Comments 1 to 29:

1. Doug Hutcheson at 13:32 PM on 10 March, 2012
   This should be compulsory viewing in every high school. Watch the talk, then research the supporting evidence for every statement made. Making students do the search of the literature themselves might drive the facts home.
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2. Rob Honeycutt at 17:11 PM on 10 March, 2012
   Best talk I've seen Hansen give. And I totally dig the hat.
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3. Bernard J. at 20:14 PM on 10 March, 2012
   If science doesn't move the denialists, perhaps they should consider the escalating cost of action once even they can no longer deny the truth: 1) 3% CO₂ emissions reduction per annum had reduction started in 2005 2) 6% CO₂ emissions reduction per annum if reduction starts in 2013 3) 15% CO₂ emissions reduction per annum if reduction starts in 2022. As Hansen observes, the last is next to impossible - if voluntary control is desired...
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4. sauerj at 04:59 AM on 11 March, 2012
   Yes, very good talk! Maybe a bit too simple to sway hard-cores, but maybe simple is better! 3-Cheers to Mr. Hansen.
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5. Jose_X at 11:54 AM on 11 March, 2012
   Does anyone know how much success has come from research to sequester CO2? For example I had read of various lab success in using the sun, semiconductors, and/or bacteria to absorb CO2 and turn it (back) into oil or some other stable form. We have enough sunlight to drive the process but it would still have to be cost effective and end up + over the lifetime of the devices and also be economical.
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6. Glenn Tamblyn at 18:19 PM on 11 March, 2012
   Simple question. How do you get someone like Hansen in front of conservative audiences? Won't shift the hard core, but for the many disengaged right-wing, the moderateness of his tone might have an impact.
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7. takver at 19:01 PM on 11 March, 2012
   To answer 5. Jose_X , There was a scientific breakthrough announced in January 2012 regarding an improved method of removing carbon dioxide (CO2) cheaply from industrial smoketacks and even scrubbing the air. Still early stages of research yet, but shows promise. See Alain Goeppert, Miklos Czaun, Robert B. May, G. K. Surya Prakash, George A. Olah, and S. R. Narayanan, Journal of the American Chemical Society - Carbon Dioxide Capture from the Air Using a Polyamine Based Regenerable Solid Adsorbent (Abstract). My article includes a non-scientific description and links to all associated media releases and the article abstract.
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8. Yvan Dutil at 03:14 AM on 12 March, 2012
   @takver The problem with all those techniques is they need energy. Hence this increase the cost. In addition, you have to put the CO2 somewhere. When a train load of coal per day is used in a power station, this is not a trivial issue.
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9. Lazarus at 09:29 AM on 12 March, 2012
   Good vid, I have already done a post on it but concentrating on the 1981 paper he mentions; http://reallysciency.blogspot.com/2012/03/what-hansen-et-al-got-right-decades-ago.html
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10. Riduna at 10:53 AM on 12 March, 2012
    I agree with Hansen's conclusions Does anyone disagree - and if so, why?
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11. chriskoz at 13:05 PM on 12 March, 2012
    Agnostic @10, Does anyone disagree? Is it the rhetoric question, especially given the opinions of commenters 1-9 before yourself? I can perhaps say that James' suggestion of 5m of SLR in this century is a bit exaggerated. Technically, it will be less than a metre until 2100. But uncertainties of upper limit are huge. It may well be that we are already committed to 5m+ if not in 2100, certainly in equlibrium a few centuries later. That's still a moment on an athopogenic scale. So I don't blame him for that.
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12. John Russell at 10:41 AM on 14 March, 2012
    I accept all that Hansen says. I just don't get the scientists who understand what Hansen understands and yet can play down the probable outcome and what it might mean, in practice, for their descendants. It says it all that the first line of Nasa's mission statement was deleted, never to appear again: "To understand and protect the home planet".
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13. jzk at 20:58 PM on 5 April, 2012
    John @12, "I accept all that Hansen says." How about when he says that our Oceans will begin to boil? "you can get to a situation where, it just, the Oceans will begin to boil..." http://www.youtube.com/watch?feature=player_embedded&v=1uxfiuKB_R8#! @2:05.
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14. Daniel Bailey at 21:14 PM on 5 April, 2012
    Jzk, the operative word Hansen uses is "can" (and please refer to the video in its entirety for context, not a solitary quote-mine). This is predicated on many variables also occurring, like first burning all the coal and then exploiting all the tar sands and shale oil extraction technologies and a methane/clathrate permafrost release. Note that the likelihood of this last is sharply confirmed here. Further discussion of those factors belongs on one of the many more relevant threads devoted to those topics, rather than this one.
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15. jzk at 21:19 PM on 5 April, 2012
    Daniel @14, Notice that Hansen begins his talk with "if we allow emissions to continue at a high rate..." Then he gets to talking about losing every species on Earth, and boiling the Oceans. Since all signs point to emissions rates increasing from where they are now (China and India), then according to Hansen these outcomes are real possibilities. This thread is entitled "James Hansen's motivation" and I was responding to a post that stated "I accept all that Hansen says." So how could my post possibly be off topic?
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    Moderator Response:

    [DB] "So how could my post possibly be off topic?"

    Again, reading my comment it is clear that I was referring to the individual factors Hansen discusses, like a methane/clathrate release. Those are best discussed further on individual threads devoted to them (Search function). Please desist in looking to quote-mine and take things out of context.

16. scaddenp at 10:49 AM on 6 April, 2012
    Can anyone point me to any actual paper on whether we can get runaway greenhouse if used all the carbon? I'd like to see the math.
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17. Tom Curtis at 13:59 PM on 6 April, 2012
    scaddenp @16: A Study on the “Runaway Greenhouse Effect” with a One-Dimensional Radiative–Convective Equilibrium Model, by Nakajima, Hayashi, and Abe. Journal of Atmospheric Sciences, 1992. And here is a popular explanation by Chris Colose.
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18. Tom Curtis at 14:09 PM on 6 April, 2012
    I should probably add, the theory is that there is an upper limit on the greenhouse effect which represents the effect of an atmosphere with the maximum saturation with H2O. If the outgoing longwave radiation for a fully saturated atmosphere is greater than the incoming solar energy, in the Earth's case 255 W/m^2 on current albedo, then temperatures will stabilize before full saturation is reached, and hence before the oceans boil away. As it happens, the outgoing limit is significantly greater than 255 W/m^2. Nakajima et al calculated an upper limit of 385 W/m^2, which is approximately 40 W/m^2 higher than the Earth would recieve with an albedo of 0, an unlikely condition with a water saturated atmosphere to say the least. There is some doubt as to the upper limit which must be calculated using models, but it is sufficiently high that it is unlikely that the Earth could reach a runaway greenhouse effect on current solar activity. Of course, if models are as unreliable as is suggested by deniers, then we can have no confidence that a runaway greenhouse effect is impossible. The price of denying science is uncertainty, and that price is paid logically by considering even the most extreme possibilities as on the cards if we continue the grand experiment with the atmosphere. Of course, that would require consistency from the deniers, which is too much to ask.
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19. scaddenp at 14:32 PM on 6 April, 2012
    Thanks Tom, Chris concludes with: " it's worth mentioning that it is virtually impossible to trigger a true runaway greenhouse in the modern day by any practical means, at least in the sense that planetary scientists use the word to describe the loss of any liquid water on a planet." Hansen is saying that with all carbon burnt and presumably with rapid clathrate melt to CH4 not CO2, then it is possible to boil the ocean. While sobering if true, I would be fairly sure his motivation are mostly based on the very considerable damage that would result from far less CO2. I think we should be mostly worrying about the damage from burning the available economic coal.
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20. jzk at 20:16 PM on 6 April, 2012
    Tom @18, The talk starts out "what would happen if emissions continue to grow?" (-snip-) So is it then, a fair statement to say that Hansen's views are "outside the consensus?"
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    Moderator Response:

    [DB] As noted earlier, and as specifically pointed out to you by Tom Curtis below, Hansen does not discuss the runaway greenhouse effect in the video linked in the OP. Your intransigent insistence that he did is therefore utter, willful falsehood.

    Please note that posting comments here at SkS is a privilege, not a right. This privilege can and will be rescinded if the posting individual continues to treat adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

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    Fabricated quote and trolling statements snipped.

21. Tom Curtis at 22:02 PM on 6 April, 2012
    jzk @20, Hansen does not discuss the runaway greenhouse effect in the TED video which this post is about. Therefore discussion of it is off topic on this thread, and your attempts to suggest that because John Russell (@12) agrees with what Hansen says on that video he is therefore committed to agreeing with anything Hansen has said anywhere are trolling, pure and simple. However, for the record, let me state that: 1) You are misrepresenting Hansen in that he clearly indicates that the prospect of oceans boiling only follows "in the long run" and "over centuries" of continuing high emission rates (1:15 fwd on the video to which you linked). Thus it is clearly not an imminent prospect, and is only achievable (on his opinion) by a determined, suicidal continuation of BAU as temperatures rise beyond Eocene levels. Make no mistake that such a continuation would be suicidal. Hansen is probably wrong about runaway greenhouse effect, but if we push tropical sea surface temperatures above 50 degrees C, the fact that the oceans aren't boiling will be purely academic in terms of our prospects of long term survival. 2) When NASA planned the grand tour of Voyegers 1 and 2, they used a model. That model was not evidence, but neither was it guess work. It was the prediction of a well confirmed theory. Climate models are also the predictions of well confirmed theories. Because of the complexity of the situation being modeled, they cannot be solved algebraicly, but instead must be solved numerically using approximations for some factors. That introduces uncertainty, but does not change the results into simple guess work. When you cavalierly dismiss model outcomes, you are in effect insisting that a number of well confirmed empirical theories are false. 3) Hansen's view is that the equilibrium climate sensitivity is 2.8 C per doubling of CO2. The equilibrium climate sensitivity does not include slow feed backs such as the change in albedo due to the melting of ice sheets. Hansen considers the Earth Climate Sensitivity, ie, the sensitivity including all feed backs to be around 6 degrees C. There is no contradiction between that position and that of the IPCC, and indeed, that result has been confirmed from observations by Dana Royer and his associates. 4) Hansen's position on runaway feed backs is not the consensus position. The consensus position in science is not a mandated position required as a condition of doing science, but a common position arrived at by each scientists independent assessment of the evidence. It is therefore no surprise that on some issues there is disagreement. Finally, as noted this discussion is of topic. Therefore if you care to respond, would you please do so in threads on which the response is on topic. For discussion of the the runaway greenhouse effect, I suggest the comments on the article by Chris Colose linked at 17 above. If you comments are about Hansen's views on the runaway greenhouse effect, he has no official spokesperson here so take it up with Hansen.
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22. michael sweet at 22:06 PM on 6 April, 2012
    jzk, It is not a fair statement to suggest that Hansen is "outside the consensus". Hansen suggests that a runaway greenhouse is possible on Earth. Most of what I have seen disagrees with Hansen, see Tom's links above, but that does not mean Hansen is wrong. There does not appear to be a strong consensus on this item. Most scientists currently focus on the near term, say the next 200 years. After that there is less research. Hansen is on one extreme but that does not qualify as "outside the consensus" Re Hansen's discussion of 6C per doubling of CO2. This is the long term, not the short term sensitivity. Hansen agrees with the consensus that the Charney sensitivity is around 3C per doubling. This is the short term sensitivity. Long term, as the ice sheets melt, scientists agree that the sensitivity is greater. Hansen estimates the long term sensitivity, including albedo changes is double the Charney sensitivity. I have not seen comparable estimates from other scientists. Since scientists agree the long term sensitivity is higher than the Charney sensitivity Hansen is firmly in the consensus here. Hansen takes the view that we are responsible for our long term consequences, not just the problems predicted for the next 90 years. Do you care about the world your descendants will have to live in in 500 years? Most deniers do not even care about their children. Go to RealClimate and read their analysis of the temperature predictions Hansen made in 1981. He was 30% lower than actual increases that have been measured. Perhaps he is low here again. The main stream media gives big press to non-scientists and deniers. Hansen is closer to the consensus than Lindzen is. Uncertainty cuts both ways. Hansen's fear of runaway warming may be right, he has a long record of being correct in the past.
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23. John Russell at 02:57 AM on 7 April, 2012
    The latest thoughts from Jim Hansen in the run up to him being awarded, next Tuesday, the prestigious Edinburgh Medal for his contribution to science. Quote:

    "In his lecture, Hansen will argue that the challenge facing future generations from climate change is so urgent that a flat-rate global tax is needed to force immediate cuts in fossil fuel use. The latest climate models had shown the planet was on the brink of an emergency. He said humanity faces repeated natural disasters from extreme weather events which would affect large areas of the planet. "The situation we're creating for young people and future generations is that we're handing them a climate system which is potentially out of their control," he said. "We're in an emergency: you can see what's on the horizon over the next few decades with the effects it will have on ecosystems, sea level and species extinction."

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24. michael sweet at 08:37 AM on 7 April, 2012
    jzk, "The recipient of the 24th Edinburgh Medal was announced today as Dr James Hansen", see above link. If Hansen did not generally agree with the consensus he would not have received the Edinburgh Medal. Where he differs he is often correct.
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25. scaddenp at 09:58 AM on 7 April, 2012
    As far as I can see, there is no consensus on runaway greenhouse to be discussed. Hansen mentions the extreme case of putting every bit of available carbon into the atmosphere,(and its a mighty distraction to real problem of what we are actually doing frankly, on which there is a consensus) and as far as I can see, there is no published science for that extreme case. He may be right (he has the wherewithall to do the maths, unlike me) but we need to see the maths to know. I think its a massive distraction because I doubt you could find an economically justifiable way to achieve it even without the downsides.
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26. Tom Curtis at 11:52 AM on 7 April, 2012
    jzk @20, to correctly quote Hansen what you should have written is:

    "[0:10] If we allow emissions to continue at a high rate, then this century we are going to see ice sheets disintegrate [...] [1:16] On the long run, if that really happened, over the centuries we could get a run away green house effect, and then, that's it for all the species on this planet."

    (Source)

    "[2:04] [The runaway greenhouse effect] means once the planet gets warmer and warmer the oceans begin to evaporate, and water vapor is a very strong greenhouse gas - even more powerful than carbon dioxide. So you can get to a situation where it just ... the oceans will begin to boil and the planet becomes so hot that the ocean ends up in the atmosphere."

    (Same source.) In contrast, your "quote" got the wording wrong, in several places significantly wrong. What is worse, it covered up not just a change in paragraph, but a change in section by an ellipsis which indicated the continuation was part of the same sentence. (This is worse only because your changes of wording did not significantly change meaning.) Further, you did not clearly indicate either the source video, nor the times things where mentioned. More substantially, by not quoting the first part of the section from which the major part of the quote was drawn, you made it obscure that Hansen is talking about high emission rates over the centuries. From your butchered quote, it was quite possible that he was talking about high emission rates over this century only which would have unstoppable knock on effects several centuries down the track. Your immediately following comment encouraged this interpretation. You emphasize that he is puts no limitation on the prediction, and say that, "He is telling the public that if we continue business as usual (as he has said many many times in many places) that very severe things will happen like huge sea level rises, mass extinction events and boiling the water on the planet." Hansen believes that BAU over just this century, indeed, over just the next 50 years will result in huge sea level rises and major extinction events. By just tagging "boiling the water on the planet" onto the list, you implicitly suggest that the timeframe of BAU needed to boil the water is of the same order as that needed for melting most of the West Antarctic Ice Sheet and the Greenland Ice Sheet, ie, 50 to 100 years. Given the butchered nature of your quote, this constitutes a misrepresentation of Hansen. What you should have written is something like:

    "He is telling the public that if we continue business as usual (as he has said many many times in many places) that very severe things will happen like huge sea level rises, mass extinction events and, if continued over centuries, may result in boiling the water on the planet."

    (Amendments underlined, minor amendments for grammar not noted.) That then fairly represents Hansen's views by both by indicating the relevant time frame of BAU needed, and indicating that Hansen believes that the runaway greenhouse effect is a possibility, not a certainty under those conditions (as indicated by his use of the term "could"). I accept that your misrepresentation was entirely unintentional. Indeed, being fair your wording suggests the misrepresentation rather than explicitly stating it. However, I also believe my interpretation of your words to have been entirely justified given what you actually wrote. Note: I am only responding on this point because claims of misrepresentation, or actual misrepresentation must be fairly dealt with where they occurred. Any future discussion of Hansen's views on Runaway Greenhouse should be shifted to where they are on topic.
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27. Tom Curtis at 11:56 AM on 7 April, 2012
    scaddenp @25, can I suggest as a participant (not a moderator) that all future discussion of the runaway greenhouse effect be moved to this post where it is on topic. The OP here is about Hansen's motiviation, and the TED video embedded in the OP, which contains no discussion of runaway greenhouse.
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    Moderator Response: [DB] Thank you. Participants interested in discussing the "runaway greenhouse effect" please do so at the thread recommended by Tom.
28. BillEverett at 04:13 AM on 5 November, 2012
    In his TED talk, Hansen showed graphs of temperature, carbon dioxide, and sea level during the Paleocene. He did not show the methane graph. He said (1) that carbon dioxide lags temperature by a couple thousand years; (2) that deniers use this fact to allege that warming increases carbon dioxide, not vice versa; (3) that, the climate change is in fact initiated by orbital changes [Milankovitch theory] and is accelerated by positive feedbacks, which include carbon dioxide released from the warming oceans as from a warming Coke. In contrast to carbon dioxide, methane leads temperature by about a thousand years in the Paleocene record. It would therefore seem that atmospheric methane was the initial accelerator of climate change and that the later increase of carbon dioxide included not only carbon dioxide coming out of solution in the oceans but also methane oxidized to carbon dioxide in the upper atmosphere. Carbon dioxide levels comparable to current levels are essentially nonexistent in the Paleocene record (industrial emissions of carbon dioxide did not exist then). We face a reasonable probability of major methane releases from thawing permafrost and from benthic methane hydrate desposits. For me, this adds to the urgency of Hansen's admonition.
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29. scaddenp at 09:24 AM on 5 November, 2012
    Bill, can you clarify please? Paleocene is 55-65myr ago. No methane proxy. Can I assume you mean Pleistocene? Carbon isotope studies have looked at methane signature in ice bubble data. Indications to date are that methane source is not benthic hydrates nor boreal peatland(eg Petrenko et al. (Follow cites for other studies). Less consensus on what the methane sources actually are (swamp, burning, lakes etc).
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