Talk:Global warming/temp

First paragraph

I've edited the temp version to incorporate the proposed first paragraph that I posted on the main article's talk page. As compared with the protected version, I edited the last two sentences so that the paragraph makes references to gases other than carbon dioxide but clarifies that, although they contribute to the greenhouse effect in general, they aren't the primary focus of current theories about the recent changes in the greenhouse effect (i.e., global warming). This text seems to be consistent with each of the divergent views expressed on main article's talk page. JamesMLane 07:04, 27 Feb 2005 (UTC)

Except that water vapor is very central to the current theories about changes in the greenhouse effect, it's just that the current page does not reflect this very accurately. CO2, at the concentrations present in the atmosphere, is too weak to make the results quoted here from climate models.

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) This is just POV stuff all over again. WV is a feedback not a forcing. The details of this can and should be discussed on the GHE page, not on the GW page.

I SAID WV is a feedback, and that feedback is essential to the theories predicting a significant warming. There is no POV whatsoever to that, it's simple fact, and for reasons which escape me you've systematically fought against the inclusion of this information, leaving a gaping hole in the description of how climate models predict a significant warming. Because this is essential to the predicted warming, it needs to be described on the page discussing that warming. — Cortonin | Talk 23:33, 28 Feb 2005 (UTC)

The climate models are making those predictions by including a strong positive feedback system involving water vapor. The theory goes that CO2 will make it slightly hotter, and being slightly hotter will cause more water to evaporate, causing there to be more water vapor, which makes it even hotter, causing there to be more water vapor, which makes it even hotter, until this balances out resulting in a strong positive feedback from a much smaller change in temperature due to CO2. This is why we have been opposing calling water vapor an "unimportant" or "insignificant" greenhouse gas for the increases, because without its consideration in the system, the results obtained are rather insignificant. — Cortonin | Talk 23:12, 27 Feb 2005 (UTC)

The text says that global warming is "caused primarily by anthropogenic (human-generated) carbon dioxide." That seems to me to be accurate. There's no suggestion that human activity is directly and significantly increasing the water vapor, or that some completely natural process is having that effect. Rather, water vapor is part of the mechanism by which the anthropogenic carbon dioxide increases global temperatures. Well, for that matter, so is the Sun. The whole greenhouse effect would be meaningless without sunlight. The point is that water vapor, while not "unimportant" or "insignificant" (the text doesn't say either of those things) is indeed "less important" because it's just a dependent variable, not the one that sets the process in motion. JamesMLane 02:36, 28 Feb 2005 (UTC)

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) WV shouldn't be called unimportant. In the intro, there is no cause to mention it at all.

- - -

Three points

1. Water vapor versus carbon driven is the distinguishing factor between natural and human causes.

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) Where did you get that from? Its not true.

If, as is generally believed, global warming is caused by AGHG, then yes Carbon Dioxide and other trace persistent gases (methane, NO2, aresols) drive the process. If the global warming is, as some maintain, driven by exogenous solar activity, then water vapor, not CO2 is the driving component.

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) No - if its driven by solar, then the driving force is... solar.

This is the crucial divide between primarily human generated and primarily nature generated. This because if solar irradience is the primary factor, then it will increase the amount of percipitable water, and this will act as a greenhouse gas. This effect will see warming primarily in the equitorial regions, most effected by sun, and with the highest water vapor pressure. This is one reason why the deglaciation at the poles is considered important, it is a strong indication that the poles are warming more quickly, or as quickly, as the equator, and therefore it is far less likely that water vapor is the driving gas, and therefore less likely that the process is natural solar irradience driven. The data on solar irradiation is very complex, but the most recent work indicates that solar irradiation is not strongly enough coupled to temperature to produce the effects that we have seen, and that the probable range of variation is not sufficient to produce the warming of the last 50 years. However, it may well be the case that solar radiation is augmenting the warming process. If this is the case, then the amount of warming atributable to AGHG is less than thought by some models.

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) I very much doubt that much of that makes sense. But if you can find a good source for it, I'll reconsider.

2. Water vapor is going to contribute more of global warming in human generated models While it is very likely that human generated carbon cycle gases that are driving warming - in most models more than half of the net human attributable global warming ends up being from water vapor. The reason skeptics focus on water vapor is because if models can knock out that positive feedback loop, or turn it into a negative feedback loop, then the problem of global warming is a great deal smaller than presently projected - manageable with current rates of decarbonization. Similarly, the worst case scenarios have a stronger feedback relationship. In essence, water vapor modelling is where the conflict is, because it is the largest single variable which has not been pinned down. So far when measured, the results have pointed to larger, not smaller effects, and towards positive, not negative, feedback.

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) This is true, but its fundamentally a detail. Put it in with the detail - on the GHE page perhaps.

3. While carbon cycle gasses are driving the process, it is water vapor that will be the single largetst determining factor in the climatic outcome, since water vapor moves a great deal of heat around. Not just human generated heat either - many models predict significant changes to weather patterns based on more storms leaving the tropics. Again, this is the most complex variable, and the one which, depending on how it behaves, makes the most difference in predicted outcome. Since the question, at this point, is overwhelmingly "how bad is it, and how much do we have to cut emissions?" it has assumed a central role in the debate over the best course for dealing with global warming, and the cost/benefit analysis that is associated with this.

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) Why say "carbon cycle gases"? Why not just "CO2"? And could you please source "many models predict significant changes to weather patterns based on more storms leaving the tropics". In most (all?) GCMs the WV change pattern is actually fairly simple - the RH stays about constant.

So the "dependent variable" idea is not accurate, instead, water vapor is where the greenhouse action is, and the question of AGW is how the heat generated by us plugging the carbon dioxide hole is going to effect it. Carbon is the fuse, but water vapor could well be the powder keg.

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) But this is not a helpful way of explaining it.

Thus while the skeptics are holding out that there is some negative feedback loop - like the "Iris effect", which hypothesizes massive convective cooling as one example, though the data isn't very promsing for it at this point - the alarmists are also looking at water vapor, because a relatively small change in feedback results in very large changes in final result. If you look at the consensus models, there are basically two groups at this point: bad and worse. Bad says that eventually negative feedback asserts itself, and effects level off. Worse says that it doesn't, or at least not in any time frame that is relevant to human planning.

Stirling Newberry 04:58, 28 Feb 2005 (UTC)

1. Actually, solar radiation seems to be seriously considered as significant by most climate change researchers studying solar effects. See my recent post on the main global warming talk page. As for deglaciation, it's been happening since long before industrial times. It doesn't seem prudent to take something which has been happening and suddenly claim credit for being the cause of it without strong causal evidence. — Cortonin | Talk 17:53, 28 Feb 2005 (UTC)

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) There may be some selection bias there. What you've said doesn't reflect the state of the science, as reported by IPCC.

But it does seem to reflect the state of the science, as found in journals. You should know by now that I'm not an IPCC worshipping fundamentalist. — Cortonin | Talk 23:33, 28 Feb 2005 (UTC)

(William M. Connolley 23:43, 28 Feb 2005 (UTC)) Oh come on, don't go all JG on us. You've picked 10 refs by some process unknown. That doesn't begin to compare with the careful analysis from the IPCC.

If by "process unknown" you mean a "literature search". What a funny concept to do a literature search on a scientific topic when we could just as easily take argument from authority. I searched through hundreds of articles on web of science listing solar and global warming, and picked out all the ones I found that made mention of solar forcing. And the result was that the overwhelming majority consider solar forcing significant or dominant. — Cortonin | Talk 00:27, 1 Mar 2005 (UTC)

2. Water vapor is a point of interest because it's critical to the predictions, poorly understood, and has a very complicated mechanism. Water vapor levels are intrinsically tied to cloud cover (which is thought to have a negative feedback overall, although this is complicated),

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) Source?

In the global average, cloud cover is responsible for a radiative forcing of about -27 W/m^2, with individual cloud types ranging from -100 to +20 W/m^2 (Hartmann 1993 chapter in Aerosol-Cloud-Climate Interactions). To zeroth order, more water vapor implies more clouds and hence a partial negative feedback, which is generally what is expected. Some people have argued that increased convection and storm activity might preferentially increase cirrus cloud cover, which would weaken the negative feedback or even make it positive. Jury is probably still out on that though. Dragons flight 23:13, Feb 28, 2005 (UTC)

(William M. Connolley 23:43, 28 Feb 2005 (UTC)) What you say is true but a bit hand-wavy. Some kind of source is desireable.

Given that the IPCC considers clouds "a dominant source of uncertainty" in GCMs [1] (http://www.grida.no/climate/ipcc_tar/wg1/271.htm), I doubt you are going to find any really firm answers beyond the qualitative more water vapor => probably more clouds => probably more negative forcing. Dragons flight 00:13, Mar 1, 2005 (UTC)

What do you need a source for? The negative feedback of clouds? You've stated it yourself before. The relationship between water vapor and cloud cover? I really hope you're not questioning that. — Cortonin | Talk 23:33, 28 Feb 2005 (UTC)

(William M. Connolley 23:43, 28 Feb 2005 (UTC)) Yes, for the -ve feedback of clouds. You've misunderstood what I said before: I said that the overall radiative contribution of clouds is -ve. Thats not the same thing (e.g. the overall contribution of the sun is +ve, but the sun isn't a +ve feedback).

and this is poorly understood. Water vapor changes the convective properties of the atmosphere (in a way that should result in more cooling), and atmospheric convection is extremely important to overall temperature, but this relationship also seems poorly understood. A factor of 2+ is pretty important if you're talking about a difference of 2 degrees or 5 degrees. — Cortonin | Talk 08:28, 28 Feb 2005 (UTC)

3. Due to the complexity, most predictions of storm increases are rather speculative. I haven't seen record of global storm increases yet which exceed natural variability. — Cortonin | Talk 08:28, 28 Feb 2005 (UTC)

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) Agree.

And as for the effects worsening, in the worst case, the worsening has to level off. Model predicted GHG induced warming is supposed to scale logarithmically with GHG levels. — Cortonin | Talk 08:28, 28 Feb 2005 (UTC)

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) But thats not what the models say: http://www.grida.no/climate/ipcc_tar/wg1/350.htm

I see nothing on that page which contradicts anything I said. — Cortonin | Talk 23:33, 28 Feb 2005 (UTC)

(William M. Connolley 23:43, 28 Feb 2005 (UTC)) You certainly implied a leveling off. That isn't seen.

Right, so it goes up indefinitely until the Earth dissolves into a ball of plasma. Never mind the laws of thermodynamics, they have nothing to do with global warming. *sighs and shakes head* — Cortonin | Talk 00:23, 1 Mar 2005 (UTC)

Oh, come on. You know there is no reason for the temperature rise to stop merely because the plasma stage has been reached. — SEWilco 07:35, 1 Mar 2005 (UTC)

 :) — Cortonin | Talk 08:15, 1 Mar 2005 (UTC)

Version to start from

(William M. Connolley 19:08, 28 Feb 2005 (UTC)) Both Silverback and I think we should start from the pre-SN version, and have edited here accordingly. The protected version was only in place because of the use - one wonders by who - of sockpuppet "User:WikiWarming".

GW unprotected

(William M. Connolley 23:45, 28 Feb 2005 (UTC)) Note that Ed has unprotected GW. This all might as well continue there. Splitting the discussion being just one bad result of 172's quite unnecessary protect.