Runaway greenhouse effect?

One of the things that has always struck me as being problematic with CAGW is part of its reported origins. There have been individuals who suggested hydrocarbons could cause a problem with warming the planet very early in the 1900s and some in the late 1800s. Warming was not necessarily viewed as a bad outcome. Some people thought the warming could be beneficial.

So where did the catastrophic warming idea come from? NASA had a scientist, James Hansen, studying the planet Venus. He came up with a theory, borrowed in part from Carl Sagan, that Venus had fallen victim to a runaway greenhouse effect. This caused “the oceans to boil” (a fate Hansen has also publicly predicted for earth if we did not stop burning fossil fuels and increasing the CO2 in the atmosphere. Hansen modified his research on the runaway greenhouse effect and applied it to Earth. His research lead him to conclude the same thing could happen here.)

Unfortunately, there appears to be NO evidence that Venus ever had oceans, let alone looked like Earth. Everything we know about Venus we learned from looking through a telescope and from probes sent to penetrate the atmosphere and land on the surface. Venus is so inhospitable the probes burn up shortly after landing. The surface has been mapped from above. The composition of the atmosphere was determined. Beyond this, we have no clue as to whether or not Venus ever had an atmosphere that was Earth-like or if there were any type of lifeforms present. It’s all conjecture.

Mars was also looked as a possible way to learn more about our planet. Again, there is the belief that Mars may have been like Earth at one time. The surface of Mars does allow for exploration with a rover. Dust storms have been observed that lower the temperature rapidly, leading to speculation that similar forces are at work on Earth. Of course, Mars has very little atmosphere which makes such speculation questionable. It did seem to provide much excitement among climate scientists who claim this validates some of the climate change theory. Again, it is unclear how the behaviour of dust on Mars in any way explains the behaviour of dust on Earth. While physical laws are the same on all planets, that is where the similarity ends. Atmospheres are very different, as are surface temperatures, and so forth.

IF Venus was like Earth and fell victim to runaway greenhouse warming and Venus is governed by the same physical laws as Earth, Earth could fall victim to runaway greenhouse warming. Looking at Venus may help us avoid this fate if we study the forces contributing to this effect on Venus. Does this mean we could be subjected to the same fate as Venus? NO—there is no way to know unless there is definitive proof that Venus was once like Earth. Which there is not. Thus, the conclusion runaway greenhouse warming could occur on Earth does NOT follow. First, we must prove the phenomena actually occurred on Venus or Mars and then that we understand the mechanism by which this occurred. Lastly, we must prove the mechanisms that caused the runaway greenhouse warming on other planets can be modified to work for predicting such an outcome on Earth. Currently, we have no evidence to support any of these suppositions.

If we remove the concept of runaway greenhouse warming due to lack of evidence that such a thing has actually happened on other planets, there does still exist CO2 and it’s role in warming Earth. How much of the predictions concerning CAGW depend on Venus and Mars being role models? It’s difficult to say, but without an example of CAGW occurring anywhere in the past, predicting it will happen in the future is pretty much a toss of the dice.

Is the earth warming? Yes. Does that mean we are headed for a Venetian or Martian runaway greenhouse warming and destruction of Earth as we know it? It’s impossible to say. The evidence is just not there.


9 comments on “Runaway greenhouse effect?

  1. Tony Duncan says:

    Peter, once again you are stating well known facts along with assertions.
    yes, we all know that pressure relates to temperature. You seem to be saying that no matter WHAT the composition of Venuses atmosphere the temps would still be around 700° on the surface. you also are assuming that the pressure being that high is just the natural state of a planet like Venus. And that the CO2 content being so high is also perfectly normal. Could you reference the science that supports these contentions?

    • PeterB in Indianapolis says:

      Ideal Gas Law, PV = nRT

      Obviously, atmospheres do not behave “perfectly” as ideal gasses, but due to the ideal gas law, the temperature of Venus should be much much higher than that of Earth. One thing that is also discounted quite often when it comes to Venus, is that the clouds are known to be sulfuric acid. Even though there is precious little water vapor in the atmosphere of Venus, it is well known that the reaction of any water vapor with sulfuric acid is highly exothermic.

      I also believe that the extremely thick cloud cover is often discounted excessively. Thick clouds trap heat.

      I am not saying that CO2 contributes NOTHING to the temperature of the surface of Venus; however, I am saying that the contribution from CO2 is vastly over-estimated in my opinion. I will provide some links as soon as I am able.

  2. PeterB in Indianapolis says:

    It is well known that Venus is quite hot because it has “eternal clouds” and an EXTREMELY dense atmosphere, with an atmospheric pressure of about 92 “Earth atmpospheres”. Because the atmosphere of Venus is approximately 96% CO2, many mistakenly believe that it is so hot because of the “greenhouse effect” brought on by all of that CO2, but that is not really the case. The extremely high temperatures are much more a result of the intense atmospheric pressure than anything else.

    Just as with Jupiter, the temperature increases as the pressure increases, although the effects on Venus certainly aren’t as spectacular as the effects on Jupiter. However, regardless of the composition of the atmosphere of Venus, it SHOULD be far warmer than Earth, simply based upon the fact that the atmospheric pressure is 92 times higher than that of Earth.

  3. Tony Duncan says:

    I am not insulting you I am giving you my opinion. If you will stop making broad assertions about things and people without backing them up with accurate information, I will not express opinions that upset you. In your last post you were, in my opinion, insulting scientists without any basis for that insult. I honestly told you why I find that to be unreasonable. I did not call you any names and i explained why I respect scientists so much, even when I disagree with them.
    You have so far rarely responded to my specific points. You did in one post and I acknowledged that you had valid arguments.
    In the quote you mention. I said you were “ignorant” of what was going on. If you are not in fact ignorant of planetary studies and their value, you can easily accquant me with your knowledge and show me why these studies are actually a waste of time. I am confident that they are NOT a waste of time and that they do actually add important information to the issues around climate change. it is not an insult to question your knowledge. You just need to provide it.
    So I do NOT think you are an idiot and I comment on this blog in the hopes that you are really interested in sorting out the actual relevant facts on this issue. I have no problem with people disagreeing with me. i often learn as much from those people as those who agree with me, but i am not going to censor my real opinions and if you can’t tolerat that, it is your blog, and you can do what you want with it.

  4. “It is this kind o fthinking that I see so often form people who bash sicence. they take some study and make it sound ridiculus and a waste of tax payer money, and people who know nothing about science make a judgement that is totally ignroant of waht is actually going on.”
    Since you think I know nothing about science (and since you know nothing abut me–what degrees I have, what I work in, etc) I see no reason to continue to respond to your comments. Why would you bother to even comment on a blog you clearly think is written by a complete idiot? You have NO respect for people whatsoever. If they disagree with you, they know nothing about science.
    It’s pointless to even pretend you have any interest in anything other than insulting me. From here on out, you may post comments without insults and suppositions about people’s degrees and training, or you may go where and attack people you know nothing about So much for no ad hominem attacks. Just could not resist, could you?
    End of any further discussions. You are wasting my time. I have much better things to do.

  5. Tony Duncan says:


    Of course yu don’t owe anyone a complete explanation of historical figures, but you can at least put in context realvant facts that you do mention. Belief that increased temps would be beneficial was NOT based on any sort of science. In a short mention of Newton, would you make a point about how important he though Alchemy was?

    As for Hansen, as I expected he made no claims about what WOULD happen. He pointed out a worst case scenario. it does not sound very plausible to me, but it is not, as far as I know, scientifically impossible. he is correct that if we burn ALL fossil fuels in a short amount of time we will likely have close to the highest concentrations in the history of the planet, and the methane calthrate reservers are thought to be huge. As you know Methane is a MUCH more powerful GHG than CO2. If all the GHG are put in the atmosphere, then it might be possible to have a runaway greenhous effect. I would certainly say that this is alarmist and extremely unlikely, but I do not know that it is impossible. if it IS possible then it should at LEAST be considered. But in ANY discussion with the public it should be made clear that it is a very tenuous hypothetical and very unlikely possibility. I do not agree with Hansen’s approach to ACC. He previously made a claim that a 5 meter increase in sea level rise was possible fot his century. he was clear that this was not a scientific assessment but a conceivable possibility. Of course the Media and those opposed to ACC mischaracterized what he said. but he should know better, and for all I know he says these things on purpose knwoing they will be misrepresented. I strongly disapprove of that if he is doing that.
    you say we have no evidence of a runaway greenhouse effect on Venus. that is not my understanding at all. I just looked at Wikipedia on the issue and it makes perfect sesne to me. that doesn’t mean we know what actually happend on venus but saying we have no evidence of it seems completely unreasonable to me.

    As for Volcanoes bringign us out fo the ice Age, i think you are misapplying the connection. There is a strong possibility that a few times, the last as recent as 700 million years ago, the earth was almost completely ice covered. In that case it is thought that volcanoes emotted CO2 over millions of years and since there was no weatehring of CO2 on rocks or earth it accumulated in the atmospher and raised the global temps to reverse that.
    CO2 output CURRENTLY form Volvcanoes is farily well understood and there are weathering and ocean absorbtion effects, so that there is a rough balnace. Since CO2 levels have decreased over the last few hundred thousand years, it is likely that those weathering effects have decreased teh CO2 content and that corresponds to the decreasing temps since the holocene maximum 6-8 thousand years ago.
    Your making corelations between your mammal studies and climate science is just assertion and not using reasonable logic. It depends on what your studeis with mammals was. If it is what happens to mammals when i put them in boiling water, the correlation is quite high. if it is what happens when I put each on an ice floe off the canadian coast, then the correlation is low, yet you learn something about each animal. Your asumption that plaentary studies are “bad science seems arrogant to me. It is this kind o fthinking that I see so often form people who bash sicence. they take some study and make it sound ridiculus and a waste of tax payer money, and people who know nothing about science make a judgement that is totally ignroant of waht is actually going on.
    In almsot every single case when i look at what scientists actually do, i am astounded at the creativity, insight and rigourousness of the work being done. not ALL the time, but specifically in the case of cliamte science I see rather brilliant p[eople coming up with amazing ways to find information that is seemingly impossible to figure out. the history of the use of independant proxies in studying paleoclimate is incredible. Form plant stomata, to spores to pollen, ice cores to coral, there have been all sorts of ingenious ways that have been developed and refined and found to have dificulties and workarounds. I sutdied both astropphysics and evolutionary biology in college rather seriously and both fields have shown incredible progress in ways i never could ahve imagined. The same is happening for climate science in the last 30 years.

    Your question about “C” and “A:” in cliamte science boggles my mind. of COURSE you can have catastrophic consequences with out human interference. This has been more and more clearly established over 150 years of research . However over the last 12,000 years the climate has been relatively stable, globally since the last ice age. There is no indicationt that a new ice age was iminent in the next few thousand years anyway. The fact that the “A” is happening now and it COULD lead to the “C” should be of concern to everyone. Human population now is 7 billion. if you go back in time there are periods where it was thougtht to have been in the tens of thousands.Some of the reason for that is likely due to cliamte change over the period of the last couple of million years.
    Are you saying it doesn’t matter if there is some catastrope from climate change and a few bilion people are killed, as long as the human race survives it is all fine?.
    if not what exactly ARE you saying?

  6. Tony Duncan says:


    once again this sounds like a simplistic propoganda tool. your simplification of the history would easily lead one to a completely distorted view of the science. Of waht relevance is it that Arrhenius thought warming might be beneficial? he knew absolutely nothing of the potential consequences, and it is just of historical interest. Yet you leave it tantalizing as if his view on the subject is on any value today.
    Your explanation of Sagan and Hansen’s work on Venus, is so simplistic that you take the “oceans Boiling” as a literal quote, as if it has any relevance to the issue. If he had said “caused lead to melt”, it would mean the same thing, and I doubt you beleive there is no lead on Venus. You then state hensen said the same thing could happen to earth. I know of no one that contends earths global temps would exceed 100*C. Your stating that hansen beleives this could happen to earth requires a citation. I do not doubt that hansen has made statements that consider the most extreme possibilities, but i know of no scientific papers of scientists that contend that earths oceans are actually going to boil.
    It is decidedly not JUST conjecture about Venus’ atmosphere. We know from spectroscopic analysis that venus atmosphere is mostly CO2, and that it is not really possible for the atmosphere to have ALWAYS been mostly CO2. And we know the properties of CO2 well enough to know that the atmosphere must have developed over time and increased surface temps due to the pressure and the GH effect of CO2. We know that Earth’s temp would be significantly lower if not for CO2 and water Vapor, and we know that mars atmosphere does nto have enough total CO to raise the atmospheric temp sufficiently. there is nothing about the understanding of the inner planets that does not Support ACC.
    You just gloss over the properties of the planets as if there has not been serious thought about many many elements of planetary study that are vey well understood.
    there is no need whatsoever for Venus to ever have been anything like Earth to draw conclusions about the effect fo CO2, and making that statement again implies strongly that scientists who study these issues are just plain stupid and credulous. That is a postion I have seen many many deniers make over the last 4 years. I know of NO scientist, and a know afew personally, who are idiots and jump to conclusion based on such limited thinking about any subject

    you then make the ridiculous assertin that CAGW has not occurred in the past when every climate scientist and pretty much every skeptic and denier is quite familiar with past environments that were maybe 6°C higner than today. That cetainly falls under the category of CAGW,. and it has occurred for very long periods of time during earths past. In fact current temps are lower than average over the lifteime fo the planet. So we know that the arth can be much hotter than it is today, which makes the possibiliy of it occurring again, with geologically massive amounts pf CO2 and other GHG over miniscule (in geological terms) period of time to be a compelling and reasonable conjecture, that has been studied extensively over the last 30 years, with huge amounts of empirical evidence that support the possibility.

    As far as i understadn the evidence supports limits to any GHG forcing of temps beyond a certain amount. the rediative effect of CO2 is logrythmic, and only so much water vapor can be in the atmosphere unless soemthing causes temps to go extremely high. A runaway GH effect may be physically possible, but I know of no one that seriously thinks it si GOING to happen.

    • Arrhenius is an historical figure. I don’t owe anyone a complete historical analysis of a fact when I mention one. You can look that up on your own. This was theory at the time and that’s all. You can read in whatever nefarious connotations you like. It doesn’t change anything.

      James Hansen: Clearly, he is, in his own voice, talking about runaway greenhouse effects on Venus (which we have NO EVIDENCE of whatsoever) and then estimating how long earth would take to get there. He also says the volcanoes brought us out of the ice age, I think. I have not heard that before. Now all I hear is how volcanoes are minimal in their effect.

      Hansen did in fact modify his Venus theory and apply it to earth. I have found that documented in several places. He borrowed Carl Sagan’s theory and then adapted his “runaway venus greenhouse theory” to earth. In ‘Storms of My Grandchildren‘, Chapter Ten Hansen uses his climate crystal ball to foretell, “if we burn all reserves of oil, gas, and coal, there is a substantial chance we will initiate the runaway greenhouse. If we also burn the tar sands and tar shale, I believe the Venus syndrome is a dead certainty.”

      I am not glossing over planetary studies. I am questioning the use of two TOTALLY different planets as templates for what could happen on earth. This is done very frequently in climate science–NASA did it with the Mars rover and dust storms.

      If I decided to study monkeys in the Amazon to learn more about polar bears in the Arctic (both being mammals, both living on earth and both being ruled by the same physical laws), would that be “sound science”? I sincerely hope not and that no one would be foolish enough to call it that. Yet let climate science do the same basic thing and it’s “oh, these people are sooo smart and clever”. Bad science is bad science.

      How far back in climate change can we go and still keep the “A” in CAGW? If in the past “C” occurred while “A” existed, how are we having this conversation?

      “Possibility” is ANYTHING. Any idea you dream up for the future is possible. Probability combined with massive amounts of data, reproducible results (not just by a select few scientists) and a full explanation of how the results were obtained is science. Your comments on possibility have nothing to do with science.

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