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Mixed message on methane
October 28, 2009 - 8:28pm

A word to the wise (and otherwise): don't get H1N1. Just don't. Do whatever you need to do, but minimize your likelihood of infection. It comes on fast, it comes on strong, and you're not worth a tinker's dam while you're down with it. Not fun.

So now, on a lighter note, let's talk about swamp gas. Landfill exhalations. Cow farts. Methane.

If I have a major quibble with the approach in the WBGU report I was commenting on last week (and will have a couple more comments on in future), it's that it lumps methane in with carbon dioxide for greenhouse gas accounting purposes and so, by implication, for mitigation planning.

Now, I understand some of the reasons for handling methane that way. Burn fossil fuel and you don't just get CO2, you also get methane and nitrous oxide. The quantities are small, compared to the CO2 you get, but the multipliers are significant (like 21 and 310 -- that's how much more powerful GHGs methane and nitrous are than CO2). So for fossil fuel combustion, it's easy to account for the three gases at the same time, and the mitigation steps you're likely to take (like burning less of that stuff, or switching from coal to natural gas) affect all three simultaneously.

But there are also reasons why methane should be tracked separately from CO2. For starts, there are activities (like decomposition of organic matter in the absence of oxygen, or operation of a confined animal feeding operation) that produce lots of methane but little or no CO2. To mitigate these emissions, you need to be thinking along very different lines. And, to my mind more important, methane behaves very differently, as GHGs go, from carbon dioxide.

Carbon dioxide takes years (some say decades) to rise to the level in the atmosphere where it has its greatest GHG effect. On the other hand, once it gets there, it stays for millenia. Methane, conversely, becomes effective as a GHG very quickly but also tends to break down within about a decade or so. (In fact, the multiplier for methane used to be even higher, before scientists determined just how short-lived its effect is.)

One of the implications of that difference in behaviors is that, if we want to make a significant near-term impact on the effects of accumulating greenhouse gases, one thing that might make sense is to attack our methane emissions fast and hard. We can't solve the climate change problem by eliminating methane output alone, but you've got to start somewhere. And reducing methane emissions could create a short-term negative blip that's not caused by a downturn in the economy. (Think of the psychological impact of the recent report that US GHG emissions have decreased as a result of the current economic situation. Could any single news item do more to solidify the link in people's minds between addressing climate change and going into economic free-fall?)

Anyways, I'm not absolutely convinced that the WBGU should have proposed addressing methane separately from CO2, but I'm also not sure they got it right. Simple has its advantages, and they're already proposing a number of other approaches which increase complexity. Since there are fewer reasons to account for nitrous oxide emissions separately from CO2, maybe we might just as well leave methane as part of the CO2-equivalent accounting community.

It's all so hard to think about. Especially when your whole body still hurts.


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