Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: Pumblechook on 03/03/2008 18:58:18

Title: Why is methane such a potent greenhoues gas?
Post by: Pumblechook on 03/03/2008 18:58:18

I asked elsewhere and nobody knows.

Title: Why is methane such a potent greenhoues gas?
Post by: Pumblechook on 03/03/2008 18:59:17

'Greenhouse' even.

Title: Why is methane such a potent greenhoues gas?
Post by: Bored chemist on 04/03/2008 19:04:04

"I asked elsewhere and nobody knows. "
Wrong on two counts. You didn't ask here, and I know.

Because it happens to absorb infrared radiation, in particular it absorbs wavelengths that most of the other constituents of air don't absorb. If it only absorbed the same wavelengths as, for example, water ten it wouldn't do as good a job as a greenhouse gas because most of that radiation is already absorbed- it would take a lot of methane to make a difference. Because it absorbs elsewhere in the spectrum it's really quite effective.
Of course there are other gases that do even better. The CFCs, in addition to killing ozone, are very potent greenhouse gases. Not only do their spectra generally differ from water, CO2 etc., but they are also very strong absorbers of radiation.