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From blog to Science

Filed under: — gavin @ 13 February 2011

There is a lot of talk around about why science isn’t being done on blogs. It can happen though, and sometimes blog posts can even end up as (part of) a real Science paper. However, the process is non-trivial and the relatively small number of examples of such a transition demonstrate clearly why blog science is not going to replace the peer-reviewed literature any time soon.

Way back in April 2005, I wrote a post on RC on the role of water vapour in the greenhouse effect and why it is considered a feedback and not a forcing in the IPCC sense. It was a basic enough exposition, and in lieu of finding a comprehensive paper on the components of the atmospheric greenhouse effect, I did a few very simple (even simplistic) GCM experiments to show what I was talking about. The bottom line was that CO2 was indeed an important contributor to the present day greenhouse effect, and depending on how you calculated the percentage, could account for between 9 and 26% of the effect.

This proved useful, and soon the page was being quoted quite widely. But the calculations were not very sophisticated and I started to be concerned that they were being given more credibility than they deserved – not that they were necessarily wrong (they weren’t), but because a blog post doesn’t give enough context. For instance, some people incorrectly thought that the range 9-26% was the uncertainty in the calculation, rather than two different conceptual estimates. So I started to look for ‘proper’ references for these kinds of calculations.

I had already seen a few papers that calculated the importance of water vapour, CO2 and clouds for a one-dimensional standard ‘profile’ (Ramanathan and Coakley, 1978 for instance), and I was pointed to a section in Kiehl and Trenberth (1997) that turns out to be the most useful reference. They too had used a single ‘typical’ profile. Both of these references (and a few others – like Ray Pierrehumbert’s 2007 paper which used the NCEP global distribution of water vapour and temperature) generally calculated the importance of CO2 in one of two ways – either by looking at what happened when you removed CO2, or by looking at what happened when only CO2 was operating (though rarely both) (because of the spectral overlaps between the different absorbers, the second number is always larger than the first). Invariably, the treatment of clouds was highly simplified or neglected.

What I didn’t find was any justification in the literature for the most widely quoted ‘contrarian’ view of the issue that CO2 was ‘only 2%’ of the effect. I traced this back to a book review that Lindzen wrote about the first IPCC report, but never found any actual reasoning in support of this.

So in putting together a real paper there were a number of necessary steps that went beyond what was appropriate for a blog post. First, the previous literature had to be collated and their results reported in a consistent way. Second, there were a number of differences between the more serious calculations done for the paper and the calculations done casually for the blog. We used a longer period of time (a full annual cycle rather than a single time step) to avoid a bias towards a particular part of the year. Then we rechecked that the radiation code was still giving good results at very low CO2 levels…. and it turned out that it wasn’t – and so we needed to update the code via comparisons with a more complete line-by-line model so that all the tests we were doing were within the validated range of the radiative-transfer code. Finally, we did many more tests – more combinations, different baselines – to try and ensure that the results were robust.

When it came time to submit the paper, we first tried pitching it to BAMS as a popular science piece that would try and explain the concept and clear the air (so to speak). However, for various reasons this didn’t work out (two rounds of unsatisfying reviews). I’d say it was mainly due to the draft not really being pitched at the right level for BAMS. One amusing aspect of the process was that one of the referees initially suggested that our paper wasn’t necessary because it was common knowledge that the attribution to CO2 was between 9 and 26% (sound familiar?). As it turns out, they were reading a page from UCAR which was quoting (without attribution!) from my original blog post.

There was one other interesting (and highly critical) review which objected to the criticism of Lindzen’s 1991 comment, though it is perhaps worth noting that they considered the 1991 comment to be ‘formally incorrect’.

After a period in which I was a little tired of the whole exercise (it happens), we then submitted the paper to JGR, where it had an easier passage. At the same time, the simulations we had done for the paper were also used as part of a broader paper that Andy Lacis wanted to put together for Science. Both these papers appeared in October 2010 – some five years after the initial post, 3 and a half years after the first journal submission, 5 rewrites and 11 reviews.

So why bother to turn ideas from blog posts into real papers? Well, first off, you get to do a much more thorough job. You have the time and space to check multiple variations of the method, and you can take the time to do a proper literature review. And because you have put more effort into it, it is rightly seen as more credible. It’s worth noting that in our case the paper benefited from comments from all reviewers (even the very critical one) – language was tightened up, a broader literature search was done, concepts were clarified and many of the additional issues raised were dealt with.

In turn, the more credible work on the topic forms a stable point around which to craft a critique (if desired), and hopefully provides more of substance to critique (versus a series of blog posts that can be laced with distracting commentary, conceptual errors and moving targets).

To be clear, it is not only the reviews by peers that makes a peer-reviewed paper better than a blog post. Since it is known ahead of time that there is an effort required to get past the peer-review hurdle, the resulting work is usually more reflective, more interesting, more concise and more of a serious contribution – even before it gets to the editor.

Thus when scientists who find themselves criticised in the blogosphere quite often ask their critics to submit their points for peer-review, the point is not to dismiss a critique, but rather to encourage the critics to make the critique as well formulated and a propos as possible. This doesn’t always work of course, but is it nonetheless worthwhile. The alternative, especially for high profile issues, is to try and deal with a multi-headed hydra of critiques that range from the ill-informed to the excellent. Unfortunately, technical commentary does not work well at the ‘speed of blog’ and conversations often take a personal turn (which only rarely happens in the literature).

The many existing critiques of peer review as a system (for instance by Richard Smith, ex-editor of the BMJ, or here, or in the British Academy report), sometimes appear to assume that all papers arrive at the journals fully formed and appropriately written. They don’t. The mere existence of the peer review system elevates the quality of submissions, regardless of who the peer reviewers are or what their biases might be. The evidence for this is in precisely what happens in venues like E&E that have effectively dispensed with substantive peer review for any papers that follow the editor’s political line – you end up with a backwater of poorly presented and incoherent contributions that make no impact on the mainstream scientific literature or conversation. It simply isn’t worth wading through the dross in the hope of finding something interesting.

In the end of course, the science will win out. No single paper is ever the last word on an issue, and there are always new approaches to try and new data to assimilate. But the papers will endure long after the plug has been pulled on a blog. I certainly think that blogs can be of tremendous value in bringing up more context and dispelling the various mis-apprehensions that exist, but as a venue for actually doing science, they cannot replace the peer-reviewed paper – however painful that publishing process might be.

207 Responses to “From blog to Science

  1. 101
    Bryson Brown says:

    The trouble with Feyerabend’s work is that it’s chiefly a reductio of what’s been called the ‘received view’ of how scientific evidence works, and his history of science (e.g. his treatment of Galileo) is sloppy. The point is purely negative, and he offers no richer epistemological framework in which to understand the success of science. That the received view was mistaken is generally accepted. That this implies ‘method’ in science is unimportant and/or that any methodological constraints must be too constraining for good science is not.

    Epistemology of science is tough sledding, but the Galileo stuff is nicely answered by, inter alia, Philip Kitcher, in The Advancement of Science: reliable independent agreement on the results of telescopic observations was quickly established as the use of telescopes spread and the technology improved. Feyerabend’s account is essentially a rhetorical defense of the deniers of that age– clever, and instructive in how it presses for a more careful account of why Galileo’s side deserved to win the debate, but wrong in the (all too familiar) claim of epistemic equivalence between the two sides.

    The key question is, do we have the means to arrive at (always pro-tem) independent agreement on some questions? Science has developed a wide range of methods, in different areas of inquiry, for achieving such agreement– refined methods of observation (look at the history of astronomical observations), development of reliable principles of inference connecting different observations (look at Cuvier’s inferences from partial skeletons to whole organisms and their taxonomic relations) and the identification of the limits of such inferences (from theoretical to simple empirical grounds– and the ongoing interaction between identified failures and other inferences (consider Darwin and Wallace’s inference from the failure of exponential population increase to the existence of selective presssure).

    In climate science there are lots of constraints on what is tenable, from present observations to paleoclimatology to basic atmospheric physics. The science progresses as the constraints are tightened and the range of tenable views narrows. But, for this outsider at least, the explanatory coherence of the current state of the art is strong enough that only dubious speculations about unidentified negative feedbacks provide any hope that the consequences of ongoing GHG emissions will not be unacceptably severe– and that’s in purely climatological terms, setting aside ocean acidification and other risks altogether. Could anyone really want to bet our children’s futures on such speculations?

  2. 102
    Didactylos says:

    TimTheToolMan: even if someone doesn’t supply all the context for something, if they tell you where to look then actually going to look is the very least you can do.

    What is it about blogs and the desire to copy all information everywhere inline? There are limits beyond which it becomes ridiculous. Some sites do it to the point of copyright violation. Excerpts are nice, but not a god-given right. A citation is sufficient.

    And the really amusing thing about this is that I read back through the comments, and TimTheToolMan’s original complaint was simply that he didn’t like or believe the 2% figure. The subsequent twisting and squirming is purely a result of an inability to face the facts.

    Tim, if no reference were given, you would have grounds to complain. But it’s right there! Then M at #30 quoted from it because you seem disinclined to get yourself to a library. And you still aren’t happy!

    I’m going to go out on a limb here, and suggest that nothing will make you happy, since fitting denial and reality together results in a painful dichotomy.

    But in the larger picture, this is a severe limitation of blog science: the need or tendency to limit everything to what is not only freely available, but which is available instantly online. It’s nice that in these connected days, so much is available online. But ignoring the rest or going on petty rants about it – that’s just tiresome.

  3. 103
    Edward Greisch says:

    91 jim: Ethics: 92 Ray Ladbury is correct: \falsifying or denying evidence is actually a mortal sin to a scientist. And of course, there is the 100% certainty that if you falsify data–especially data with any importance, YOU WILL GET CAUGHT.\
    Particular methods are details. The scientific method is that evidence is experimental. That means we don’t rely on ancient texts or human witnesses. It doesn’t matter who legend says wrote it, an old book is not evidence. \Scientific experiment\ is defined. It has to be \public\ and \replicable.\ Revelations that happen inside one person’s head are called hallucinations. Hallucinations are not public and replicable.

    [Response: Edward, no offense, but what are you talking about?–Jim]

    That is how science differs from all previous methods of deciding. Science split away from religion by dismissing ancient texts in favor of repeatable experiments and measurements that everybody could see and do. You DO science. That is the democratizing effect of science.

  4. 104
    Septic Matthew says:

    99, raypierrre, in comment: People are certainly tired of hearing about my book

    Not I. I rush or amble to your book and read the sections that you alert me to in these dialogues.

  5. 105
    Septic Matthew says:

    102, Didactylos: nothing will make you happy

    That is true of me, though not aimed at me. I expect the next 10 years to be excruciatingly suspenseful as I watch the unfolding of new developments in energy supplies, reduction in coal use, new developments in flood control and irrigation, the ebb and flow (so to speak) of the arctic ice cap, and as I gradually accumulate evidence about which forecasts of the future are more accurate. I do not expect that my views of AGW will lead me to happiness at all.

  6. 106
    Mark A. York says:

    Thanks, Ray. Done.

  7. 107

    99, raypierrre,

    People are certainly tired of hearing about my book…

    Actually, I’m eager to buy it, and every time you mention it I guiltily remember that I haven’t yet (and who am I to contribute much of an opinion until I have?).

    Maybe in a month or two the swamp of life/work/distractions will give me the time I need (anyone know what this week’s winning lottery numbers will be?).

  8. 108
    Geoff Beacon says:

    Bryson Brown #101

    The trouble with Feyerabend’s work is that it’s chiefly a reductio of what’s been called the ‘received view’ of how scientific evidence works…. The point is purely negative, and he offers no richer epistemological framework in which to understand the success of science.

    Would you say that Gödel’s point was “purely negative”?

    The key question is, do we have the means to arrive at (always pro-tem) independent agreement on some questions?

    Who’s the “we”?

    I don’t think the current peer-review methodology, which some seem to equate with scientific method, answers the questions we need answering now.

    only dubious speculations about unidentified negative feedbacks provide any hope that the consequences of ongoing GHG emissions will not be unacceptably severe

    But we can engineer negative feedbacks – that’s called geo-engineering. But until that gets going we need to slow global warming as much as possible. That means taking short term forcing agents seriously and reducing black carbon and methane emissions (as well as CO2 emissions). Remember the positive feedbacks are temperature driven and only indirectly CO2 driven.

    Could anyone really want to bet our children’s futures on such speculations?

    Like the Trillion Tonne Speculation? This seems to assume the “safe” level of a 2º C rise in global temperatures will occur only after a trillion tonnes of carbon are emitted. If its climate models underestimated or omitted positive feedbacks that are possible it is wishful thinking … unless there are unidentified negative feedbacks.

    P.S. Are these feedbacks missing from the Trillion Tonne Speculation?

    Spielhagen et al. “Enhanced Modern Heat Transfer to the Arctic by Warm Atlantic Water

    Zaehle et al. “Terrestrial nitrogen feedbacks may accelerate future climate change

    Flanner et al. “Radiative forcing and albedo feedback from the Northern Hemisphere cryosphere between 1979 and 2008

    BBC report “Amazon drought ‘severe’ in 2010, raising warming fear

    [Response: Geoff, can you please drop this? We have discussed uncertainties in sensitivity a dozen times, we have discussed Earth System Sensitivity and we have discussed what the 2 deg guardrail is based on (and that is not a binary safe/dangerous limit). We will no doubt discuss all of these things again. But just not here. Thanks. – gavin]

  9. 109
  10. 110
    Edward Greisch says:

    “Edward, no offense, but what are you talking about?–Jim”


    “Science and Immortality” by Charles B. Paul 1980 University of California Press. In this book on the Eloges of the Paris Academy of Sciences (1699-1791) page 99 says: “Science is not so much a natural as a moral philosophy”. [That means drylabbing [fudging data] will get you fired.]
    Page 106 says: “Nature isn’t just the final authority, Nature is the Only authority.”

    Nature isn’t just the final authority on truth, Nature is the Only authority. There are zero human authorities. Scientists do not vote on what is the truth. There is only one vote and Nature owns it. We find out what Nature’s vote is by doing Scientific [public and replicable] experiments. Scientific [public and replicable] experiments are the only source of truth. [To be public, it has to be visible to other people in the room. What goes on inside one person’s head isn’t public unless it can be seen on an X-ray or with another instrument.]
    Science is a simple faith in Scientific experiments and a simple absolute lack of faith in everything else.

    In the book: “Revolutionary Wealth” by Alvin & Heidi Toffler 2006 Chapter 19, FILTERING TRUTH, page 123 lists six commonly used filters people use to find the “truth”. They are:
    1. Consensus
    2. Consistency
    3. Authority
    4. Mystical revelation or religion
    5. Durability
    6. Science

    Science is the ultimate Protestant Reformation. We went from believing whatever the priest said to reading the bible for ourselves to doing our own experiments. Doing our own experiments actually works. There is another implicit step here. The implicit step is realizing that ancient [stone age to bronze age] people did not have some source of knowledge that we do not.

    I am talking about science in very general terms. Now you have a clue as to why so many people are against science in general. Former beliefs are left out.

    [Response: The original question was just requesting some elaboration on Ray L’s idea that the methods of science are not easily described. Ray and I both did that. You are taking it way off the rails and firing random shots into the air. Please don’t–Jim]

  11. 111
    Chris Dudley says:

    raypierre (#99),

    In his book, Hansen is coming from the direction of the habitability zone. That pretty much means that what he is considering is the loss of oceans when the solar constant is 1.1 times greater than now. And, that ‘threshold’ is based on losing the oceans before the Sun expires in Kasting’s paper. That is different from producing a dry hot surface with all the water from the oceans in the atmosphere.

    Hansen does think he is seeing an increased sensitivity as the Earth warms in the 2005 paper and he considers this important in his book (fig. 30 there) to getting to a pre-Venus configuration using available organic carbon.

    I’m not too sure I see the importance of getting rid of the oxygen leftover from the oceans. It happened on Venus somehow. And, oxygen is not a greenhouse gas. More carbon dioxide will accumulate from volcanoes over time and produce a hot surface with or without the oxygen.

    [Response: If you don’t get rid of oxygen, it recombines with hydrogen and chokes off escape. That in itself further limits the chance of water loss on an oxygenated planet like Earth. On Venus, the slow trickle of oxygen produced by photolysis is hypothesized to have combine with oxidizable minerals in the surface rocks. But Chris, why are you so obsessed with Hansen’s claims regarding the Venus Syndrome. Can’t you find something more plausible to worry about? –raypierre]

  12. 112
    Ron Taylor says:

    Ray #52, I could not agree more. My point was to stick to the peer reviewed science track. That is where the most reliable studies will be found and where needed correctives will surface. It is a process, not a point in time. That is why I trust RC. It generally sticks to the peer reviewed material and is very clear when it goes beyond it.

  13. 113
    One Anonymous Bloke says:

    re: Jim’s inline response at #91. That clarifies things enormously.

    Re Ray Ladbury #92. Nitpicking, but there’s a distinction between an ethic and a moral: the moral of the story is that we adopt these ethics.

    The previous discussion between the two of you, #80 had left me with an impression of the opacity of science to the casual observer, but your subsequent explanations reveal something a lot more transparent – caring and honesty are things that we can all understand – in a way they are “the scientific method”.

    Thank you both for your responses.

  14. 114
    chris says:

    I don’t think the current peer-review methodology, which some seem to equate with scientific method, answers the questions we need answering now.

    Geoff, I can’t imagine anyone “equating” “the current peer-review methodology” with “the scientific method”, nor believing that peer review has very much to say about what we know of the natural world. The peer review method doesn’t “answer questions” (about the physical environment). It provides a check that science which is disseminated via the scientific literature has a good chance of according to standards of quality.

    Surely it’s the role of science (the collective effort of scientists and perhaps the wider society that decides which issues should be subject to particular scientific focus) to “answer questions”. One might question whether the state of our scientific knowledge is sufficient to answer “questions we need answering now”, but we can’t really say unless you are more specific about which questions (you consider) need answering now.

    Of course science can’t answer questions like “..are there unidentified negative feedbacks?”. That’s a question mired in illogic. That’s not to say that science might not identify as yet unidentified negative feedbacks at some time in the future. On the other hand scientific knowledge (analysis of past temperature responses to enhanced radiaive forcing) indicates that that’s likely to be wishful thinking (a low probability likelyhood). Science can be quite helpful when questions are well framed.

    [Response: While one cannot strictly rule out that some climate entirely different from any studied in the past might have unidentified negative feedbacks, the study of paleoclimate very strongly argues against such feedbacks. Uncertainties in paleoclimate reconstructions somewhat limit ones confidence in that statement, but there is no question that science, through improved reconstructions, can address the question of unidentified negative feedbacks. –raypierre]

  15. 115
    Chris Dudley says:

    raypierre (#99),

    Concerning weathering in a warm climate, I notice that you in 2002 wrote this in Nature:

    “A distinct change in regime occurs when the evaporation exceeds
    the absorbed solar radiation (Fig. 4), by which point the surface has
    become colder than the overlying air. Past this point (about 302 K in
    the high-CO2 case), precipitation increases more slowly with
    temperature. Without the destabilizing effects of water vapour
    buoyancy, evaporation is limited to a value only slightly in excess of
    the absorbed solar radiation. In this case the silicate–carbonate
    weathering thermostat breaks down, as increases in temperature fail
    to increase precipitation (for a fixed solar brightness) and so cannot
    halt accumulation of CO2 in the atmosphere.”

    I had earlier discussed the air being dry up to about 25 km in one of Kasting’s models as an impediment to weathering. You later invoked ‘weathering’ within the oceans themselves as a new thermostat. I would like to know more about this idea. Essentially, any chemical process is going to leave a layer of silica that might impede further processing. There should be a layer of limestone as well. Can this new mechanism handle the required quantity of carbon dioxide without being shut down by its own success? Normally, weathering involves vastly increasing the surface area available to react with atmospheric carbon dioxide through the freeze-thaw cycle and water erosion. This would not be the case below the surface of the ocean.

  16. 116
    TimTheToolMan says:

    “Calm down and take the time to study “The Discovery of Global Warming” by Spencer Weart:”

    Calm down? I think I have the right to question claims made about what other people say to discredit them. And I’d expect them to be able to back up those claims.

    At the moment, we have Gavin using the Lindzen quote of “about 2.5C” atmospheric warming attributable to CO2 and expecting that to somehow justify the 2% mentioned in the article.

    However 2.5C out of the 33C that is frequently accepted as the amount GHGs warm our atmosphere is closer to 7.5% and not so far from Gavin’s own calculated value at the low end of his range of 9%

    So how does the 2% relate? Well without the context within which it was made we’ll never know for sure whether it was with respect to anthropogenic CO2 or not. If it was, then Lindzen is in the ballpark his statement and misquoting or more accurately misinterpreting him would be wrong.

    [Response: There are two different numbers here. The first is the ‘2%’ (or even ‘1%’ in the House testimony). Under no circumstance is this close to ‘9%’ (which in any case got revised in Schmidt et al (2010) to 14% because of the re-calibration of the radiation code). There remains no justification for the 2% number in any published source that I have been able to find. As for the ‘2.5deg C cooling’ from zero CO2, this is not even a written statement, it being an off-the-cuff answer to a question. Given the radiative forcing from zero CO2 with respect to present-day of something like -28W/m2, this implies a climate sensitivity of 0.33 deg C for a doubling of CO2! – a number so low that not even Lindzen has suggested it explicitly. Yet you want us to take seriously unsupported, and frankly impossible, claims and put them on the same footing as real research. Oh please. – gavin]

  17. 117
    Hank Roberts says:

    > we’ll never know for sure
    ‘We must know — we will know!’

  18. 118
    Edward Greisch says:

    You are taking it way off the rails and firing random shots into the air. Please don’t–Jim]

    No I’m not. I’m getting back to basics. I understand that you see a sensitive subject. OK. No more sensitive subject.

    [Response: Not so much sensitive, but way too deep into philosophy for the present thread. I did get into some of these issues way back in my Darwin post, where the question of how to distinguish science from non-science arises, but this does push the limits of expertise of any of us here at RealClimate — except in the sense that any practicing scientist develops a sense of what is and is not science. –raypierre]

    [Response: No Edward, it’s not an issue of sensitivity in the least. The topic/question we were discussing was about methods scientists use in doing their jobs–not all the things you started bringing up.–Jim]

  19. 119
    Dave says:

    Gavin – TtTM doesn’t want you to take anything seriously. He just wants you to waste your time. Every time he comes back here, it’s the same game; obfuscate, confuse, and consume precious resources.

    Bore hole.

  20. 120
    Isotopious says:

    Preindustrial CO2 = 280ppm
    Current CO2 = 390ppm
    Therefore, Manmade = 110ppm, Natural = 280ppm
    Of Low estimate of CO2 contribution = 9%, Manmade = 3%, Natural = 6%.

    This is an interesting discussion, because the 6% could be a slow feedback due to some other aspect of the system, such as the hydrosphere.

    There is the possibility that water vapour AND the natural CO2 are both in fact dependant on some other planetary imbalance.

    As far as I know, Lindzen’s argument is that the planet’s climate is never in balance (not a bad assumption given that there is very strong evidence that climate changes in the absence of humans).

    On the other hand there is Gavin’s argument, that water vapour is a feedback most likely due to CO2…(but that would suggest a minor role for internal variability, leading to debate over the magnitude of past changes, external forcing, Holocene stability, hockey sticks, etc..

    [Response: Despite the fact you appear to be agreeing with me on something, this isn’t right. The climate can be close enough to being in quasi-equilibrium for concepts like equilibrium sensitivity to hold. That means that for quite long time periods the planet can stay very close to radiative equilibrium – i.e. the Holocene (until recently), or the last glacial maximum. If this was not the case, the resulting TOA heat fluxes would have caused dramatic temperature and sea level changes – thus have observed periods without either, one can conclude that equilibrium can be a reasonable working assumption. This has nothing much to do the degree of internal variability (which is multiple in the presence of strong feedbacks in any case). – gavin]

  21. 121
    Phil Scadden says:

    Chris Dudley, my understanding of the weathering thermostat has nothing to do with rocks reacting with air. CO2 dissolved in water weathers the rock releasing cations esp Ca++. Once washed into seawater, Ca++ changes the chemical equilibrium so CaCO3 is precipitated out. Limestone layers only form where this process happens in places with low sediment flux.

    [Response: Not quite. The silicate/CO2 reaction is indeed an aqueous one that takes place primarily when rain containing dissolved CO2 (from the air!) washes over silicate rocks. But it is the the exchange of carbon and silicon, leading to formation of the carbonate, that ultimately takes CO2 out of the air. Where the carbonate (loosely speaking, limestone) ends up in the end is fairly immaterial. The ocean plays no significant role in the silicate weathering thermostat, except as a source of rainfall. –raypierre]

  22. 122
    Chris Colose says:


    Think of it this way. Suppose we ignore all feedbacks and just let the climate system come to equilibrium after some perturbation. The climate sensitivity in this circumstance is 1/(4*sigma*T^3)=0.27 K/(W/m2). Most model estimates estimate the Planck feedback to be roughly this value, or a tiny bit higher ~0.3 K/(W/m2) due to atmospheric absorption. See Table 1 here and raise the numbers to the “-1” power to be consistent with the notation I’m using to verify.

    From Myhre et al (1998), and following from the IPCC AR4 and TAR reports and others, the radiative forcing for CO2 change is ~5.35 ln(C/C_o) where C and C_o are the final and initial concentrations. If we use this equation to say, 20 ppm from pre-industrial conditions of 280 ppm, then RF= -5.35*ln(14)~-14.2 W/m2

    Multiplying this forcing by 0.3 K/(W/m2) gives us around 4-4.5 C decrease in temperature, roughly a factor of two away from Lindzen’s estimate. This is even with 20 ppm of CO2 providing a greenhouse effect, and I only stopped there since the logarithmic approximation breaks down at low concentrations as the center of the ~15 micron feature is not yet opaque as you move into the high atmosphere. Even methane is more in a linear to square root regime forcing-wise, so removing all the CO2 can easily double this back of the envelope calculation.

    Now we throw in a water vapor feedback and ice-albedo feedback. In the Schmidt and Lacis et al, Pierrehumbert, Voigt, etc work the temperature plummets considerably, forcing snowball type scenarios (Lacis didn’t really run the model long enough to see a real snowball equilibrium, but the temperature drops by some 30 C). At 250 K the saturation vapor pressure (with respect to ice) is ~0.8 mb, compared to over 30 mb closer to 300 K, and in a snowball-like regime there’s very little of a water vapor feedback. Of course, when you throw in the albedo feedback, the “33 K” enhancement that the atmosphere maintains is an underestimate. Clouds could conceivably help the situation, especially if they are sitting over a reflective surface, but Lindzen’s “2.5 degrees” is to be blunt, just lying in a testimony.

  23. 123
    Chris Colose says:


    While we’re still (somewhat) on the subject, I was wondering if anyone has attempted to calculate runaway greenhouse thresholds or HZ limits for different solar types, even in a simplified no-cloud response setting? For M-stars at least (assuming tidal locking can easily be rectified as Joshi showed), since the stars emit less UV flux and are generally redder, it would make an atmosphere prone to a lower albedo, but would also seem to make photo-dissociation slower (though I think M-types are a bit more chaotic and periodically emit pulses of high energy, especially in the early stages).

    [Response: See Selsis et al, in ApJ. There is a lot more to be done on this, but they make a very credible start of it. –raypierre]

  24. 124
    Isotopious says:

    The estimates of climate sensitivity are on the record, and they are all over the place. The difference in the estimates is in some cases greater than the estimates themselves.

    Re Lindzen:

    “…this implies a climate sensitivity of 0.33 deg C for a doubling of CO2! – a number so low that not even Lindzen has suggested it explicitly.”

    Give him some credit, .5 deg C is in the ball park, and although LC10 has not been published, he does have some interesting data to support low sensitivity (even you though it was interesting, Gavin).

    To be frank, I think Lindzen is wrong on this one (his estimates are too high).

  25. 125
    Didactylos says:

    So far, despite TimTheToolMan’s protestations, nobody has misquoted Lindzen. Unless he is just trolling, it’s hard to see what there is to get excited about. Isn’t a more germane question “Why is Lindzen dropping various different numbers without providing any context”? He doesn’t appear to provide enough context to even distinguish the figures. Are they supposed to represent the same quantity? Is he just sloppy? Is he making the numbers up as he goes? Where are the numbers from?

    Where’s TimTheToolMan’s outrage? Oh, right. Pointed at his foot.

  26. 126
    Hank Roberts says:

    > all over the place.
    > in the ball park
    > (his estimates are too high)

    Where is your ball park? What game do they play there?

  27. 127
    TimTheToolMan says:

    “which in any case got revised in Schmidt et al (2010) to 14% because of the re-calibration of the radiation code”

    As far as I can tell from your paper “The attribution of the present-day total greenhouse e ffect”, this is an equilibrium figure for the CO2 component and not an instantaneous effect. Basically the 14% figure uses the assumed feedbacks built into the model to arrive at its result.

    [Response: No. There are no feedbacks considered – it is just the change in GHE from removing CO2 with no other change at all. It is assuming equilibrium though. – gavin]

    For argument’s sake, when you do that simulation, where does the temperature start to reduce towards its equilibrium figure from? Is it anywhere near 98%?

    [Response: Temperature is fixed, so I don’t really understand your question. – gavin]

    And…Dave, understanding where people are coming from requires discussion not out of hand dismissal. We could simply ask Lindzen if he frequented this blog…but he doesn’t appear to do so. I’m sure Gavin would simply ignore me if he thought I was simply trolling.

  28. 128
    TimTheToolMan says:

    “Temperature is fixed, so I don’t really understand your question. – gavin”

    Well given its an equilibrium figure, I’m interested in the temperature change at the start of the run rather than at equilibrium. The instantaneous effect.

    Perhaps this is where a 1 or 2% figure can come from.

    [Response: But this isn’t a transient run. Lacis et al (2010) did do perhaps something like you are referring to – removing all CO2 and seeing what happened – and temperatures dropped more than 30 deg C. – gavin]

  29. 129
    One Anonymous Bloke says:

    TtTM #128 “Perhaps this is where a 1 or 2% figure can come from.”

    Perhaps so, but given the wealth of evidence presented so far, of the various figures Lindzen has come up with, off the cuff remarks, unsupported statements to Congress, etc. etc. it seems far more likely that he plucked it out of his ear. None of which explains why you aren’t asking him. here you go, here’s your first step.

  30. 130
    Ray Ladbury says:

    Huh? The climate sensitivity estimates within the past decade have largely been between 2 (or near) and 5 degrees per doubling. Methinks you are talking out of an alternative orifice.

  31. 131
    TimTheToolMan says:

    ” Lacis et al (2010) did do perhaps something like you are referring to – removing all CO2 and seeing what happened”

    Yes, an interesting result.

    From your paper : “Indeed, a model simulation performed with zero CO2 gives a global mean temperature changes of about -35C and produces an ice covered planet (A. Lacis, pers. communication).”

    So given the prevailing view is that GHGs increase the temperature by around 33C they’re saying without CO2, the temperatures decrease to below this value. Snowball earth presumably. My understanding was that Snowball earth might have happened in the past with considerable CO2 present and I do wonder how parameterisation is handled when the climate is so far from what is thought to be understood.

    But back at your paper and trying to work out Linden’s rationale for making his statement, You say “while holding the climate (spatial and temporal distributions of temperature, surface properties etc.) Fixed”

    So what did vary? Clouds? Atmospheric temperature gradients? water vapour within the assumption of a presumably unchanged SST? Stuff like that?

    [Response: Regarding the Snowball, you ought to read some real science and not take your cues from Monkton. There’s a bifurcation in the system. To get into a Snowball, you need to draw down CO2 to very low values. Once you are in, however, the CO2 has to be increased to very high values to get out, because snow/ice reflects 60% or more of the incoming radiation, and so the Earth can remain very cold even with high CO2. The energy budget has two parts you know — absorbed solar radiation and outgoing infrared. As for Lindzen, you’re wasting your time and ours trying to find some justification for his statement. There is no scientific justification for his statement. It’s bunk, and is simply made up in order to mislead people who don’t know better. I find this sad. I’ve known Dick for 30 years, and there was a time when he was still a credible scientist. He’s abandoned that, at least when he thinks he can get away with it. –raypierre]

  32. 132
    David B. Benson says:

    In the January 2011 issue of the Notices of the American Mathematical Society there is a relevant book review and an article which properly ought to be commented upon in an open Unforced Variations thread, but unfortunately there isn’t one just now.

    (1) In 1904 Henri Poincare announced a question which came to be known as the Poincare conjecture on which progress on questions related to this very famous problem happened finally in 1960 and 1982. The conjecture was resolved, in the positive, 99 years after the anouncement by Gregory Perelman in a post to the internet which he subsequently refused to publish in a standard refereed journal. There is more; he turned down the Cray Research Institute’s million dollar prize and rejected his Fields Medal, this being much more prestigous than a mere Nobel Prize despite significantly less media attention. This story indicates the, up to now, extreme rarity of scientific advancement via blog/internet; I opine we’ll see more of it, a form of returning to the communication of science rather more akin to that used in the days before journals. [The book, by the way, is not recommended but the book review itself is of interest.]

    (2) The cover article is entitled Vortices and Two-Dimensional Fluid Motion. To a good approximation the atmosphere and even better the oceans are well approximated via only 2 dimensions. Under quite realistic conditions, a system of many small “random” vortices evolves into a system of a few large ones. Seeing this, well described, helped me to understand how energy can flow from the seemingly more disorganized small scale QPOs in the Pacific, say, to the larger QPOs, such as the PDO for example.

  33. 133
    Salamano says:

    “[Response: But this isn’t a transient run. Lacis et al (2010) did do perhaps something like you are referring to – removing all CO2 and seeing what happened – and temperatures dropped more than 30 deg C. – gavin]”

    I wonder if I should be getting a new textbook for the meteorology classes I teach. Even when I was in school we’ve been going off the idea that if the Earth’s atmosphere was a vapid emptiness that did nothing but served as a conduit to balance the Earth’s energy budget between itself and the Sun, that the average surface temperature would be 0F (-18C) … From what you’re saying, simply removing just the 380ppm of CO2 will be near the same as removing everything else in the atmosphere as well? Are all the other parts-per million in the atmosphere really that insignificant?

  34. 134
    Salamano says:

    [Response: But this isn’t a transient run. Lacis et al (2010) did do perhaps something like you are referring to – removing all CO2 and seeing what happened – and temperatures dropped more than 30 deg C. – gavin]

    I might have to get a new textbook for the meteorology classes I teach. Even when I was in school we were going off the idea that if all the atmospheric contents vanished, and we were left simply with a conduit that allowed radiant energy from the Earth and Sun to balance (heat-energy budget stuff), we’d be left with a planet of an avg. surface temperature of 0F (-18C). From what you’re saying, just taking away the 380ppm of CO2 creates the same effect as removing everything else in the atmosphere along with it. Are all the other components in the atmosphere really that insignificantly negligible?

    [Response: No, we are saying that your calculation of a temperature of -18C without an atmosphere leaves out an important feedback. That calculation is done taking out the greenhouse effect and keeping the albedo constant. Now guess what — the Earth has OCEANS, which FREEZE and get WHITE. So, if you take out the CO2, in fact the albedo increases, you wind up in a Snowball, and it’s even colder. You have multiple levels of confusion here, actually, since taking out the N2 and O2 left when you take out the greenhouse gases has essentially no effect on the infrared opacity of the Earth, though they do have an effect on climate by moving heat around in the atmosphere. The calculation in Lacis et al, described by Gavin, was actually done first by Aiko Voigt (Voigt A, Marotzke J. 2010. The transition from the present-day climate to a modern Snowball Earth. Clim. Dyn. 35:887–905) but given sensitivity to clouds and such, it’s nice to see it reproduced in a separate model. –raypierre]

  35. 135
    Hank Roberts says:

    Y’know, you can read it yourself. Go to your public library.
    Ask them for this:

  36. 136
    One Anonymous Bloke says:

    TtTM: “so far from what is thought to be understood.”

    Um, spot the nonsense. “Understood” by whom, precisely? While you’re at it, who’s doing the thinking of which you speak?

  37. 137
    John E. Pearson says:

    131 Timthetoolman said quoting Gavin’s paper, sort of,

    while holding the climate (spatial and temporal distributions of temperature, surface properties etc.) Fixed

    so what did vary?

    Here’s the actual quote: We use the IPCC AR4 version of GISS ModelE [Schmidt et al., 2006] to calculate the instantaneous changes in radiative fluxes to changes in individual LW absorbers, while holding the climate (spatial and temporal distributions of temperature, surface properties etc.) fixed .

    I’m no climate scientist but I’d hazard a guess that they calculated the instantaneous variation of the radiative fluxes in response to changes in the individual long wave absorbers.


  38. 138
    Chris Colose says:


    I’ll try to amplify on raypierre’s statement, only because I think it’s important, and hopefully it doesn’t come off as me being in a bad mood. I’ve been “taught” about the greenhouse effect in multiple courses over the last few years, and you won’t find a better version than in Ray’s Principles of Planetary Climate. There are some more complete “radiation” books, but I don’t think any rival its application to climate, and it’s very helpful as well to learn about this stuff from someone whose perspective is more on the lines of planetary atmospheres rather than just confining to Earth. It allows generalizations to other situations (such as infrared scattering, antigreenhouse effects, runaways, etc) which aren’t really important in the modern climate but still lend insight into the physics. I’ve actually had several discussions (some debates) and got to play instructor once in a great while just because there’s a lot of subtle details in the greenhouse effect and feedbacks, which for some reason, no one but the experts seem to know (and sometimes they don’t know it, I was recently taught in an upper level climate class that CO2’s absorption at 15 microns was unimportant, it was the 4 micron band that mattered most, though the professor did it right later in the course). It’s especially annoying when you just throw pictures with yellow and red arrows bouncing off an “atmosphere” and a “surface” on powerpoint and say, “here is the greenhouse effect!!” because the explanations are usually wrong on a lot of fundamental levels. Anyway, that’s my rant…

    I don’t know at what level you teach meteorology. If it’s at a basic level with no math, then the canonical explanation of the greenhouse effect goes like “If Earth had no greenhouse effect, it would be 33 C (59 F) colder. N2 and O2 doesn’t contribute, but some of it is CO2, methane, and the trick question to the students…water vapor is actually the most important”

    If you teach at an algebraic level, then you probably balance energy equations such as S(1-alpha)/4=sigmaTe^4, then you solve for Te and say it’s 33 K lower than it should be. Maybe you start adding a bunch of slabs to the air and say the new temperature is (n+1)^1/4 * Te = Ts, where n is the number of slabs (which you can also assign a non-unity absorptivity-emissivity to, and it’s still easy to work out on paper quickly if n is small). (If you actually teach at this level or higher I’d recommend Ray’s book, or even David Archer’s). A lot of people use the slab model, even Archer, and also Hartmann, Marshall and Plumb, etc but I find it physically uninsightful and does not justice to the TOA budget/lapse rate effects critical to the greenhouse effect.

    Here’s the issue…first of all, N2 and O2 DO contribute to the greenhouse effect, even if they don’t absorb infrared radiation, because they broaden the spectral features associated with the GHG’s through collisions. It’s also through these collisions that one can maintain LTE and really define (easily) a local temperature, and one that heats upon when you absorb a photon. Look at Mars, with more than 90% CO2, yet it’s atmosphere is thin enough to make a rather small contribution to actually enhancing the surface temperature above Te.

    Second, Te is just a number you get when you figure out what the solar constant is, and you’re given the albedo. The albedo is not a stagnant quantity; it’s nice to hold it constant for back-of-envelope calculations, but when you actually say the greenhouse effect keeps things 33 K warmer, if you don’t think removing that is going to significantly expand ice cover/snow and change clouds you’re just providing students with a baseline number and something to compare it to that has little practical meaning. The “effective” temperature would certainly not be 255 K if you removed the greenhouse effect.

    Third, unless you’re just teaching this for half of a lecture and never returning to it again, properly diagnosing forcing and feedback factors is absolutely essential to any meaningful discussion of climate. The fact is water vapor is only the most important in the sense that it represents the largest fraction of infrared opacity in our atmosphere, but how the water vapor greenhouse effect is allowed to exist in the first place (because it’s a condensable gas sitting over a reservoir of ocean) is absolutely dependent on the sunlight and the other non-condensing GHG’s. CO2 builds up the framework for the terrestrial greenhouse effect, because removing it allows you to cool down enough to collapse most of the water vapor effect as well.

  39. 139
    One Anonymous Bloke says:

    Re: Ray Pierrehumbert’s response to #131. I’ve been wanting to know more about this (the snowball earth/high Co2 josmiwap) for weeks, and I figured eventually something would come up if I just kept my eyes open. Thanks again. I delight in curious monkeys.

    [Response: Well, if you want to know more about Snowball Earth, your dreams are about to come true. I just got the final page proofs back for my Neoproterozoic review article, due to appear at Annual Reviews of Earth and Planetary Science. The article will be up on the AREPS site in April, and a preprint ought to be up on my own publication site within a week or so. –raypierre]

  40. 140
    TimTheToolMan says:

    “Regarding the Snowball, you ought to read some real science and not take your cues from Monkton.”

    I took my clues from Gavin who had interpreted and possibly quoted from Lacis actually. I even quoted it above. He said…

    “Indeed, a model simulation performed with zero CO2 gives a global mean temperature changes of about -35oC and produces an ice covered planet”

    An “ice covered planet” is Snowball earth isn’t it?

    Also CO2 levels (according to the Wiki FWIW) have our current levels as low as they’ve ever been so I’m not sure where you’re coming from with your comment.

    But regarding Lindzen, whichever way you look at it, he’s still a clever man and has his own views on things. I agree that without papers to back him, he’s on thin ice so to speak and certainly AGWers have parted ways with his beliefs on climate drivers but that shouldn’t stop us from understanding what those beliefs are and where he’s coming from with them.

    Outright attacking them because your models say otherwise is going to be counterproductive to any cause you may have on “convincing people” and not good blogging etiquette at any rate.

    [Response: Well Timtt, some of your comments are so obtuse it’s hard to know what you are getting at, but in the comment I was responding to, you appeared to be raising the same spurious point as Monkton, namely that at some times in the past CO2 was thousands of times higher yet we were in a Snowball Earth (implying that CO2 must not have much to do with temperature). What else was I to make of your statement that “My understanding was that Snowball earth might have happened in the past with considerable CO2 present …” If that was a misunderstanding, and you don’t want to be misunderstood, you ought to try being clearer about what you mean. Even after your “clarification” I really have no idea what you’re trying to get at here. Regarding Lindzen, it doesn’t matter a whit how clever he may be if he makes up numbers for climate sensitivity and provides no physical argument to back them up. It’s not just a matter of “models” disagreeing, except in the trivial sense that every calculation is in some sense a model. And it’s not a matter of our physical argument vs. his since we have a physical argument based largely on the basic physics of radiative transfer, and he has no argument whatever. I think it’s fair game to attack somebody who just makes up numbers and throws them in front of Congress. His views don’t matter a whit if he can’t back them up with physics. For all I know, his views may be based on the idea that the Great Green Spaghetti Monster keeps climate from changing no matter what humans put in the atmosphere. And Tim, I smell some concern trollism coming in there at the end. Your main purpose in life seems to be to not be convinced by anybody about anything nowhere nohow. –raypierre]

  41. 141
    One Anonymous Bloke says:

    re: #138 Dr.Pierrehumbert. I gooScholar searched for “Neoproterozoic” and found some more reading. If I get up to speed I’ll be astonished. Thank you.

    [Response: A terrific place to start is Paul Hoffman’s magnificent Snowball Earth site here. –raypierre]

  42. 142
    TimTheToolMan says:

    “I’m no climate scientist but I’d hazard a guess that they calculated the instantaneous variation of the radiative fluxes in response to changes in the individual long wave absorbers.”

    That seems reasonable but in what sense in a model? Its very unclear from the paper what’s actually happening.

    The paper goes on to say “The climatology is derived from a year-long simulation using ca. 1980 conditions”

    If its instantaneous and nothing is allowed to change (apart from the LW absorbers) then why let it come to equilibrium over a year?

    [Response: It may seem unclear to you, but that’s only because you don’t know how to read, or at least are putting up a good simulation of it. Standard practice would be to run the model, take the state at any given time (temperature. water vapor and cloud fields) then using that, run the radiation model on the field with one constitutent changed (e.g. water vapor taken out, or CO2 taken out, or either one changed in some prescribed way). Standard practice, but you still need a climatological field on which to base the perturbed radiation calculation. Ever hear of partial derivatives? Like where you compute changes varying one thing while holding everything else fixed? –raypierre]

  43. 143
    TimTheToolMan says:

    ” It may seem unclear to you, but that’s only because you don’t know how to read, or at least are putting up a good simulation of it.”

    Read what? I’ve read the paper…I’ve even started on the reference to Schmidt 2006. Maybe its “standard practice” to you but it certainly isn’t to 99.9% of your readers.

    Having said that, thanks for the explanation. So if I understand you correctly you pick a year (and 1980 would seem “nondescript” in that regard, hopefully eliminating biases) where you supply some unspecified conditions for that year (SST and regional temperatures probably, cloud cover maybe? Other things too presumably) and run the simulation using those conditions as input, stopping it every so often and calculating the radiative flux as a result of removing the LW absorbers in turn at that point in time.

    Do that for enough times during the simulation period and hopefully you average out all the effects to come to some sort of useful set of figures for each LW absorber.

    Please correct me if I’m wrong and please reinstate my boreholed post. There seems little reason for it to be there.

  44. 144
    Edward Greisch says:

    Raymond Pierrehumbert: I love your page
    I read “A palette of climates for Gliese 581g” yesterday. Thanks much.

  45. 145
    TimTheToolMan says:

    ” If that was a misunderstanding, and you don’t want to be misunderstood, you ought to try being clearer about what you mean.”

    I see you’re about to release a paper on snowball earth. So for clarification and since if anyone knows its presumably you at this point, do we even have CO2 reconstructions back that far? Or is your paper entirely model based?

    Anyway this has gone way off topic and probably far enough for the moment.

  46. 146
    JBL says:

    @David B. Benson: Following you off topic a little, re: Perelman and Poincare — first, a little typo: it’s the Clay Research Foundation, not \Cray.\ Second, I think the main lesson to draw from this (aside from it being an interesting story) is that very brilliant people are also sometimes eccentric, and this seems to be true in Perelman’s case. In particular, his research didn’t rely on the internet in any meaningful way — in an earlier era, he would have mailed copies of his paper to the community to announce his result instead of posting it on the internet, whence it would have been distributed further, with exactly the same effect. (In fact, it’s important to note that the paper was not accepted as correct until it underwent a peer review process of a sort, just not one housed in a standard journal.)

  47. 147

    I’m back, for the moment. Thanks to Bob Sphaerica who was apparently the only one here who even noticed I had left.

    My paper for J. Clim. was turned down. Point to you, dhogaza.

  48. 148
    Hank Roberts says:

    TtTM asks if there are paleo records for the snowball earth period?
    TtTM can find this by clicking on the link posted previously, it’s here

    TtTM, one answer to your question is right there–on the front page.

    Further for TtTM: watch “… with inline responses” links — right hand side.

  49. 149
    JBL says:

    Addendum to David B. Benson: but, probably, you didn’t need me to tell you any of that :)

  50. 150
    Chris Dudley says:

    Phil (#121),

    Yes, I left out the rain part. I was distinguishing in my mind ocean carbon dioxide and atmospheric carbon dioxide. Thus the adjective.

    This is part of a somewhat esoteric discussion of a moist greenhouse where continental weathering slows or stops owing to lack of precipitation but ocean weathering picks up owing to faster reaction rates at higher ocean temperature (and presumably higher acidity rapierre?). Raypierre gave an AGU talk on this that I have not been able to find yet. My question is does not sedimentation put an end to ocean weathering?

    Perhaps it would help to look at this from the perspective of silica.

    In this figure from this paper:

    units are teramoles of silicon per year. As you can see, aeolian and riverine inputs dwarf ocean weathering inputs. As a rough mirror to the metal ion budget needed for the limestone sequestration thermostat, we would require ocean weathering to increase by a factor of 14 or so to keep up with volcanic inputs of carbon dioxide and more to mop up the oxidation of all available organic carbon (on the order of 30 teratonne of carbon )

    That the continents provide much more silica to this budget than the oceans despite the oceans covering more of the Earth’s surface is partly understandable in terms of the continents exposing much more fresh surface area to chemical weathering than the oceans. Much of the ocean floor is covered with sediment that is the end product of weathering. Currently silica becomes sediment through the sinking of diatoms but before these evolved, it precipitated out as an amorphous gel just in the regions where new surface is exposed to chemical weathering. Either way though, sediment or gel, the need to soak up much more carbon might well bury the very source rocks needed to provide metal ions in a precipitation constrained world regardless of accelerated reaction rates.

    In that case, the carbon dioxide content of the atmosphere would grow rather than get cleaned up and the loss of the oceans to space through a damp stratosphere would become inevitable (modulo raypierre’s worry about clingy oxygen though we know there is quite a bit of oxidizable manganese, nickle and copper in the deep oceans to give a little relief).

    Raypierre (#111),

    Since Hansen has provided a detailed argument in support of his claim, I’d like to dig into it and see how robust it is. If it turns out to be robust, my experience with how we persuaded Senator Mitchell to support nuclear arms control suggests a path to persuading current politicians about controlling carbon dioxide emissions. At that time, church groups (which devote a portion of their thinking to the end of things) became persuaded that support of the arms race would lead inevitably to nuclear war owing to eventual error in the handling of the weapons or use of the warning systems etc…. That made it urgent to turn things around as a moral issue. It did not matter much when the accidental start of a nuclear war might occur, only that it must occur with a continued arms race. When a Senator has to attend meeting after meeting after meeting with all the church groups in his state, it wears him down. It has actually been good for him since he has gone on to bring peace to Ireland and is working on the Mideast now.

    If Hansen’s claim of a dead certainty is correct, then the same kind of urgency applies. It is not a matter of weighing mitigation against adaptation, it is a matter of changing direction. That is something that moral people are called to do now, not later. Once persuaded, churches are capable of changing the sign of the derivative, not just its magnitude. We’ve seen that with abolition, civil rights and nuclear freeze.

    So, it is both a matter of curiosity to try to follow Hansen’s arguments though in detail because the claim seems extraordinary and matter of long vocation to bring about positive change and the experience associated with that effort.