Large uncertainties in the budget of atmospheric methane, an important greenhouse gas, limit the accuracy of climate change projections

But in that paper, Katey Walter of the UAK's Institute for Arctic Biology and her colleagues report that "methane flux from thaw lakes in our study region may be five times higher than previously estimated."

..the approximate 500 Gt of labile Pleistocene-aged C in ice-rich yedoma permafrost could greatly intensify the positive feedback to high-latitude warming by releasing tens of thousands of teragrams of CH4 [tens of Gt] through ebullition [bubbling] from thermokarst lakes if northeast Siberia continues to warm in the future, as projected.

So there are hints that things might be bad. But Walter's study is only of the Siberian Arctic. Still lots of unknowns. As the AP's Seth Borenstein wrote in his coverage of Walter's study:

Some scientists say this vicious cycle is already underway, but others disagree.

Plus ça change