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One year later

Filed under: — gavin @ 20 November 2010

I woke up on Tuesday, 17 Nov 2009 completely unaware of what was about to unfold. I tried to log in to RealClimate, but for some reason my login did not work. Neither did the admin login. I logged in to the back-end via ssh, only to be inexplicably logged out again. I did it again. No dice. I then called the hosting company and told them to take us offline until I could see what was going on. When I did get control back from the hacker (and hacker it was), there was a large uploaded file on our server, and a draft post ready to go announcing the theft of the CRU emails. And so it began.

From that Friday, and for about 3 weeks afterward, we were drafted into the biggest context setting exercise we’d ever been involved in. What was the story with Soon and Baliunas? What is the difference between tree ring density and tree ring width? What papers were being discussed in email X? What was Trenberth talking about? Or Wigley? Or Briffa or Jones? Who were any of this people anyway? The very specificity of the emails meant that it was hard for the broader scientific community to add informed comment, and so the burden on the people directly involved was high.

The posts we put up initially are still valid today – and the 1000’s of comment stand as testimony to the contemporary fervour of the conversation:

I think we did pretty well considering – no other site, nor set of scientists (not even at UEA) provided so much of the background to counter the inevitable misinterpretations that starting immediately spreading. While some commentators were predicting resignations, retractions and criminal charges, we noted that there had not been any scientific misconduct, and predicted that this is what the inquiries would find and that the science would not be affected. (Note, the most thorough inquiry, and one that will have to withstand judicial review, is the one by EPA which, strangely enough, has barely been discussed in the blogosphere).

Overall, reactions have seemed to follow predictable lines. The Yale Forum has some interesting discussions from scientists, and there are a couple of good overviews available. Inevitably perhaps, the emails have been used to support and reinforce all sorts of existing narratives – right across the spectrum (from ‘GW hoaxers’ to Mike Hulme to UCS to open source advocates).

Things have clearly calmed down over the last year (despite a bit of a media meltdown in February), but as we predicted, no inquiries found anyone guilty of misconduct, no science was changed and no papers retracted. In the meantime we’ve had one of the hottest years on record, scientists continue to do science, and politicians…. well, they continue to do what politicians do.

442 Responses to “One year later”

  1. 401
    Rod B says:

    Ray,are you saying the inputs for the different climate models are INDEPENDENT (your emphasis)? Like in near random variance? Other than detail variations around the edges of this or that parameter of this or that algorithm, the inputs are pretty much the same for all models. Unless the system programmer screwed things up badly, the output from all of the models are going to look very close. That by itself does not indisputably prove much.

    I don’t think (and never said or implied) the models are “entirely wrong.” I think they are mostly right (‘mostly’ here is way more than 50%), quite good, and useful. But certainly not irrefutably perfect or God-given as Barton (and others…) would have us believe. Nor are the inputs pure physics, as opposed to a pile of short cuts, generalized assumptions, and estimates or guesses (which might be very logical…) made by human scientists to fill in those areas where the physics is just a bit deficient or unknown.

  2. 402
    Anonymous Coward says:

    Sensitivity has been likened to the gravitational constant in this very thread:
    “I find it astounding that you can look at all the evidence constraining climate sensitivity and call the fact that sensitivities in models reflect this an “assumption”. Is the value of the gravitational constant an assumption as well? How about the value of the electron’s charge?”
    I agree sensitivity isn’t an assumption and I don’t think the commenter who wrote that is confused but that wasn’t just a poor analogy. Here’s another quote, from that knowledgable commenter:
    “Based on evidence, the 90% CL for climate sensitivity is 2.1 to 4.5 degrees C per doubling. This means there is only a 5% chance that the evidence to date could be so skewed that the actual value could be outside this range.”
    Again, I don’t disagree with the sentiment but the wording could well confuse less knowledgable readers. Instead of your “range of probability” which I think is a good way to put it, the quote refers “actual value”, again as if it was a property of the physical system, as if we would finally know the “actual value” the day the good people at Mauna Loa get a 550 pmm reading on atmospheric CO2 or something.

    I would rather not name the names of some well-meaning commenters who seem to be truely confused. I would have to mine other threads which I don’t want to do either. But I’ll give you a hint: they tend to be more alarmed than most by the “target atmospheric CO2” paper and other writings of Hansen.

  3. 403
    Sir says:

    396 Coward
    I checked out the Wiki article you linked. It referred to the astrophysical expectation that the Sun’s output would be only 70% as intense 4 billion years ago. First, this was an expectation and it is inconsistent with the fact that there was liquid water at the time. Second, it was 4 billion years ago. This evidence gives no support to Alan Millar’s firm statement that the Sun has and will continue to increase its output and therefore the radiative forcing effect on the Earth. Until there is a good citation for this speculation, he is making it up. In addition, as has been pointed out before, there is a difference between the sun’s output and the radiative forcing effect on the Earth due to the Milankovitch cycles. Finally, there is little relevance to the sun 500 million years ago to what will happen in the next few hundred years.

    [Response: While it is true that the 500 million year time scale is not the most direct way to look at what is going to happen in the next hundred years, it isn’t fair to dump all of that information as being ‘made up’. The sun is a main sequence star and astrophysicists have a pretty good idea of their evolution from studying all the differently aged stars we can see. A main sequence star does become brighter over the billion-year time periods as it uses up it’s hydrogen and makes helium. It will eventually use up all the hydrogen and become a red giant (some 5 billion years from now), and which point any planet-bound descendants are toast. Trying to work out why the Earth was not a Snowball for earlier periods is an interesting field of study (involving greenhouse gases, continental configurations, aerosols, atmospheric chemistry, evolution etc.), but the mere fact of uncertainty in this does not support either Millar’s point nor yours. – gavin]

  4. 404

    #402 Anonymous Coward

    I believe you are mistaken. It is not a comparison, it seems more analogous.

    The point is that there is good and useful knowledge in these areas.

    You can try to spin it to your purpose as you desire, but spin is still just spin.

  5. 405
    Hank Roberts says:

    AC, climate sensitivity _for_conditions_now_ is understood pretty well by most commenters here (and by Hansen and by the hosts at RC).

    None of them think climate sensitivity is a universal constant like gravity or electron charge — but it’s something that can be figured out and that’s
    analogous if you ignore the fact that deep time is awfully deep.

    Climate sensitivity will come out different when the details like the state of the ocean circulation, the exposed rock and weathering rates, and what lives in the oceans changes. No question. Evolution of plankton changed climate sensitivity hugely.

    That doesn’t matter now, unless ocean plankton changes drastically with the current unprecedented rate of ocean pH change from adding CO2. Ooooops.
    Gravity is not susceptible to human meddling, as far as we know.

  6. 406
    Ray Ladbury says:

    Anonymous Coward,
    The value for CO2 sensitivity at any given time is in fact a single value, with actual probability function a delta function at that value. The probability distribution with 90% CL from 2.1 to 4.5 K/doubling and favored value of 3 is in fact a subjective probability that reflects the state of our knowledge.

    Also, my reference to the value of G or electron’s charge was meant to emphasize that these values too are empirically determined by analyzing large amounts of data. It is identical to the case for CO2 sensitivity being independently constrained by data.

  7. 407
    Sir says:

    Point well taken. I was pilling on. However, my main point to Millar is that contrary to his assertion that there must have only been negative feedback while the sun was warming, there have been both positive and negative feedbacks in response to the sun increasing and decreasing its radiative impact on the earth caused primarily by the Milankovitch cycles over the last 400,000 years.

  8. 408
    Anonymous Coward says:

    “Conditions” may become significantly different than today’s even before breaking 550ppm. I don’t know that we have a good handle on the potential implications. Going by the uncertainty regarding the impact of Groenland and Antarctica on SLR, we seem to be pretty much in the dark with regard to the timeline especially.
    What I’d like to know is the timeframe in which the assumptions underpinning the consensual sensitivity range are likely to remain valid and what might be the impact of future emissions on that timeframe.

    The value of the gravitational constant can be determined experimentally. The validity of such a determination can be tested.
    What does it mean to say that sensitivity is an “actual value”? It would seem to imply there is an objective value that can be discovered somehow as opposed to “a subjective probability that reflects the state of our knowledge”.
    When you write “at any given time”, do you mean to say that sensitivity has a meaning separate from the time required for the system to come into equilibrium?

  9. 409
    Hank Roberts says:

    AC — nonsense; read James Annan’s work for example.
    ‘charney sensitivity’ — the difference between short and long term.

    How could the physical condition of the planet changed enough to “significantly” change the sensitivity in decades? — we’d be toast.

    Or of course we’d have been saved by a miracle if it were in the other direction. Won’t happen. Not physically credible.

    What could happen? We won’t open the Isthmus of Panama, or build a mountain range, or double the amount of photosynthesizing plankton (though we could cut it in half, credibly enough).

    You’re making this up. It’s nonsense. You’re just saying “something could happen to make it not so.”

  10. 410
    Hank Roberts says:

    Ray, don’t take it to the extreme that lets it be easily mocked.

    Yes, “CO2 sensitivity at any given time is in fact a single value”
    but remember — it’s determined AFTER the fact.

    It’s the temperature difference when radiative equilibrium is attained again after a change in the forcing.

    Whether you get a big methane burp or not changes the result.
    That’s one source of the uncertainty. Time will tell.

    Whether you get a big change in ocean plankton changes the result.
    That’s another source of the uncertainty. Time will tell.

    We know a lot of the forcings within reasonable limits.
    We know a lot of the feedbacks.
    We don’t know for sure which feedbacks will go how far.

    Worst case in the past — PETM.
    But that excursion started from a very different world than this one.

    Do we expect to cause another PETM excursion?
    We hope not. We don’t know if we will.

    So yes, climate sensitivity is a distinct, single number.
    It is going to be computed by the Earth, in real time.
    The number will be determined after the fact.

    Actual scientists should correct the above.
    It is at best doggerel.

  11. 411
    Hank Roberts says:

    What you also need to remember — in real time, in real life, climate sensitivity is not for a 2x change in greenhouse gases. Climate sensitivity is the actual change in temperature after a single pulse of extra forcing, whatever it is — that starts the planet’s temperature rising by delaying release of heat to space; the temperature of the planet rises until radiative equilibrium (heat going out at the top of the atmosphere) once again matches incoming energy. Ding, take the number please, calculate change in temperature for observed change in greenhouse gas. That’s the sensitivity.

    Then there’s a long, long, slow, slow decline in both greenhouse gases and temperature as biogeochemical cycles, the long slow ones, remove the greenhouse gases from the atmosphere, then do something with them that puts the carbon back into longterm sequestration.

    So during that time you could calculate the sensitivity for a given _decline_ in greenhouse gases.

    CO2 as Alley reminds us is the one big control knob on this process.

  12. 412
    Ray Ladbury says:

    OK, I can see that my comment about subjective probability was not understood. Let’s try again.

    What I meant was that for a given climate at a given time, CO2 sensitivity cannot assume any value in the range 2-4.5 K/doubling. It is in fact only one value, with the real probability distribution represented by a delta function at that value. The broad quasi-lognormal-shaped distribution we are familiar represents our knowledge of the sensitivity. And just a G is measured, climate sensitivity is also measured. It has uncertainties, but so does our determination of G. What matters is how well we know those uncertainties, and given the fact that we have so many independent lines of evidence that pretty much agree on the range of possible values, we know climate sensitivity quite well.

  13. 413
    Hank Roberts says:

    > like to know … the timeframe in which the assumptions
    > underpinning the consensual sensitivity range are likely
    > to remain valid and what might be the impact of future
    > emissions on that timeframe.

    Fair question, one for a real scientist. But it’s been
    asked and answered. Good place to begin:

  14. 414

    #385, Alan Millar–

    “Are you talking about the solar energy the Earth receives and re-radiates?”

    Yes, that is precisely what I am talking about. “Radiative forcing” includes the specifics of how Earth re-radiates or otherwise disposes of the solar energy coming in.

    (To be just a bit less terse, I’m throwing in the “otherwise disposes of” to allot a heading for things such as albedo effects, which may involve bypassing absorption in the first place, and so not technically come under the category of “reradiation.” Such things as land use changes or aerosol concentrations can nevertheless be associated with an equivalent value termed “radiative forcing.” See Gavin’s list–or the Summary For Policymakers, which tabulates this, IIRC.)

  15. 415
    Anonymous Coward says:

    You wrote “AC, I think you’re making that up. I’ve don’t recall any commenter here appearing to believe that ‘climate sensitivity’ is a physical constant.”
    How else do you interpret Ray’s #412?

    Yet I’m supposed to be making up something else. What exactly I can’t tell.
    I’ve read the report of the Charney committee but I can’t make sense of your quip: “‘charney sensitivity’ — the difference between short and long term.”
    The thing is, the actual slow processes do not wait until the faster processes reach equilibrium before having an effect. I don’t know how much overlap there is and, as I stated earlier, going by the lack of reliable SLR forecasts, it seems I’m not the only one in the dark.
    You ask “what could happen?”. As I hinted at, if enough ice melts on Groenland and Antarctica, it will have an effect on albedo and possibly oceanic currents. Something else which should be obvious is that vegetation affects albedo. And it seems there may be widespread severe droughts in a warming world. I guess there are other, less intuitive processes which also change the fixed conditions assumed by models.
    You link to a James Annan blog post but I don’t understand what it’s got to do with the issue at hand.
    The best data that could constrain sensitivity applies to climates colder to slightly hotter than the current one (at best). The post-doubling climate is a bit of an unknown territory.

    You say “climate sensitivity is a distinct number” that “is going to be computed by the Earth”. Is that some kind of thought experiment (akin to Laplace’s daemon) or do you (or Ray) think that number could conceivably be observed in practice in spite of the Earth’s rergettable tendency to change confounding variables on overlapping time scales.
    I guess you’re assuming that sensitivity would remain constant over the time necessary to reach equilibrium but that’s not sufficient. You’d also need it to remain constant between “experiments” (as with the gravitational constant) to show that the number which was measured is not a random point in a distribution but fixed value.
    Is there any physical reason to believe climate sensitivity is a single number as opposed to a range of probabilites to being with? There seem to be random unforced variations and I would therefore also expect forced variations to be somewhat random. Clearly the randomness is contrained but that doesn’t imply that there is an “actual value” underpinning the contraints.

  16. 416
    Hank Roberts says:

    I think Ray understands that climate sensitivity is an estimate, until the final number is in; your “… remain constant over the time” is a misunderstanding; there’s no abstract “climate sensitivity” that one can hope to influence or adjust or change, no dial.

    Sensitivity is the _end_result_ of a given pulse — a fixed amount added to the system — of CO2 or other forcing — in a given world.

  17. 417
  18. 418
  19. 419
    Anonymous Coward says:

    I’m not saying sensitivity can somehow be adjusted (now that would be neat!). It would however be possible to affect the temperature at which radiative equilibrium happens after a pulse by the way.
    I’m saying there’s no “final number”. Perhaps this is somewhat of a moot point since I don’t see how this “final number” could be pinned down precisely if it existed.

    The “end result” of a given pulse is arbitrary, not only because definitions of sensitivity are arbitrary but also because radiative equilibrium is transient, subject to seemingly (partially) random processes and slowly changing “conditions”. You’d have to be able to correct for all the other stuff that’s happening in the system to know exactly when the effect of your pulse is fully realized.

  20. 420
    Ray Ladbury says:

    No, climate sensitivity is not arbitrary. Ultimately it is determined by the temperature required to return to equilibrium–that is, the power under the new emission-spectrum curve equal to incoming power. For any particular beginning point of the climate, that is pretty well deterministic. What is “an estimate” is our knowledge of it.

    What is confusing is the fact that there are some “estimates” that use slightly different definitions of sensitivity–e.g. the Charney sensitivity, which does not include every possible feedback. The Charney estimate is probably a slight underestimate of the actual climate sensitivity.

  21. 421
    Hank Roberts says:

    AC, that’s what they do. See the papers and Annan’s blogging for how it’s done. There’s a “final number” from each period in the past that’s been studied, within the limits of the work done. You’re not still arguing about the “force of gravity/electron charge” notion are you? The people who put that analogy forward weren’t claiming a physical constant like the speed of light, and you must realize that by now. It’s well beaten horseburger.

    Repeating of blog philosophy won’t get you past the old exchange

    Emil du Bois-Reymond: “Ignoramus, ignorabimus”
    David Hilbert: “Wir müssen wissen — wir werden wissen!”

    “We don’t know, we can’t know” versus “We must know — we will know!”

    We do know within a confidence range sufficient to know we do have a concern, an immediate problem we began causing decades ago, overdue for intelligently designed response. And it’s up to us, it won’t be done for us.

    That’s what the science conversations are about. If you want to say the science can’t be done, standing in the way of people doing it just wastes everyone’s time.

  22. 422
    SecularAnimist says:

    Re: climate sensitivity.

    My sense as a non-scientist following this issue, is that the biggest uncertainty and the source of the potentially nastiest abrupt problems, is the ecological effects, as opposed to the relatively “mechanical” effects that I understand climate models to represent.

    Some of which ecological effects we are already seeing (corals, phytoplankton, pine bark beetle, etc), and which I would like to see discussed by relevant experts here more often.

    I think it more likely than not that a plausible AGW “Pearl Harbor” moment might not come as something like the sudden catastrophic collapse of a huge chunk of Greenland or Antarctic ice, but the sudden catastrophic collapse of a major ecosystem.

  23. 423
    Jeffrey Davis says:

    re: 419

    “to know exactly”

    People squeeze words like “exactly” and “uncertainty” awfully hard.

    No practical action depends upon exactness and certainty.

  24. 424
    flxible says:

    I think it more likely than not that a plausible AGW “Pearl Harbor” moment might not come as something like the sudden catastrophic collapse of a huge chunk of Greenland or Antarctic ice, but the sudden catastrophic collapse of a major ecosystem.

    Watching the politics, it seems much more likely humanity will end with a whimper than with a bang.

    CAPTCA agrees: circle forthill ;)

  25. 425
    Anonymous Coward says:

    Blog sophistry notwithstanding, there are fundamental disagreements here.
    Ray claims sensitivity is “pretty well deterministic” while the underlying system is not (so far as I know, that’s not controversial outside of RC comment threads). Ray’s claim is counter-intuitive but, if you’ve got references showing that the non-deterministic aspects of the system don’t affect the response to forcings or simply quantifying Ray’s “pretty well”, I’d appreciate them.
    You apparently believe, unlike Ray, that sensitivity is not deterministic (you stated it could only be known after the fact) but could nevertheless be measured precisely. And I figure (I’m not particularly confident in my reasoning here) that precise measurements can not be done because there are non-deterministic confounding processes.

    I’m not standing in the way of people doing science (how would I do that?). Please give the paranoia a rest. And I’m not saying any of this is relevant to mitigation policies either.
    I’m looking at well-known physics (the lower the albedo, the stronger the H2O feedback for instance) which implies that, even if there were no discontinuities (see #422), sensitivity should change on the timescale needed for the oceanic temperatures to respond to a forcing. That in no way implies that sensitivity can’t be constrained or something.

  26. 426
    Hank Roberts says:

    > sudden catastrophic collapse of a major ecosystem.

    Almost nobody noticed when that happened.

  27. 427
    Ray Ladbury says:

    AC: “I guess you’re assuming that sensitivity would remain constant over the time necessary to reach equilibrium but that’s not sufficient. You’d also need it to remain constant between “experiments” (as with the gravitational constant) to show that the number which was measured is not a random point in a distribution but fixed value.”

    AC, this simply is not true. If it were, then biology, meteorology, geophysics, Solar physics… would all be impossible. What matters is understanding what the changes can be and whether they are important. Fortunately, in the case of climate sensitivity, many of the important feedbacks are not highly variable on decadal timescales. And the advantage of the Charney sensitivity is that it includes the feedbacks that tend to be relevant to those timescales. It does no good to throw up one’s hands at complexity–better to roll up one’s sleeves.

  28. 428
    Hank Roberts says:


    This is an example of paleo work determining a climate’s sensitivity to CO2 change. Note it’s _a_ climate’s sensitivity, that particular climate including the geology over the time.

    Rate of change matters; doubling CO2 in 200 years will overwhelm some feedbacks that were working when nature doubled CO2 in 400,000 years.

    If aliens were causing this change, Earth would unite to stop the attack.

  29. 429
    Anonymous Coward says:

    I’m not aware that “biology, meteorology, geophysics, Solar physics…” require assuming that arbitrary properties of non-deterministic systems can be reduced to fixed values. Nor does climatology of course.

  30. 430
    Bill says:

    Hank, as people who follow the science will understand, this is true. But, what do the scientists on here want done about it ? What needs to be done over what timescale? Its no good keep repeating the science which most people on here have already heard and well

  31. 431
    Ray Ladbury says:

    AC, don’t confuse weather with climate. Weather is not deterministic. Climate responds to small changes in a predictable fashion. And THAT is not controversial. And oceans equilibrate (at least in the first few hundred meters) on decadal timescales. Is it seriously your contention that climate sensitivity is significantly different (e.g. outside the 90% CL) since 1980? What in your opinion has changed in that time to such an extent.

    Does it mean nothing to you that all the diverse lines of evidence wind up pointing to a sensitivity in the same range? Surely that ought to give you something to think about?

  32. 432
    Anonymous Coward says:

    The difference between weather and climate is arbitrary. That doesn’t mean the distinction is unfounded, just that the exact same processes drive both and that there is no physical boundary between the two. It seems there usually are negative feedbacks on unforced variations so that one would expect the unforced variations to be less between 30 years periods than between years. But less doesn’t amount to zero.
    There’s for instance the 1940-1975 (or something like that) period. It’s long enough to be climate by the standard definition but how can you explain it if you assume the climate to respond in a deterministic fashion to “small changes” (not sure what you meant there, quantatively)?
    Th extent to which climate is predictable is somewhat controversial… or at least it was a few years ago when credible scientists were discussing the issue on RC. There are people who would try to use that relative unpredicability as fodder in their crusade against reason but denying the unpredictability in the hope of taking away one of their arguments is just as irrational.

    Going by the IPCC models, the oceans “equilibrate” over centuries and surface temperatures would be expected to climb slowly as a result (see AR4). If you take that away from your definition of sensitivity, I guess it should be possible to narrow the range of plausible values.

    So far as I know, there’s no indication (albedo for instance) that there has been a major change in sensitivity since 1980. But I can’t rule it out.
    Recall that Hansen has apparently seriously contended that a runaway H2O greenhouse would be probable if unconventional fossil fuels were fully exploited. So sensitivity would at some point change from some range around 3C to more than 500C per doubling! I don’t give that contention much weight but I don’t know that less dramatic discontinuities can be ruled out such as the ones which might lurk in the paleo record (PETM for instance if the hypothesized temperature spike isn’t fully explained by methane or some other external forcing).
    If one was to use Hank’s definition according to which sensitivity is a variable property of the physical system which can only be determined after equilibrium is reached, if follows that we can not know if there was a recent discontinuity in sensitivity. A discontinuity in the physical system 100 years from now would retroactively change sensitivity up to the point at which CO2 concentration was half its pre-discontinuity value. I do not care for such games (spooky effect from the future!) so I would prefer to define sensitivity as a range of probabilities reflecting our understanding of the physical system.

    What the lines of evidence tell me is that, as I stated earlier, the “actual” sensitivity range is likely within the range the evidence is pointing to. Duh. While the “actual” range would likely be smaller, it does not follow that it would be small enough that reducing it to a single value would be a good approximation.

  33. 433
    Hank Roberts says:

    > Hank’s definition

    -my- definition? Nonsense. I looked that up; it’s not mine.

    > 1940-1975?

    Perhaps you missed all the prior discussion because it’s usually called 1940-1970. Try“1940-1970”

    (the double quotes may get mangled, but you know what to do)

  34. 434
    Ray Ladbury says:

    AC says, “The difference between weather and climate is arbitrary.”

    OK, now you are just being silly. I’m sure Gavin would be shocked to find the he was just a meteorologist. Dude, I suppose you consider day trading, playing the lottery or betting on the ponies to be equivalent to serious investing, too.

    AC, we have something in common. Neither of us has a fricking clue what you are talking about.

  35. 435
    David Miller says:

    AC, I’m not following you at all in #432. I’m not sure if you’re babbling, trolling, like to hear yourself talk, or are just confused.

    When, for example, you say something like:

    Recall that Hansen has apparently seriously contended that a runaway H2O greenhouse would be probable if unconventional fossil fuels were fully exploited. So sensitivity would at some point change from some range around 3C to more than 500C per doubling!

    you’re not making sense at all.

    Hansen suggested that a runaway greenhouse effect could start from as little as around 20 w/m^2 (that’s from memory, don’t quote me on it). How you get from 20 w/m^2 to 500C per doubling is a big mystery to me.

    What you seem particularly confused about is whether ‘climate sensitivity’ is a constant or not. Let me attempt to clear up some of the confused talk that’s been going on about that…

    First, as I understand it, ‘climate sensitivity’ is not a physical constant like the charge on an electron. It’s generally regarded as how much the Earth warms, on average, for a doubling of CO2e.

    When you start looking very closely at that number you have to start asking ‘over what time frame’, because different parts of the environment warm at different rates. Land first, deep ocean last. Everything else somewhere in between.

    Second, no one around here will treat it as a simple constant simply because of the Earth system feedbacks. There’s the simple water vapor issue that turns the 1.2 degrees per doubling of just CO2 into something closer to the 3 degree estimate, but that’s pretty much instantaneous. As other parts of the environment warm other feedbacks kick in. For example: Warmer winters mean pine bark beetles don’t die off, forests die because of the beetle, lightning starts fires, and carbon sequestered in forests goes back to the atmosphere. Permafrost melts and carbon stored for millenia is turned into methane. Warmer soils break down organic matter faster. There’s a long list of things that add CO2e to the air as the climate warms.

    What this means, AC, is that we can’t determine an exact value for climate sensitivity after the fact because we can’t hold CO2e levels steady for a century or more to determine what it would be. It’s a moving target.

    Lastly, as Ray often points out, we don’t really need an exact number to decide whether we should do something about it or not. 2C would be extremely bad because of the other feedbacks – a few of which I mentioned. And it would also be extremely fortunate if sensitivity were really that low – the data is centered around something very close to 3 degrees, not 2. We need to start about 20 years ago if we want to do something about it before we run into real problems.

  36. 436
    Hank Roberts says:

    > doubling … 500 degrees C
    Hilarious. And the temperature on Venus proves what to you? Never mind. We know you’re having us on. The references are for anyone coming along later:

  37. 437
    Anonymous Coward says:

    I don’t know how Hansen’s runaway works obviously (does anyone?) so I assumed it works like the standard theoretical runaway. I didn’t go from W/m^2 to C. I went from the mass of the oceans to a temperature since that’s what determines the temperature after a runaway. What makes a runaway is that the feedback from the condensating GHG becomes effectively infinite. Hence the grotesque sensitivity. It’s not spread out over the 20W/m2 (or whatever) because sensitivity accelerates fairly brutally as you get close to the runaway point. Still, I agree >500C per doubling might have been excessive… perhaps 450C for the final doubling would be more like it. Not that the exact number matters.

    As to the rest of your comment, I have no issues with it other than the “no one around here” bit so I must be confused about something else.
    I was saying (among other things) that, even if you could hold CO2e levels steady for 1000 years, you couldn’t determine an exact value for sensitivity by observing the response of the physical system.

  38. 438
    Snapple says:

    CM writes:

    “Assange is talking nonsense. The stolen emails were hacked into this site’s server first, and were downloadable from Tomsk for the first days of the affair. Had Wikileaks sprung them, Wikileaks would have published them on their own site first. I’m not sure which is the most distasteful, fencing stolen private correspondence to the world, or falsely claiming credit for it so you can frame yourself as the victim of a British secret service disinformation plot. But I’m pretty sure which is the most ridiculous.”

    I don’t think this is right.

    I saw a link to those files on a blog comment a few days before it was on Real Climate.

    I didn’t understand what I saw except in retrospect, and the blog comment was removed shortly after. The file introduction did make it clear it was something stolen that was personal correspondance. I didn’t look at too much after I realized that. I didn’t like that someone put private e-mail on the Internet and boasted about it.

    I am pretty sure this file was already making the rounds on blogs on about November 14. Real Climate was hacked on Nov. 17, I think.

    As for the British secret service linking Assange to the FSB, I wrote that I thought Climategate might be some Russian operation a week before the British papers or the UN talked about the possibility of a Russian role.

    I’m nothing to do with the British secret service, and I never knew about Wikileaks.

    I just think Climategate was just like Russian kompromat, and I noticed the Russian press was very quick on the Climategate story. That’s what they do to people in Russia all the time–they publish some embarrassing, compromising secret.

    One year later, we still don’t know who stole the e-mails, who spread them on the Internet, and who put them on Real Climate and the Tomsk server.

    The files were also on some other servers.

    I hope the authorities know more.

    Wikileaks does have information about how the Russians are bribing politicians with their oil money. That’s not exactly news. Maybe people read it because it’s a “secret,” but lots has been published about how the Russians are corrupting politicians.

    What the authorities know about that is a lot more than what appears in State Department cables. That would only be the tip of the iceberg.

  39. 439
    Ray Ladbury says:

    AC, you are talking nonsense. You need to go back and look at how feedback works in climate science. You seem to have this idea that climate is metastable and balanced on a knife edge. ‘Taint so.

    Gavin, perhaps another tutorial on feedbacks, sensitivity, etc. Since climate depends on AVERAGE behavior, it is actually behaves fairly consistently for small changes in forcing. Go back and look at the barious sensitivity studies and ponder what it means that they all yield about the same favored value for forcing and consistent confidence intervals.

  40. 440
    Hank Roberts says:

    Shorter AC: ignoramus ignorabimus
    ‘Shorter’ concept created by Daniel Davies and perfected by Elton Beard. We are aware of all Internet traditions.

  41. 441
    NoPreview NoName says:

    @Hank Roberts, #411

    That Alley lecture was really good. I particularly liked the graph showing that high cosmic ray flux had no observable affect on climate.

  42. 442
    David Miller says:

    AC says in #437:

    I was saying (among other things) that, even if you could hold CO2e levels steady for 1000 years, you couldn’t determine an exact value for sensitivity by observing the response of the physical system.

    That’s just wrong. If you could hold the CO2e level steady, somehow, for 1000 years you’d get the value of the millenial response.

    The rest of your post is still nonsense. I have no idea where you’re coming up with a sensitivity 100x what anyone else has ever mentioned.

    I’d strongly suggest that before you post more things like I don’t know how Hansen’s runaway works obviously (does anyone?) so I assumed …. that you find out how Hansen’s runaway was posited to work.

    You might also read a little on the current state of climate research before thinking you know how a standard theoretical runaway works. Go to the realclimate home page, click on ‘start here’ and read for a good long while.