Talk:Runaway greenhouse effect

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What is Runaway greenhouse effect

I've decided I know what a RAGE is, and so I'm going to edit the page to reflect that. I think this will be useful, because it then becomes clear that its different from RACC, and why, which might even help define that, too William M. Connolley (talk) 22:27, 16 February 2009 (UTC)

Another hasty and poorly-researched edit, William. I've easily found a couple of sources which clearly use the term to descrive AGW, and changed the article accordingly. I've left the main bulk of the article about the Venus-type situation, though.Andrewjlockley (talk) 10:03, 17 February 2009 (UTC)

Nope, you've found a couple of confused people, so I've reverted that out. Stick to RaCC for now William M. Connolley (talk) 19:34, 17 February 2009 (UTC)

First only uses runaway in the headline. Within the body, they are more cautious and say "rapid global greenhouse warming". The second is the grauniad and is hopelessly confused. Those are Hadley GCM results - there is no RGE there, just some fedbacks. As usual, you don't even read your sources any further than their headlines, because you just don't care William M. Connolley (talk) 19:38, 17 February 2009 (UTC)

The definition in the first sentence is the one that I am familiar with and, probably more importantly, supported by the literature. -Atmoz (talk) 18:39, 18 February 2009 (UTC)

The definition wasn't supported by a peer-reviewed source, and was removed. Indeed it directly contradicted a source already in the article. WMC seems not to have read the citations, as a source which SPECIFICALLY discussed RAGE is used to support it's non-existence! I suggest we revert WMCs arbitrary demerge of this article, as the peer-reviewed articles use RAGE to describe the terrestrial events dealt with in RACC. I'll merge-tag it now.Andrewjlockley (talk) 01:06, 19 February 2009 (UTC)

Don't blindly revert like that without looking for sources. There are many referred sources that define runaway greenhouse effect in this way. For example this one. -Atmoz (talk) 02:53, 19 February 2009 (UTC)

Hope you can drop a couple in the copy, AtmozAndrewjlockley (talk) 23:40, 20 February 2009 (UTC)

William, I strongly disagree with what appears to be your original research. A look at the most cited papers about "runaway greenhouse effect" shows that the only common definition possible is "a major temperature increase due to a positive feedback loop". google search

Touisiau (talk) 12:48, 25 February 2009 (UTC)

Refs to papers are good. Do you mean this one? I'm amenable to change, if you can clearly demonstrate what you mean William M. Connolley (talk) 14:34, 25 February 2009 (UTC)

Here are some very cited refs which don't match your too narrow definition:

"Thermostats, Radiator Fins, and the Local Runaway Greenhouse" <1784%3ATRFATL>2.0.CO%3B2&ct=1&SESSID=dbef884db06ab234b3ed1243570782d9

"How to kill (almost) all life: the end-Permian extinction event" [1]

Touisiau (talk) 22:25, 25 February 2009 (UTC)

Neither of you links worked for me. [2] looks to be your second, and I agree, it says RG, but its written by a bunch of ecologists, not climatologists (well, [3] is the first author) and these are not the people to define RaGE for you William M. Connolley (talk) 23:06, 25 February 2009 (UTC)

[4] is probably your second. They don't source their defn William M. Connolley (talk) 23:11, 25 February 2009 (UTC)

We can distinguish between the way the terms used by different people, if necessary.Andrewjlockley (talk) 00:16, 26 February 2009 (UTC)

H&S

Someone gave me this, so I shall share it:

Annual Review of Energy and the Environment
Vol. 25: 441-475 (Volume publication date November 2000)
(doi:10.1146/annurev.energy.25.1.441)

WATER VAPOR FEEDBACK AND GLOBAL WARMING1

Isaac M. Held and Brian J. Soden


The size of nondimensional ratio, ?H2O, provides a measure of the
strength of the water vapor feedback. If ?H2O ? 0.4, water vapor
feedback increases the sensitivity of temperatures to CO2 by a factor
of ? 1.7, assuming that I and C are fixed.

If the value of ?H2O were larger than unity, the result would be a
runaway greenhouse. The outgoing infrared flux would decrease with
increasing temperatures. It is, of course, self-evident that the Earth
is not in a runaway configuration. But it is sobering to realize that
it is only after detailed computations with a realistic model of
radiative transfer that we obtain the estimate ?H2O ? 0.4 (for fixed
relative humidity). There is no simple physical argument of which we
are aware from which one could have concluded beforehand that ?H2O was
less than unity. The value of ?H2O does, in fact, increase as the
climate warms if the relative humidity is fixed. On this basis, one
might expect runaway conditions to develop eventually if the climate
warms sufficiently. Although it is difficult to be quantitative,
primarily because of uncertainties in cloud prediction, it is clear
that this point is only achieved for temperatures that are far warmer
than any relevant for the global warming debate (22).

—Preceding unsigned comment added by William M. Connolley (talk • contribs)

DOI problem

Please provide more info on doi|10.1175/1520-0469(1975)032. I was not able to determine the correct article for this. Q Science (talk) 06:03, 20 February 2009 (UTC)

It takes me to this article, which deals with Venus. But, skimming it, I cannot find any reference to a runaway greenhouse effect. Also, its 34 years old. That does not make it bad science, but it makes it a tad outdated, especially since we had the Vegas and Cassini there fairly recently, and currently have Venus Express in orbit. --Stephan Schulz (talk) 08:56, 20 February 2009 (UTC)

I found the same article using a google search, but not when using http://dx.doi.org/. The full DOI for that article is

10.1175/1520-0469(1975)032<1133:IOTVOP>2.0.CO;2

As a result, I want the person that entered the DOI to confirm that that is the correct article or to correct the DOI. Q Science (talk) 17:57, 20 February 2009 (UTC)

Why not find a source you think is better? I am not keen on it, but it does seem to be the 'grandaddy' source.Andrewjlockley (talk) 23:34, 20 February 2009 (UTC)

Sorry - could you first identify the article in question? Is it the one I dug out? If yes, can you be specific (page, column) about where Kawabata and Hansen mention a runaway greenhouse effect? --Stephan Schulz (talk) 23:46, 20 February 2009 (UTC)

Fixed. Apologies, this page isn't on my watch. That's fixed too. I wasn't being rude, Stephen, I just didn't realise my mistake and I didn't 'hear' you. Sorry.Andrewjlockley (talk) 03:03, 25 February 2009 (UTC)

B&T

What does Events which would meet Benton and Twitchet's definition of a runway greenhouse... mean? What is B&T's defn? Why is it here? William M. Connolley (talk) 20:48, 7 March 2009 (UTC)

cite added. They used the runaway term to describe the PT and PETM, which made it a relevant cite. Website's down, so you've got a bare URL atm. Sry!Andrewjlockley (talk) 02:36, 8 March 2009 (UTC)

Benton and Twitchett claim that volcanoes raised the temperature of the Earth so high that methane hydrates melted and increased the amount of Greenhouse Gases, which increased the amount of warming so that additional hydrates were released. They then define this scenario as a 'runaway greenhouse' phenomenon. Q Science (talk) 21:39, 13 April 2009 (UTC)

Earth

The article contains the following statement:

Climate scientist John Houghton has written that "[there] is no possibility of [Venus's] runaway greenhouse conditions occurring on the Earth".

However, a runaway greenhouse effect may occur in the distance future due to the rising luminosity of the Sun. See paragraph 5, Future of the Earth#Climate impact for example. Thanks.—RJH (talk) 14:28, 8 May 2010 (UTC)

Without having checked in detail, my guess would be that there is an implicit "within the current geologic epoch" in JH's quote William M. Connolley (talk) 18:32, 8 May 2010 (UTC)

This section is a bit patchy. The relevance of the first sentence isn't explained, and the second sentence "In the current climate the gain of the positive feedback effect from increased atmospheric water vapor, as well as Earth being too far away from the Sun at its current luminosity for such to occur is well below that which is required to boil away the oceans" is broken. Someone should fix it; I can't even be sure what it is meant to say. Waylah (talk) 13:03, 29 November 2018 (UTC)

Broken

This article is quite badly broken, due to the definition it uses. So, we start with:

A runaway greenhouse effect occurs when, on a planet with substantial reserves of greenhouse gases in liquid or solid form, some forcing occurs to begin to gasify them, leading via positive feedback to complete gasification of these reserves.[1][2] The planet Venus is believed to have experienced a runaway greenhouse effect, which led to its oceans boiling away.

The problem is the mixing of two different meaning of runaway. "gasification of reserves" is one possible defn, but (a) it doesn't actually imply any particularly large temperature change and (b) it isn't the defn ref 1 provides. Ref 1 [5] defines it as "It would become a runaway greenhouse effect if the rising temperature approached the boiling point of water, because then the oceans would begin to convert to water vapor, the water vapor would increase the effectiveness of heat trapping and accelerate the greenhouse effect, this would cause the temperature to rise further, thus causing the oceans to evaporate faster, etc., etc. (This type of runaway is also called a "positive feedback loop".) When the oceans were gone the atmosphere would finally stabilize at a much higher temperature and at much higher density, because all the water would now be in the atmosphere. " So, Venus had a runaway but Earth (obviously) didn't.

Ref 2 [6] is, I think, useless and should be removed William M. Connolley (talk) 16:14, 24 July 2010 (UTC)

Agree, Ref 2 is useless. In addition, since the phrase "runaway greenhouse effect" does not appear in the IPCC WG1 (2007 text or Glossary, except in the title of one reference), this article should say so. Q Science (talk) 20:33, 24 July 2010 (UTC)

I think this whole thing needs a major re-vamp. We probably have AJL to thank for much of this William M. Connolley (talk) 20:41, 24 July 2010 (UTC)

The top 3 from wikichecker

• Andrewjlockley (18)
• William M. Connolley (12)
• Atmoz (5)

The poor source was added today by Twang (not AJL). Q Science (talk) 21:05, 24 July 2010 (UTC)

OK, I didn't check that, what I meant was the whole tone of the thing. E.g. stuff like [7]. Clearly AJL ground me down in the end William M. Connolley (talk) 21:23, 24 July 2010 (UTC)

I've done the intro into something that I now think is sane. Probably the article text needs reworking too William M. Connolley (talk) 20:54, 24 July 2010 (UTC)

Biased towards a "there is no cause for alarm" viewpoint?

I've just reverted [8]. Looking, I think the previous section applies.

I don't think:

Some may feel that runaway greenhouse effect is not a clearly defined term, but it alludes to the potential for what has happened to Venus to happen to the Earth

is accecptable: its either a well defined term, or it isn't. If it is, find the sources that say so, and evidence that it is used. Nor is:

The term is not generally used by the IPCC, which has generally been shown to be conservative (i.e. unduly optimistic)

If you want to say that the IPCC is unduly optimistic, you need very good sources.

However, the only sense in which "runaway" (in the sense of a runaway train whose brakes have failed) is poorly defined is...

looks like personal opinion to me William M. Connolley (talk) 10:17, 2 April 2012 (UTC)

With all due respect, what either you or I think is completely irrelevant; what is important is what has happened and what is happening: Is surface temperature and pressure on Venus 90 times that on Earth (or not)? Was this caused by positive feedback mechanisms inducing irreversible increases in GHGs (or not)? Is there evidence of positive feedback mechanisms kicking-in on Earth (or not)? In all three cases the evidence demands an unequivocal "Yes" and, therefore, your objections are all entirely spurious: Runaway greenhouse effect is not a poorly-defined term; you just seem determined to obfuscate it.

As for the IPCC being prone to undue optimism, there are many sources to support this assertion, not least the wording of the UN Resolution by which the IPCC came into being - which grants the right of line-by-line and word-by-word review of every IPCC report and - effectively enabling simple majority voting at government level to obfuscate any scientific consensus. See Biello (2007), 'Conservative Climate Consensus document may understate the climate change problem', Scientific American, April 2007.

As I said to you on your Wikipedia user profile page, you - like many others - appear to be in denial of reality.Mlack65 (talk) —Preceding undated comment added 12:55, 2 April 2012 (UTC).

Sorry, but "runaway greenhouse effect" is incompletely defined. Not every positive feedback is strong enough to overcome the t⁴ negative feedback from the Stefan–Boltzmann law - i.e. even a series of positive feedbacks can converge at some relatively low level of temperature effects. Moreover, many of the feedbacks are self-limiting. Once the arctic permafrost has thawed completely, there will be no additional GHG emissions from that source. Do you call it a "runaway greenhouse" even if it stops before boiling off the oceans? Or is that a requirement? Yes, many competent scientist think the IPCC is a bit on the conservative side. But very few indeed think they are ridiculously conservative. --Stephan Schulz (talk) 14:43, 2 April 2012 (UTC)

Guys-- the "runaway greenhouse" is a very well-defined concept in the planetary science community, and refers to a state (or a transition to a state) in which liquid water cannot be sustained at the surface (although in a more general sense it can apply to other greenhouse species that condense and feedback onto temperature, for example on exoplanets that operate in a different temperature-pressure regime), though the astrobiologists think that liquid water is a pre-requisite for life so that is the most studied case (and most applicable to Earth). In the water vapor runaway case, it requires the surface temperature to approach the critical point of water (~647 K) and, depending on the size of the surface reservoir, temperature can greatly exceed this value. The temperature does not cease to increase until the entire reservoir no longer exists at the surface. The "runaway greenhouse" does not refer to the release of CO2/methane from permafrost, or other carbon cycle feedbacks, and in fact these things would not trigger a runaway...although I understand some have used this terminology colloquially, but it would be better to define them as some sort of tipping point or abrupt climate change than a "runaway." The physics of the runaway is well-documented, though I suspect not well-known to people not directly working on issues related to planetary crises, habitability, etc. It requires a sufficient amount of stellar influx of energy (or other heat sources, such as tidal heating) to cross a certain threshold value, which depends somewhat on the gravity of a planet and the degree of subsaturation that is maintained in the atmosphere...most estimates for Earth have this at ~300 W/m2, about 60 W/m2 higher than the current influx of solar energy, so Earth will eventually runaway as the sun brightens over geologic time (there's also an intermediate "moist greenhouse" case where hydrogen is lost rapidly but liquid water can still exist). It is virtually independent of the CO2 concentration since in the runaway limit, the atmospheric opacity is almost completely set by the water vapor concentration. One the incoming flux of energy exceeds this so-called Nakajima-Simpson limit, the planet can never reach radiative equilibrium since that is the maximum amt. of energy a planet can emit with a water vapor feedback. The physics of that limit are also documented, and there's another so-called Komabayshi-Ingersoll limit that is an upper bound on how much a wet stratosphere can emit (though this isn't really reached in practice since the other one occurs at a lower value) 169.226.41.99 (talk) 18:15, 3 April 2012 (UTC) -- Chris Colose

It would be good idea to put a few refs here to the literature that well-defines this concept,in that case William M. Connolley (talk) 20:32, 3 April 2012 (UTC)

I don't know if I should modify the article myself (I propose not, because it would change completely), but some good starting references: are 1) Nakajima, Shinichi, Yoshi-Yuki Hayashi, Yutaka Abe, 1992: A Study on the “Runaway Greenhouse Effect” with a One-Dimensional Radiative–Convective Equilibrium Model. J. Atmos. Sci., 49, 2256–2266 , 2) F. Selsis, J. F. Kasting, B. Levrard, J. Paillet, I. Ribas, and X. Delfosse, 2007: Habitable planets around the star Gliese 581?. A&A 476, 1373-1387 , 3) There's an arXiv preprint with a pretty decent review: The Runaway Greenhouse: implications for future climate change, geoengineering and planetary atmospheres Colin Goldblatt, Andrew J. Watson, 2012, Accepted in Phil. Trans. Roy. Soc. Lond. A on 28 Dec 2011 , 4) Ray Pierrehumbert's textbook goes into some of the details too , 5) The Kasting (1988) reference already in the article is a pioneering paper as well 169.226.41.99 (talk) 20:54, 3 April 2012 (UTC) - Chris Colose

Redefined

After this [9] edit to the lede, some of the subsequent text needs updating; for example:

Potential runaway greenhouse effects on Earth may involve the carbon cycle, but unlike Venus will not involve boiling of the oceans.

cannot be true any more William M. Connolley (talk) 07:09, 4 April 2012 (UTC)

I've made some changes to the article, including new sections and links. Cmc0605 (talk) 21:48, 4 April 2012 (UTC)Chris Colose

C to F

The temperatures provided in the article are in Celsius, but everyday U.S. citizens will have no idea what the temperature is in Fahrenheit. In many articles, there are alternate measurements given in parentheses and this should be done here. Because some people like myself, just find the article, confusing to read, because we do not know what the temperature actually is. And it should not be up to individuals to have to go to another website to compute measurements, as wikipedia articles are meant to be disseminated in layman's terms. Stopde (talk) 11:56, 3 April 2013 (UTC)

Good idea, Template:Convert is a useful way of providing such conversions. . dave souza, talk 19:04, 3 April 2013 (UTC)

Careful though! There are different formulas for absolute temperatures and temperature differences. Template:Convert supports both, but is fairly often misapplied. --Stephan Schulz (talk) 22:43, 3 April 2013 (UTC)

Instead of preaching, I just did it. Let me know if I overlooked something. --Stephan Schulz (talk) 22:50, 3 April 2013 (UTC)

Good job I appreciate it. Stopde (talk) 20:23, 4 April 2013 (UTC)

"Greenhouse Effect" is the same as a "Runaway Greenhouse Effect"?

A Greenhouse Effect means heat is trapped more than usual, but it also means that more heat from the sun is added, and that causes a build-up of heat that just keeps building up hotter and hotter, until some factor changes (eg. less pollution, more photo-syntheses, or some other factor.) That is the REAL definition of a "greenhouse effect'. It is the same as a 'Runaway Greenhouse Effect", so the fact that it builds up hotter and hotter forever, unless some other factor changes. The current 'greenhouse gas' effect on Earth, if it is letting heat escape faster than it can build up, is not a greenhouse effect. It is just warmer. The real definition of a greenhouse effect is that the temperatures have 'runaway', and unless something changes that, then it will not stop building up hotter. Its just to clarify terms. Its the same thing. — Preceding unsigned comment added by 24.63.50.134 (talk) 14:14, 19 August 2013 (UTC)

Thanks, I think the distinction is that the greenhouse effect causes warming which can level out, the runaway effect would keep going, or at least keep going until conditions were completely changed. . dave souza, talk 09:03, 1 April 2014 (UTC)

No, the RGE is a peculiar type of GE and is due to the Kombayashi–Ingersoll limit. The reason involve a deep understanding of greenhouse physic and is it is probably beyond the scope of wikipedia. — Preceding unsigned comment added by Albert0 (talk • contribs) 13:33, 7 November 2014 (UTC)

it is probably beyond the scope of wikipedia - oh, OK, we'll ignore it then William M. Connolley (talk) 14:01, 7 November 2014 (UTC)

Greenhouse effect on Venus not substantiated by valid physics

NOR

It cannot be substantiated with standard physics that the surface of Venus is kept hot by radiation from the colder carbon dioxide atmosphere. The small solid core of Uranus (55% the mass of Earth) has a surface temperature several times that of the Venus surface, and yet only about as much methane as Earth has water vapor. Uranus is nearly 30 times further from the Sun than Earth is, and thus receives little more than 0.1% of incident solar radiation. In fact the surface temperature of Venus rises by about 5 degrees (from 732K to 737K) during the four-month-long day and so this requires an input of thermal energy, which cannot be coming by way of radiation from the colder atmosphere because, if it were, entropy would be decreasing. Venus cools by 5 degrees at night, and so it could easily have cooled right down over the life of the planet if the Sun provided no insolation. So we can deduce that it is energy from the Sun which is gradually raising the temperature of the Venus surface during those four months of Earth time. But less than 20 watts per square meter of solar radiation gets through to the surface because carbon dioxide actually absorbs incident solar radiation. If one tries to explain the 5 degree difference with Stefan-Boltzmann calculations for radiation, there is a difference of about 450 watts per square meter just between the two temperatures 732K and 737K, and so this is not supplied from the direct solar radiation which is only about one tenth of that which reaches Earth's surface. Hence there is no scientific basis for assuming that direct radiation to the surface is the cause of the high surface temperatures on Venus, and thus there is no "runaway greenhouse effect." Consequently this whole article should be removed. Douglas Cotton (talk) 02:14, 1 April 2014 (UTC) Is the date of your comment significant? Certainly a fringe view, and appears to be original research. . dave souza, talk 09:04, 1 April 2014 (UTC) It's a whole bunch of hooey. The Uranus thing is trivially explicable by the fact that the pressure at Uranus' purported (models can fit the data without a solid core) surface is many orders of magnitude higher than on the surface of Earth or Venus (millions of bar vs. 90 bar for venus). The 1 bar temperature on Uranus is a mere 80K. Also Uranus' interior may have trapped heat from formation. Douglas Cotton is a known climate troll who has been banned by many climate websites including Lucia's and Dr. Spencer's. I expect wikipedia will follow suit if the behaviour pattern carries over to here. Sailsbystars (talk) 18:31, 1 April 2014 (UTC) http://stoat-spam.blogspot.co.uk/ William M. Connolley (talk) 20:55, 1 April 2014 (UTC)

Questions about Venus, and misleading terminology

WP:FORUM w/o ideas for article improvement

It seems to me that this article has a number of problems, and should be withdrawn prior to being rewritten with careful oversight by a panel of appropriately qualified scientists. The article as it stands seems to me to be misleading and to have the potential to damage the reputation of Wikipedia. I am not a scientist, but am university-trained and have read and studied a good deal on science and engineering. I do a lot of engineering-type calculations. Rather than state facts, I think it best that I ask questions here, and merely refer to obvious or universally agreed facts. Reference 1 does not seem to accessible any more. Is the present atmosphere of Venus really due to any runaway process whatever? Did Venus ever have oceans or any liquid water at all (bearing in mind its proximity to the sun), though it probably had water vapour? Is it certain that there was still a good deal of water in the Venusian atmosphere by the time the planet had fully formed, or had most of it been "blown away" already? What would it mean to say that the oceans (if there were any) had "boiled away"? If the water in a pot on the stove "boils away", it remains in the atmosphere. Is it not the case that, even if there had been liquid water and that it became too hot for it to remain liquid, that it would remain in the atmosphere until being "blown away"? Is it not true that, even if there had been no carbon dioxide on Venus, the water would have blown away in any case? In this is case, would not any greenhouse principle on Venus be irrelevant or of minor significance? I seem to remember hearing Professor Brian Cox state on television that the reason that Venus has a dense CO2 atmosphere is that there was not enough water on Venus to form carbonic acid and to form carbonate rocks, which is largely what happened to the earth's CO2. The article states: "Carbon dioxide, the dominant greenhouse gas in the current Venusian atmosphere, owes its larger concentration to the weakness of carbon recycling as compared to Earth (which requires liquid water), where the carbon dioxide emitted from volcanoes is efficiently subducted into the Earth by plate tectonics on geologic time scales." Is it the RECYCLING of CO2 which is the issue rather than carbonate rocks being formed at all, whether or not with recycling? The article notes that "Other large-scale climate changes are sometimes loosely called a 'runaway greenhouse' although it is not an appropriate description", and "On much longer timescales, such processes can potentially spell the end of life on Earth due to the gradual increase in brightness of the Sun as it expands into a red giant in about five billion years". Yet the article continues to refer to the "runaway greenhouse effect". Would it not be better to identify the wrong use of this term, and not to use it in the article? As it is, we read, stated as though it were a matter of fact: "Most scientists believe that a runaway greenhouse effect is actually inevitable in the long term as the Sun gradually gets bigger and hotter as it ages." It is plain that things can get hot without any greenhouse principle being involved. Does this statement not contain a misleading usage of the type already referred to in the article? Is it not the case that if a runaway greenhouse effect were possible on the earth in the near future then it would have taken place in the past when CO2 levels were anything from 3 to 10 or more times higher than they are now? Graphs of ancient CO2 levels are here... http://www.physforum.com/index.php?showtopic=11103, and here... http://earthguide.ucsd.edu/virtualmuseum/climatechange2/07_1.shtml. It seems to me that the article should draw attention to this reason for believing that a runaway greenhouse scenario on the earth is highly unlikely. The article doesn't give a clear account of what the greenhouse effect is. It provides a link to http://en.wikipedia.org/wiki/Greenhouse_effect, which begins badly by not explaining immediately that the effect is due to greater absorption of long-wavelength radiation than of radiation having shorter wavelengths. (Instead it waffles on about scattering - I will make this the subject of question about that article separately.) A link to a good article would be fine, but the article itself should contain a brief explanation of the essentials. 58.179.112.84 (talk) 06:05, 4 December 2014 (UTC)

58.179.112.84 (talk) 13:25, 4 December 2014 (UTC)

Main sequence

Removed sentence referring to last stages of the life cycle of the solar system as this is unrelated to a runaway greenhouse effect except in that they both would make the earth uninhabitable. Even mention of this is out place so deleted instead of redacting. Lycurgus (talk) 13:26, 27 June 2015 (UTC)

Hothouse Earth is NOT the same as runaway greenhouse effect...

In contrary, as Steffen et al. demonstrate, a hothouse Earth state is a stable state: It is certainly nothing we would like to experience, as the temperatures and also sea levels would be substantially increased, but it would not mean that all water keeps evaporating. This is different for the runaway greenhouse effect: Here, the temperature rises and rises and rises, as more and more water evaporates until the entire oceans are evaporated. This is what is assumed to have happened on Venus. As Steffen et al. show, our climate system might easily reach the hothouse Earth state, maybe even if we strictly follow the Paris Agreement (i.e., 2K), but as other authors have demonstrated, it is not very likely that our climate system will end up in a runaway situation. Again, both situations would be terrible for mankind, and we are currently on the hothouse Earth path, but it is important to distinguish them from each other. I would strongly suggest to disentangle these two different scenarios and create an own article for hothouse Earth, maybe based on Steffen et al.'s important paper. We have done so in the German Wikipedia some time ago (maybe have a look at Google translations of de:Treibhaus Erde and de:Galoppierender Treibhauseffekt for inspiration). Flugscham (talk) 15:55, 4 February 2019 (UTC)

A few years ago, I thought just as you do, and went looking for sources to make the argument. But instead I found sources that used "Runaway greenhouse effect" for both (A) unstoppable feedbacks leading to a new but stable climate state and (B) venus effect. I don't have them in front of me, but as so often in new fields of research as efforts are made to coin and define phrases they are often given multiple, maybe overlapping, meanings. Ah well. It is not our job to fight the fight to imprint these terms with the "correct" definition. Better to clearly explain the idea of climate feedback and the two possible outcomes, a stable hotter-house if not indeed a hothouse earth, versus Venus effect. If readers understand the concepts, we can claim victory even if the terminology is muddled more than we like. That said, maybe since I looked into this a few years ago a strong international consensus has formed around these definitions. If so, that's new and changes things. I suppose too that since I'm writing off my memory, I might be remembering wrong. Thoughts? NewsAndEventsGuy (talk) 14:17, 10 February 2019 (UTC)

I've changed the redirect to greenhouse and icehouse Earth. I've come across quite a few sources that equate greenhouse and hothouse earth, while I've not come across sources linking hothouse earth to the runaway greenhouse effect. Femke Nijsse (talk) 10:58, 23 February 2020 (UTC)

Proposed Restructuring

Hi all, I am assigned to edit this page through a graduate level class on Planetary Atmospheres. Looking at this page, I think the following structure would be a useful organization for the page:

• History
• Physics of the Runaway Greenhouse
  • Feedbacks
  • Limits on Outgoing Longwave Radiation (OLR)
  • The Moist-Greenhouse Effect
• Habitability
• In the Solar System
  • Venus
  • Earth
    • Relation to Climate Change
    • Future

I also plan on adding more detail under the physics section, discussing the runaway greenhouse effect as fundamentally a limit on the OLR and flux received from the Sun/star. I plan on cleaning up the feedback section and incorporating it into the discussion of the physics of the runaway greenhouse. I'd also like to better flesh out the section on Earth and especially both distinguish between the runaway greenhouse effect and tipping points in the climate, as well as add more sources to the discussion on whether anthropogenic climate change can result in a runaway greenhouse or moist-greenhouse. Seeing as this page has quite an extensive talk page, I wanted to make sure I let people know my intentions and possibly get their feedback before I started drafting and eventually editing.--SincereScience (talk) 01:40, 2 June 2019 (UTC)