A methane feedback from the past strikes again

What triggered the Palaeocene-Eocene thermal maximum (PETM) about 55 million years ago, which saw the fastest period of warming documented in Earth’s geological history? The PETM is associated with a rapid rise in greenhouse gases, particularly methane — but the big question is where did the methane come from?

bog.jpgThe most common answer has been the ocean (methane hydrates) but new research in Nature, (subs. req’d) casts doubt on the ocean theory, finding chemical evidence instead that the methane came from terrestrial sources, bogs, which were themselves stimulated by rising temperatures — an amplifying feedback. The lead author says:

“A lot of temperate and polar wetlands are going to be wetter, and of course warmer as well [because of current climate change]. That implies a switch to more anaerobic conditions which are more likely to release methane. That’s what’s predicted, and that would be a positive feedback – and we have evidence now that this is what happened.”

Indeed, research from last year found “thawing Siberian bogs are releasing more of the greenhouse gas methane than previously believed.” Why should we care about the source of the PETM?

Consider what scientists found when they analyzed data from a major expedition to retrieve deep marine sediments beneath the Arctic to understand the PETM, which they describe as a “widespread, extreme climatic warming that was associated with massive atmospheric greenhouse gas input.” This 2006 study, published in Nature (subs. req’d), found Artic temperatures almost beyond imagination–above 23°C (74°F)–temperatures more than 18°F warmer than current climate models had predicted when applied to this period. The three dozen authors conclude that existing climate models are missing crucial feedbacks that can significantly amplify polar warming.

That our climate models are underestimating global warming is a point I have many times. If bogs were a major amplifying feedback for the PETM, we may be in for “widespread, extreme climatic warming” if we don’t act quickly to slash greenhouse gas emissions before the same feedbacks kick in again this century.


2 Responses to A methane feedback from the past strikes again

  1. David B. Benson says:

    Yup. Somehow need to geet policy markers to move rapidly.

    Including ‘permanent’ carbon sequestration in the ground.

  2. Thanks, Joe, for keeping your blog current, interesting, educational … and poignant.

    And thanks for your invaluable cross-references … e.g., linking to this year-old post from today’s “The Garden of Eden had a 40-foot, 1-ton snake plus 90°F average temperatures” (2/8/09).

    In my TCP presentations, I emphasize that there was no ice when the CO2 concentration was ca 1000-2000 ppm while “fossil” fuels began their existence through photosynthesis 400- to 50-millions years ago: THERE WAS NO ICE until the CO2 concentration fell to 425 +/- 75 ppm, and as concentrations increase again from 385 ppm SOON THERE WILL BE NO ICE as Jim Hansen et al explain in “Target Atmospheric CO2: Where Should Humanity Aim?”

    90°F average temperatures will not destroy the planet (now ca 59°F), but will accelerate humanity’s demise … aka extinction.

    Would we could get the compelling underlying message out to ALL the Joe and Josephine the plumbers of the world, not just the choir who frequent this and similar blogs and slide show presentations.

    As George Carlin chides in (beware expletives) how do we get people to think immediately about “SAVING OURSELVES” instead of the more esoteric “SAVING THE PLANET”?