More open thread for everyone!
>>Neither Stu nor I object to [all the forcing GHGs to be taken into account]
>Uh, you’ll need to read Stu’s comments again:
>>>Because you haven’t explained why CO2 providing 1/4 of the total greenhouse forcing doesn’t mean it hasn’t got a 4x feedback factor.
Stu, in response:
>>__Other non-consensible greenhouse gases contribute to the greenhouse effect__. This means that the total greenhouse effect does not scale on a 1 to 4 basis with carbon dioxide. How could it, when if you scale it down to zero there is still some greenhouse effect left?
Which is correct. If CO2 contributed 1/4 and the other forcing GHGs contributed 1/20, that would give 3.3X.
[It appears](http://scienceblogs.com/deltoid/2010/08/open_thread_53.php#comment-2875132) that instead, CO2 contributes 1/5 and the others contribute 1/20, which does give 4X.
Yes I’m happy with all Dave has said, although I will note a minor quibble in that he’s only getting exactly the same 4x answer as Wow because of how the figures have fallen; Wow’s 25% from CO2 is exactly the same as Dave’s 25% from all non-consensible GHGs. Though now I’m pretty sure Wow is saying that the other 5% are pretty much feedbacks anyway via the carbon cycle.
If the ‘denial’ comment was directed at me I cannot see why; I have even presented an alternative calculation and got an answer of 3.2x feedback factor. Not so different, no denial, just a different method that, I thought, included more variables, was less simplistic, and therefore possibly closer to a true feedback value pre-albedo changes.
However that calculation did mix source material; Wow’s original 25% from CO2 (I forget the exact source) and Schmidt et al’s 20% left after CO2 is taken out.
I haven’t been exercising denial of any kind, nor have I done nothing but simply point a finger at Wow and said ‘you’re wrong’. If I have been unclear at any point, maybe that’s because my judgement was clouded when Wow pissed me right off.
> Stu, in response:
> > Other non-consensible greenhouse gases contribute to the greenhouse effect. This means that the total greenhouse effect does not scale on a 1 to 4 ba
me in response:
> Methane turns into carbon dioxide. Methane produced by decay of plants and animals that grew from sequestering hydrocarbons. Hydrocarbons produced from CO2 in the atmosphere.
Why I’m so pissed off is because people here aren’t reading what I’m saying, but what they think I’m saying.
Therefore you can’t just wave your hand and say “this is because of other gasses”.
And, Stu, again, it’s 66% H2O, 34% Other, making 3:1 sensitivity.
So, if you include non-CO2, you don’t get 4:1.
Which is irrelevant anyway because that’s not what I’m asking you to do.
E.g. if you had turned around and said “Well, I think it’s even more likely if you take all non-CO2 forcings you get 3:1 and that is a better starting point than 4:1″ I wouldn’t have anywhere near the problem with you I have.
But no, you go “It’s wrong.”.
It’s easy to tear down something as long as you aren’t fussed about building anything in its place.
Ask any denialist.
>E.g. if you had turned around and said “Well, I think it’s even more likely if you take all non-CO2 forcings you get 3:1 and that is a better starting point than 4:1″ I wouldn’t have anywhere near the problem with you I have.
Well that’s pretty much what I’ve been trying to say, so sorry I couldn’t articulate it to your liking. But my posts do not just amount to ‘It’s wrong’; throughout I have been trying to explain what I thought was wrong and why. FWIW I think you got hot under the collar too quickly, shouted me down and just repeated the same point (that is, the point that had caused me concern in the first place). It was like trying to whack a square peg into a round hole with a frying pan.
But I’m not Stu PID. Don’t be so damn childish.
I acknowledged your point about methane/carbon cycle in a post above. That much of the other non-condensible GHG longwave flux is feedback to CO2 is probably a reasonable assumption. I note, having had the time to read all of Schmidt et al., that their model does not use a carbon cycle. I also note that in the model they in fact do not let the model equilibriate after removing the CO2 – indeed, they only take the longwave flux over one year and find that it goes down by 14%; no doubt over time the reduction in water vapour etc would bring the total longwave forcing very significantly, but to what I don’t know! And yet that elusive figure is still what I’m looking for.
The only hint is when they say
>Indeed, a model simulation performed with zero GHGs gives a global mean temperature changes of about −35°C and produces an ice covered planet
but, d’oh, that includes albedo feedback too, which we don’t want. And it dunnae tell you whether they forced the model to have no WV, or let that happen by taking out all the non-condensible GHGs.
>And it dunnae tell you whether they forced the model to have no WV, or let that happen by taking out all the non-condensible GHGs.
They took out all the non-condensing GHGs and let it run for 50 simulation years. It’s described in the other paper, which doesn’t seem to be available online, but there’s more information about it [here](http://www.giss.nasa.gov/research/briefs/lacis_01/).
>After 50 years, the global temperature stands at -21 °C, a decrease by 34.8 °C. Atmospheric water vapor is at ~10% of the control climate value (22.6 to 2.2 mm). Global cloud cover increases from its 58% control value to more than 75%; the global sea ice fraction goes from 4.6% to 46.7%, causing the planetary albedo of Earth to increase from ~29% to 41.8%.
Grand – good stuff Dave.
Interesting for sure for understanding the greenhouse effect, but I realise how convoluted the thing I’m looking for is; no CO2 (or any non-condensible gases), but also no change in albedo. Such a thing of course is unphysical, but then so is calling the Earth a blackbody, which is just a tool/stepping stone to understanding radiation balance.
Notify me of followup comments via E-Mail.
The thread, there is more.