Update: Methane Up in the Air

by Bill Chameides | December 2nd, 2008
posted by Erica Rowell (Editor)

Permalink | 7 comments

Though methane is a naturally occurring greenhouse gas, things like landfills, rice paddies, and deforestation increase methane emissions.

Here’s an update on the sudden uptick in the concentration of atmospheric methane, a potent greenhouse warmer.

Before we dig into the update, though, let me provide some background and context.

Methane is a potent greenhouse gas: pound for pound it is about 25 times more effective as a global warmer than carbon dioxide (CO2). Although it occurs naturally in the atmosphere, for example as a result of decay from organic material in swamps and other wetlands, human activities (such as growing rice, raising cows, cutting down forests, building up landfills, and mining coal) can also send methane into the atmosphere. (Here’s more on methane from wikipedia.)

Throughout much of the late nineteenth and twentieth centuries, methane concentrations increased quite substantially: more than a factor of 2, from about 0.8 to 1.8 part per million (ppm). But overall methane levels are considerably less than CO2 levels (~380 ppm). That is why even though methane rose more than CO2 and each methane molecule warms more than a CO2 molecule, the total warming from the methane increase is only about one fifth the warming from CO2.

Nevertheless, that’s a lot of warming. And given methane’s potency as a global warmer, it was a great relief to scientists when methane concentrations appeared to stabilize in the late 1990s.

But back in June, I reported on some preliminary data showing that methane concentrations had begun to inch up again in 2007. Well, that preliminary report has now been confirmed in a peer-reviewed article published in Geophysical Research Letters. Using data from a network of surface-sampling sites around the globe, Matthew Rigby and his colleagues at the Massachusetts Institute of Technology estimate that methane concentrations are now increasing with a current growth rate of about one half a percent per year. This rate of increase is smaller than the rate prior to the recent stabilization, but still significant.

What is behind the renewed uptick, and will the rise prove to be a short-lived perturbation or the start of a long-term trend? We don’t yet know. But stay tuned. We’ll keep you posted on what the research turns up.

filed under: carbon dioxide emissions, faculty, global warming, methane, science
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  1. charlie
    Dec 27, 2009

    Dr. Chameides Is there a way to encourage methane to separate out from air at the top of a building (like a barn)? thanks, charlie” title=”methane separation

    • erica
      Dec 29, 2009

      Charlie: Not without a lot of expensive chromatographic equipment.” title=”Dr. Chameides replies:

      • charlie
        Dec 29, 2009

        Thanks Erica, Is it feasable to build a chamber at the top of a barn into which lighter than air methane would settle; then to bleed off the mostly-methane to a central seperation system? This would act as a low-tech first stage “digestive system” which would ease the work of the “stomach” (that chromatographic stuff you spoke of). charlie” title=”methane capture

  2. Daniel Wedgewood
    Dec 3, 2008

    Dr. Chameides, I have to say that the idea of cows contributing to greenhouse warming provides some perverse satisfaction to me. I raised 3 cows a few years ago. They were Highland cows – they were self sufficient and interesting looking (that’s why I chose them). I had them fenced in a large field, where I gave them plenty of hay, organic grain, and water. You’d think they would have been thankful (at least until the slaughter – which never happened, by the way). Nope. To them, I was a short, two legged, less hairy, anti-cow devil. They still had their horns (to protect them from coy dogs and other miscreants), so when they gave chase (to me) it was a serious matter. They were surprising fast and had great peripheral vision. I didn’t take exact scientific measurements because of my high rate of speed at those times. One time a vet came, and they were all calm and compliant. He left, and I became target practice for their horns again. Ever try to quickly go through an electric fence? They really do work as advertised. I’m still not sure I can father kids. I actually think the cows laughed at me. An old farmer took them off my hands when I moved from Maine – think I should tell him they’re bad for the environment? – Dan ” title=”Belated Satisfaction

    • erica
      Dec 3, 2008

      From DR. CHAMEIDES – Dan – You should sign your comments as “ex-farmer Dan.”” title=”New signature?

  3. Daniel Wedgewood
    Dec 3, 2008

    Dr. Chameides, Are there any organisms, natural or bio engineered, that consume methane without producing greenhouse gases as byproduct? Dan” title=”Digesting Methane

    • erica
      Dec 3, 2008

      From DR. CHAMEIDES – Dan – Sure, there are lots of bacteria that consume methane – just do a Google search on “methane consuming bacteria.” But they can’t help much when it comes to greenhouse warming from atmospheric methane. The concentration of methane in the atmosphere (less than one part per million) is way too small for these kinds of bacteria to “make a living.” As a result, they are generally limited to special environments where methane concentrations are high – like hyrdothermal vents. To make these bacteria do the job, you would have to first separate the methane from the rest of the atmosphere and expose the bacteria to this concentrated methane. But if you’ve got methane concentrated, it makes a lot more sense to just burn it and generate electricity. After all, natural gas is basically methane.” title=”Yep but …

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