Not consciously as I never thought about it but certainly that must be true as it is without exception, I think , that whenever one "unbinds" a collection of bound atoms, some form of energy must be supplied - could be given by a passing cosmic ray's electric field impulse, and it is a stretch to call that endothermal, but it is. (Of course if the freed atoms re-combine in some more tightly bound system, then the net could be exothermic.) I was aware that a branch of the Gulf stream's denser water flowing along the Siberian coast line's bottom (as seems to be starting) deliveres the required thermal energy much more effectively than ice-free Arctic waves mixing surface water down (with help of gravity) does. I.e. the waves drive water toward the shore and it rises higher than an equal gravitational potential surface. - Just like in creation of El Nino, water rises up even 20 feet higher along Asian shores.
BTW thanks for your list of links on methane burps, etc. I'll work my way thru them, I hope, when have time. I know of several too, but mostly from people in the Arctic Emergency Group (or others with that POV). I assume your list is less biased. Right now I am studding Brillvon's second link. It is aware of both your 1988 link and Hanson 2009 paper - one saying thermal run-a-way can't happen and the other that it is certain, if business as usual continues.
This paper's model has Earth's atmosphere with oceans adding H2O and various loads of CO2, and leans to conclusion that thermal run-a-way is not possible until the sun get hotter, but admits that may be false in the last sentence of the conclusion. Earlier in the paper it admits that the conclusion may b false and lists some reasons - one being lowering of albedo down to 0.16 from current 0.32 via ice and snow melting, (or high clouds with more black particles in them, I'll add). Another is the model considered only CO2 & H2O, but another GHG, considered as well, which would block the escape of IR in couple of identified wave length band where water vapor is not a good absorber and also admits that even water has an absorption continuum when two molecules collide, (as they would in dense steam atmosphere) may let thermal run a way happen. That continuum absorption increases with the square of the density - but was ignored even though the density became huge as most of the oceans became vapor.
I admit I am a little confused by their discussion of this as they also say they are using a grey radiator model for the IR. - Perhaps they mean that instead of the complex, computationally expensive, use of actual line structure in the stronger IR bands, they just assigned a less than unity but constant emissivity with the net IR as "reduced black body" - that dependency on temperature and ignored the continuum outside of the stronger absorption bands?
I was well of the fact IR does not escape from the surface but from higher up (roughly from one "optical depth" deep in the atmosphere) but did not fully appreciate that this leads to a max IR escape limit and run-a-way is only possible if the rate of absorption is greater (or if the assumption made of a grey IR radiator is false - as it is in the wave lengths band he names for water.) One of the first things I will do is look at CH4's absorption bands.
Also very interesting and new to me was that when one considers the atmospheric circulation, Hadley cells - see drawing at end, the equatorial region can be in "incomplete thermal-run-a way" with energy convected towards the poles, where it escapes to make a stable system, with that transport effectively raising the max IR loss rate possible. - I. e. Earth has several hotter stable states - not just current one and "Venus like" one. Probably even coolest of these hotter stable states make mammals extinct. I encourage you to read this recent paper which is much more in doubt on the question of thermal run-a-way. - It calls for more complete modeling effort before any conclusion is to believed as fact.
PS I had trouble getting Brillvon's second link to open but via Google & title, found it here: http://arxiv.org/pdf/1201.1593v1.pdf It is from January 2012, by real experts very aware of prior work on the question. - I find it very hard to believe that any doubt free answer to the thermal run-a-way question exists.* - It is not that just iceaura has not looked at the literature enough - Currently thermal run-a-away is an open question, as these authors admit - too many not fully valid assumptions used and many things, including methane, and water vapor continuum absorption blocking IR's escape in those wave length regions, just ignored, in the analysis done.
Interesting too is fact confidence in the "not possible" answer is so low that one section discusses: What will be the warnings? and another: What could we do, if warning are available - best answer they think is to move earth farther from the sun via interaction with an asteroid - much like man picks up "gravitational assist" by near misses of other planets (some times even 3 or 4) to get his spacecraft to the outer planets.
Another interesting thing I learned, quoting: "the entire ocean will not boil: a liquid ocean remains until the critical point is reached at Tc = 647K." This is because as much of the ocean does evaporate the atmospheric pressure is greatly increased and boiling point at high pressure is too - finally there is no boiling point as the vapor and liquid are one and the same.
* Again, this question is only of "academic interest" becuase man will never confirm the answer even if it is possible, as man will have been extinct long, very long, before it can be observed (unless man has colonized Mars, etc. except if transition occurs quickly (huge CH4 burp OR by the much more likely process I note is possible** after the Hadley cell diagram below.
** I bet that there are other rapid processes, not I or anyone, have thought of. After all the transition is an inherently unstable positive feed back driven process. I am reminded of man's POV 50 years ago about how easy it should be to hold a fusion plasma in a magnetic bottle. - Well it wasn't - We still can't but we now know about 30 different instabilities mother nature knew of all along that lets the plasma do what it wants too instead of what man hopes for. I don't think this is exactly what Guy MaPherson had in mind, but it might have been, when he named his blog about near term extinction (by 2030): "Nature Bats Last."
Last edited by a moderator:
