Thursday, March 17, 2011

IPCC Model Off by a Factor of Two

No shit

In a paper in Environmental Science and Technology Libia R. Diaz-Valbuena, Harold L. Leverenz, Christopher D. Cappa, George Tchobanoglous, William R. Horwath, and Jeannie L. Darby crawl down into the cesspool and measure greenhouse gases generated in septic systems. Turns out to be about a factor of two less than the models used by the IPCC, which, as any sane person can tell you were not checked against a rather odious reality, but rather estimated from biological oxygen demand. This study is obviously a front runner for the 2011 IgNobels.

More, although not much, seriously there are a large number of septic systems out there, and while GHG emissions are small compared with those from fossil fuel combustion, in the US, about 0.12 tonnes equivalent to CO2 per person per year, compared to 23 for the total carbon emissions per person in industrialized countries, they are not quite zilch. This illustrates another major failing of the IPCC dependence on models.

Cue the wailers.

10 comments:

bigcitylib said...

Which of the authors did the actual dirty work? I assume there's a grad student or two on that list.

Anonymous said...

Does the IPCC have an estimate for cow-fart-emitted CH4 in need of "hands-on verification" by enterprising teams of wailers?

John Puma

Steve Bloom said...

The bunny encouraging the wailers? Don't reggae that beat, mon.

EliRabett said...

Where are the auditors when you need them?

Rattus Norvegicus said...

I expect that Watts will pick up the scent of this one any momemt...

badger badger badger said...

I think he should have volunteers go out and check each monitoring site, and post photos.

Somebody be sure to tell Inhofe.

Steve Bloom said...

Pick up the scent? Hah! He'll be swimming in it.

Jakerman said...

So this will require an slight upward adjustment to climate sensitivity? Given that the current warming is forced by less GHG than thought.

Steve Bloom said...

I'm not sure what it might mean for the models, Jakerman, but the key point is that it's a very small factor. Carbon sources and sinks are notoriously hard to measure, and there are much larger ones that remain inadequately characterized. The important ones are those that are large (or will become so) and will undergo significant change with further warming (which the septic tank source won't). If you google, you'll find that papers adjusting the size of sources and sinks (present and/or future) are quite frequent. An important one relating to permafrost came out just a few weeks ago.

Steve Bloom said...

Just to add, remember that the current source and sinks all must add up to what's measured in the atmosphere, so there would be no net adjustment to the models.