Carbon Dioxide
Seeing as it seems to have caused a bit of a stir here...

Carbon Dioxide is not the 'strongest' greenhouse gas. In fact, one of the most potent is water vapour. The difference, of course, is that we have a direct effect on the levels of Carbon Dioxide in the atmosphere, but our emission of water vapour is negligible.

However, by increasing the amount of CO₂ in the atmosphere, we have probably served to nudge the global average temperature up by a small amount.

What then happens is that the slightly increased temperature leads to increased rates of evaporation from the seas, lakes, etc. With more water vapour in the atmosphere, we get another slight increase in temperature, and thus a little bit more water is evaporated.

Unfortunately - because, as I said, our own direct production of water vapour is minimal - we can't directly control these water vapour levels. The reason governments have to bang on about CO₂ concentrations is because that's one of the few things we can directly influence.

So there is an argument for saying that the CO₂ we've belched out has indirectly exacerbated global warming. Reducing CO₂ emissions may seem like a vain hope to some, but it's one of the few options we've got if we want to try and limit what damage might occur due to rising temperatures. Whether you want to try and reduce your emissions, or whether you just don't give a fuck, I leave entirely up to you. (Just noticed richardm's point about China as well, which does make it seem kind of futile. Oh, well. /clings to energy-saving light bulb and hemp shopping bag)

(The increased CO₂ concentration is quite hard for us to deny - it's shot up from about 280ppm to 380ppm in a geologically negligible timescale; whatever you want to say about the natural vs anthropogenic effects, we have to accept the blame for that raised concentration.)
(LongJohnBaldry, Thu 19 Feb 2009, 17:59, 3 replies)

Everyone talks about carbon dioxide
because everyone knows what it is.

For me, this is evidence that the layman's science is simply not strong enough, and thus I have stopped listening to anyone who isn't a meteorologist or geologist.
( Digeridude Lord Wellington's Beef Trapeze, Thu 19 Feb 2009, 18:20, closed)

I'm an atmospheric physicist
Working on the spectroscopy of atmospheric water vapour.

Do I count?
(LongJohnBaldry, Thu 19 Feb 2009, 18:26, closed)

only barely
and that's because you used subscript 2s on your CO2 :-P
( Vipros. clever got me this far, then tricky got me in, Thu 19 Feb 2009, 18:30, closed)

What's the code to do that?
_{is it this?}

ooo it is!
(The Oscillating Gibbon is eating curried squid, Sat 21 Feb 2009, 9:13, closed)

This is one of the things about planes
that makes their contribution to the whole climate change debate more significant that the 3% of CO₂ emissions that routinely gets trotted out.

When they fly along in the stratosphere, they leave a lot of water vapour up there which hangs around for a long time causing a problem.
(Bazongaloid, Thu 19 Feb 2009, 23:00, closed)

Well,
the difference is actually that the percentage of water vapour in the atmosphere is nearer to 5% whereas CO2 is nearer to 0.01%. Therefore the absorption bands of H2O are almost completely saturated whereas the fringe bands of the CO2 have yet to be.
(The Oscillating Gibbon is eating curried squid, Fri 20 Feb 2009, 0:00, closed)

Well, that and
correct me if I'm wrong, but I believe water vapour absorbs over a much larger portion of the infrared spectrum. (The large band between about 2 and 20 microns is thought to be more or less one big continuum, which is a lot wider than the adjacent CO₂ band around 15 microns.)
(LongJohnBaldry, Fri 20 Feb 2009, 10:23, closed)

Yeah I think that's correct,
it's been too long since I studied all that *gets a book out*
(The Oscillating Gibbon is eating curried squid, Sat 21 Feb 2009, 9:13, closed)