In law, we have a saying:
If the facts are on your side, argue the facts.
If the law is on your side, argue the law.
If neither is on your side, pound the table.
Tobin's personal attacks are pounding the table. It's a concession that I've won the point we were arguing. All he's doing now is trying to distract attention away from the fact that his claim that water vapor is 4% of the atmosphere is absurd. He's had pages and pages now to come up with a single bit of evidence or even a single source to back him up. I've presented evidence to show that the 4% is too high. I've linked to a source to show that, even in the tropics, the average range of water vapor at the earths surface is 2-4%. Tobin is taking the high end of that range and claiming it applies to the entire atmosphere. I've linked to data showing that water vapor content falls off rapidly as you go above the earth. I've also linked to evidence that the mass of water vapor in the atmosphere is around .3 (with generous rounding upward). That means there is about 5X as much water vapor as CO2 in the atmosphere, instead of the 100X Tobin claims. (And the 1000X he originally claimed.) Tobin ignores all of it, and tries to justify his original claim with other irrelevant claims (also wrong, but we'll get to that) for which he provides no evidence or source. He's also admitted throughout this thread that factors other than relative quantity have to be examined in figuring out how a greenhouse gas works.
I'm perfectly satisfied that I've done what I set out to do in this section of the argument: show that Tobin's claim that CO2 can be dismissed as a cause of global warming based solely on the ratio of water vapor to CO2 in the atmosphere. It's a handy place to link to if he ever drags it out again in the future.
So now we move on to looking at the other factors. First up, absorption spectra. Upthread, Tobin made this argument:
Tobin wrote:Also, even though CH4 is 20 times more powerful of a greenhouse gas than CO2, there is a slight problem religious zealots like Brad fail to mention. It's a narrow band absorber which overlaps with another greenhouse gas H2O. And since there is vastly more H2O in the atmosphere that already absorbs the same spectrum as CH4, there really isn't any contribution made by CH4 to global warming.
Now, Tobin made that argument with regard to methane. The same argument gets made from time to time in various internet forums about CO2. The best way to understand the argument and understand why it's wrong is to read through the history of how this issue has been addressed since the 1800's. I think the best write up on that comes from Spencer Weart's A History of Global Warming. It is available online in a free, hypertext version. Here is the portion that discusses the history of CO2 in atmospheric sciences.
https://www.aip.org/history/climate/co2.htmIt's long, but I think it's well worth reading. There is also a TL/DR version here:
http://www.realclimate.org/index.php/ar ... -argument/In short, it's not true that the absorption spectrum of water vapor completely overlaps that of CO2. There is a water vapor window that permits CO2 to do it's greenhouse thing. And as you go upward from the surface of the earth, the overlap becomes smaller and smaller.
“The ideal subject of totalitarian rule is not the convinced Nazi or the dedicated communist, but people for whom the distinction between fact and fiction, true and false, no longer exists.”
― Hannah Arendt, The Origins of Totalitarianism, 1951