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A Scientific Guide to the 'Skeptics Handbook'

Posted on 1 July 2010 by John Cook

Not long ago, I read the Skeptics Handbook which displays some fundamental misunderstandings of how our climate works. I wondered whether a rebuttal of this document would be worthwhile but when I floated the idea to a few people, the general response was "been there, done that". It turns out there are a number of detailed rebuttals of the 'Skeptics Handbook'. Desmogblog wrote a 3 part series in 2008 (parts 1, 2 and 3). has a useful set of short rebuttals with links to longer answers. Tim Lambert also examined some of the arguments. So the 'Skeptics Handbook' had been rebutted on multiple occasions.

Nevertheless, there was something else that needed to be said. The 'Skeptics Handbook' begins by asking "what evidence is there that more CO2 forces temperatures up further?" It then lays out 4 arguments: the greenhouse signature is missing, CO2 lags temperature, it's not warming and the CO2 effect is saturated. The great irony of the 'Skeptics Handbook' is when you examine these 4 arguments and the full body of empirical evidence that goes with them, what you actually find is the evidence that more CO2 forces temperatures up further. Here's a brief description of how the Scientific Guide examines 4 human fingerprints on climate change:

  1. As greenhouse gases stop heat from reaching the upper atmosphere, a distinct greenhouse signature is a warming lower atmosphere and cooling upper atmosphere. This is exactly what's observed by satellites and weather balloons.
  2. Satellites measure more heat being trapped by CO2. On top of this, ice cores find temperature affects the amount of CO2 in the air. So warming causes more CO2 and more CO2 causes warming. Put these two together and you get positive feedback.
  3. The surface temperature record shows that the number of warm nights are increasing faster than warm days. This is another effect of greenhouse warming.
  4. To find out whether the CO2 effect is saturated, we just have to look at direct measurements - satellites find CO2 is trapping more heat and surface measurements find more heat returning back to Earth.

All 4 arguments highlight 4 distinct human fingerprints on climate change. Once I'd compiled all the evidence into a single document, I sent it around to a handful of climate boffins to nitpick any inaccuracies in the text. Much thanks must go to the scientists who examined the Scientific Guide and helped clarify the text (they're all acknowledged in the inside cover). Much proofreading credit must also go to my wife Wendy who offered a crucial layman (laywoman?) perspective. Scientists tend to take technical language for granted and she was instrumental in boiling down much of the jargon into plain English. She also created the design which I think has a pretty awesome look.

You can download A Scientific Guide to the 'Skeptics Handbook' as an A5 PDF. The booklet is actually designed to be printed out on A4 then folded to A5. So if you want to print out the booklet, here's the A4 imposed version. I hope you all enjoy the Scientific Guide and feedback is welcome.


Many thanks to all those who generously donated their time to translate the Scientific Guide into other languages.









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Comments 51 to 73 out of 73:

  1. johnd > According to what you have stated, if I get a block of ice from the freezer and put it in the room, the ice will emit extra thermal radiation into the room in all directions because it can't sense any incoming radiation. Yes. Remember that every singe molecule in the room is emitting radiation, including your own molecules and the walls surrounding you. What's really important in your scenario then is the radiation of the ice block relative to what is behind it (from your perspective). If it blocks something emitting less radiation than itself, then it adds to how much thermal radiation you are absorbing, no matter the distance. If it blocks something emitting more radiation, it reduces the radiation reaching you no matter the distance. In the first case of course conduction eventually cools you. In both cases in net the ice block receives more radiation from you then you receive from it, so in net energy is moving from the hotter object to the cooler. The difference is that in the first case the rate that energy moves from you to your surroundings is reduced very slightly, in the second case it increases very slightly. The greenhouse effect works to reduce the rate that energy moves from the warm surface up to the cold stratosphere and out to even colder space. Again that is a critical point so make sure you understand it: Energy is still flowing from warm to cold; it's just slowed down. Anyways, it is a physical fact that all objects warmer than absolute zero emit thermal radiation in all directions, irrespective of their surroundings. This is basic physics JohnD, you do your credibility no favors by trying to argue against it (if indeed that is what you are arguing).
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  2. Congratulations, a splendid effort at producing a booklet which sets out in clear, easily understood language what we know about the causes and some of the consequences of Global Warming – or to be more accurate AGW? It is so good that I am surprised not to see the authors name on the present draft. Why? I make a few suggestions and comments below which might (?) improve the content without making it too long. Page 1. Humans are emitting billions of tonnes of CO2 into the air every year. Very true but surely the most important point is that they are doing so by burning fossil fuels rather than fuels from currently living or recently dead sources. The result is of course not only the addition of CO2 into the atmosphere but (a) CO2 which without human activity would never have entered the atmosphere (hence AGW) and (b) the speed with which this is occurring is unprecedented – as is the speed of its consequences. Page 4. So warming causes more CO2 and more CO2 causes warming. But surely it is the other way around because of the high and increasing level of CO2 emitted by humans – More CO2 causes warming and warming causes more CO2, for example as a result of warming seawater giving up CO2, warming tundra giving up CH4, etc. Page 7. Ice sheets are melting loosing billions of tonnes of ice each year. True but would it not be more accurate to say: Land based ice is melting and doing so at an increasing rate, loosing billions of tonnes each year (as shown by Grace satellite measurements) Admittedly the WAIS is a marine ice sheet rather than land based but some parts of it are on land. Page 7. Sea levels are rising at an accelerating rate I largely due to diminished ice sheets). Also true but a very significant cause is also thermal expansion of seawater. Is that worth mentioning? Might the effects of rising sea levels get a mention – specifically the threat to erosion of coastlines, salination of fresh water sources and of course the loss of public infrastructure, housing and industry, as pointed out in the House of Representatives Standing Committee on Climate Change Report on Climate Change Impacts on Coastal Communities ( Page 7. Glaciers are retreating, threatening water supplies for millions of people. Might one add: their livestock and agriculture? And if it were only “millions” maybe we should worry less but the threat is probably far greater – affecting hundreds of millions if not billions of people. Again this is confirmed by Grace. Page 7. Might an additional dot be added to draw attention to the albido feedback effect ( which is contributing to both the accelerating rate of temperature increase and ocean warming in polar regions, and retreat of glaciers. Page 9. Map showing Trend in downward infrared radiation. As far as I am concerned it is quite clear and understood. But how about guys and girls who are unfamiliar with this kind of representation? Might a bit more explanation be given of what this ma is telling us? Might it be appropriate to mention in this book the effects of continued increasing CO2 emissions, which of course include the following: • melting of the polar ice caps • dangerous sea level rise and coastal flooding • melting of land based snow and ice, contributing to • shortage of water in densely populated areas • extinction of flora and fauna dependent on cooler climates • increased risk of fire destroying valuable assets • loss of capacity to produce food for rapidly growing populations • increased incidence and severity of climate events • increased water vapor in the stratosphere causing further warming • spread of potentially fatal diseases into areas now free of them • ocean acidification damaging the marine habitat and • threatening a break in the food chain for fish on which humans depend.
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    Response: Thanks for the suggestions. To address some of your comments and questions:
    1. The author's name (John Cook, aka me) is on the inside front cover, the 2nd page of the document
    2. Page 1: Good points re the speed of the CO2 emissions being unprecedented but there is only so much space so I went with the most fundamental point - we're emitting CO2 (and lots of it)
    3. Page 4: the central point I wanted to make here was that the CO2 lag doesn't disprove CO2 warming. In essence, it does the opposite of what the skeptic argument is getting at, it actually provides evidence for positive feedback. I decided to go with just this simple point - although mentioning the permafrost, warmer seawater is a nice idea.
    4. Page 7: I frequently mention the accelerating ice loss on the website but that page has very limited space as I'm listing a number of different signs of warming. Ice sheets by nature are land based while ice shelfs are floating on the water.
    5. Page 9: I might have to scratch around for a different depiction of increasing downward infrared radiation. I also found it clear and vivid (and colourful, that was a big factor!) but perhaps a simpler, more intuitive graph would be better. Thinking about this.
    6. Re other effects of continued CO2 emissions, again, a good list but there just wasn't the space. Of course I could've just added more pages but I think when you're communicating science to a broad audience, you have to be quite harsh in what you cut out otherwise you risk swamping the reader with too much information. This then dillutes your central message. So I chose to emphasise one central message - there's a human fingerprint on climate change then look at the evidence for the fingerprint.
  3. Dr. Pielke is very annoyed to the point of publicly expressing dubious speculations about the honesty of NSF officers because a project of his own to investigate anthropogenic climate change factors was turned down for funding by NSF, unfairly according to Pielke. He's been making quite a stir about the matter so it's no surprise he should turn up on RealClimate promoting alternative anthropogenic climate change attributions. He's waging some kind of campaign, judging by his own words at his blog.
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  4. As the Earth's atmosphere is composed of mainly N2 and O2, it would seem important to know how these gases are known to cool. Is this explained in the book? When you are always hearing about water vapor and CO2 absorbing IR, one is led to assume that the other gases (by contrast) must not do so. Also, for IR transmission, it doesnt seem like this could happen in a very straight line if the medium was an absorber. So I get the impression that 97% of the atmosphere does not readily absorb IR, but I've never seen this actually stated. Is this the case?
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  5. RSVP, O2 and N2 molecules have no dipole moment and do not absorb IR radiation.
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  6. Riccardo: Thank you for your answer. I assume the ability to absorb IR is equal to the ability to emit IR. If this is true, how then do the gases O2 and N2 generally warm up or cool down?
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  7. Riccardo: I didnt quite phrase my question correctly. The concern is not so much how these gases warm or cool, but how the energy of these gases is eliminated from the Earth.
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  8. RSVP, I thought your question was related to light absorption by molecular vibrations. If you consider the gas as a whole, it will emit as appropiate to its temperature and emissivity. Not much energy, given the low average temperature and low emissivity. A good example is the atmosphere above the troposphere, where there's no convection and the atmosphere is in (almost) purely radiative equilibrium.
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  9. Riccardo This is what I suspected. My sense is that GHG's explain how the atmosphere has comes up to temperature since O2 and N2 would otherwise only warm through convection off the Earth's surface, and I assume that this has been deemed or calculated as not sufficient to explain current temperatures. If these gases are not good radiators of IR, and as they make up the bulk of our atmosphere, it should be fair to say they are responsible for holding (or storing) energy at some ambient level. For this same reason, the direct heating of these gases through industrial waste heat should be accumulating in these gases as well, and possibly the only way for it to cool is actually via GHG's, as they emit IR.
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  10. #34 and 38: I have to agree with Joe Blog here. I was dinged during my comps for making a statement similar to "As greenhouse gases stop heat from reaching the upper atmosphere, a distinct greenhouse signature is a warming lower atmosphere and cooling upper atmosphere." The key is that the energy balance of the stratosphere is dominated by the absorption of UV radiation from the sun, not IR radiation (or conduction) from below. This is why (as Joe noted) it has an increasing temperature profile with height. The outgoing portion of the energy balance is restricted. The stratosphere has no clouds to speak of and little water vapour, and so outgoing radiation is dominated by IR emission from CO2. Increasing the CO2 concentration greatly increases the efficiency of the stratosphere as an emitter of IR radiation. It doesn't matter whether that radiation goes up or down; what matters is it carries energy out of the stratosphere (causing cooling). Ozone depletion has a cooling effect. Increased heat trapping in the troposphere has an effect (but only in the transient case!). Both are much smaller than the direct effects of increasing stratospheric CO2. None of this, btw, contradicts anything said in John's fine pamphlet, which doesn't specify the relationship between increased CO2 and stratospheric cooling.
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  11. Adam C at 01:51 In the pamphlet it is worded as this IDENTIFYING THE GREENHOUSE SIGNATURE "The greenhouse effect leaves a clear signature in the atmosphere. Greenhouse gases stop heat from reaching the upper atmosphere. So we expect to see warming in the lower atmosphere(troposphere). And cooling in the upper atmosphere (stratosphere). This is exactly what we observe. There have been three people in this thread who have taken it literally as it is written, and id dare say the commentators here are more scientifically literate than the general public. It is a minor point, but i think the wording could have been better. One of those things i suppose, youve gotta keep the message simple enough to be understood. And stratospheric cooling due to increases in anthropogenic co2 is a lil less simple, than you can explain in one or two sentences.
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  12. doug_bostrom at 09:30 AM, doug, it is always about the NETT flow, at least in the real world, which is what I am only interested in. What you are arguing is the situation in a theoretical world in a theoretical state of equilibrium. You also appear to be arguing that although molecules are composed of electrical charged particles, their behaviour is not subject to the forces of the greater electromagnetic field in which the molecule in question resides. It is not about photons choosing direction, it's about molecules being able to sense the state of that surrounding electromagnetic environment. As the temperature of a body rises, the frequency at which it radiates thermal energy increases, thus a molecule not in equilibrium, but at a lower temperature, is being bombarded by energy at a higher frequency than it can emit at from in the direction that the higher frequency energy originates from. There are a couple of basic points that need to be appreciated:- 1. energy can only be transferred by heat between bodies of different temperatures, thus, obviously, at equilibrium no transfer occurs. 2. the transfer only occurs in the direction of the colder body, be it by radiation, conduction or convection. 3.radiation is the transfer of energy by heat. Unless one of the about points is not true, then by putting them all together it appears that if there is no transfer of energy, remembering that transfer can only occur in the direction from a warmer body to a cooler body, then there has been no radiation, again remembering that radiation is the transfer of energy by heat.
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  13. 1. energy can only be transferred by heat between bodies of different temperatures, thus, obviously, at equilibrium no transfer occurs. Id put it more as, that at equilibrium, energy transfer is balanced... it dosnt stop molecules radiating when they are at the same state as their neighbors... equilibrium by definition is a balance, a molecule will be receiving what its emitting. 2. the transfer only occurs in the direction of the colder body, be it by radiation, conduction or convection. Well, no not really, energy transfer by radiation will be in all directions, with the net flow of energy being from hotter to colder... A thermally "hot" system, will loose energy faster the greater the differential between its state, and its neighbors. 3.radiation is the transfer of energy by heat.
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  14. 3.radiation is the transfer of energy by heat. I didnt really want to go here, because its just semantics... technically speaking, heat in thermodynamics is a measure of the net flow of energy between systems... so by definition, heat can only be one way.... Radiation, on the other hand, is not directional. Radiation is a form of energy transfer.
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  15. Here's what you originally said, JohnD: robhon at 02:23 AM, the radiation of heat is always in one direction, from the warmer body to the cooler. That's wrong, because of your use of the term "radiation." Now you elaborate and your explanation actually becomes worse, but this is helpful because leaving all my spleen aside I think you're on the cusp of understanding something important: 1. energy can only be transferred by heat between bodies of different temperatures, thus, obviously, at equilibrium no transfer occurs. Ok, if you mean to exclude radiation as a transfer means. You don't: 2. the transfer only occurs in the direction of the colder body, be it by radiation, conduction or convection. You still seem to be harboring your fallacy about radiation. In reality, since we know that photons are not endowed with what you essentially visualize as knowledge of what will happen to them in the future, they can and indeed will be emitted from a cooler body and traveling in the direction of a warmer body if such a body stands in their path upon emission. Upon arrival there's a statistical probability they will transfer some quantum of energy to that warmer body, raising its temperature. If you can get your head around this concept you'll understand how the so-called greenhouse effect can raise the surface temperature of the planet.
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  16. Johnd, you have your terminology and concepts confused, especially in that point #3. In TD, heat is the net energy flow, that's correct, so it is not a mean of transfer. Energy transfer can occur in any direction but heat only flows to the colder body. Radiation is a way to transfer energy but it is not heat in itself. Energy can be transfered by radiation, conduction, convection. Multiple transfers can be occurring at equilibrium, as along as the net flow is zero (i.e. TOA incoming and outgoing radiation).
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  17. I think the author has been misled. Figure 1 in the 'Scientific Guide' should be looked at very carefully because the temperature scale is red at zero. That means if there had been no heating at all in the claimed 'hot spot' it would still be red!
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  18. Zero marks the boundary between orange and red. It is still clear in the figure that the troposphere is warming. The "hot spot" label may not be appropriate to this figure, however, since the figure is trying to highlight the contrast between troposphere and stratosphere, not that between surface and tropical mid-troposphere.
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  19. Hi all. New here :0) Love the booklet. Was wondering about other evidence. Like the increase in co2 correlation with decrease in atmospheric oxygen pointing to the combustion process as source for co2. And also the carbon isotope that points to it's origins from plant take up during photosynthesis and hence released when burned. Pardon my lack of sources. I think I read about them on real climate or a few things I'll considered. I am not a scientist so could these also be explained in your booklet?
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    Response: Good points. I cover these (among many) in the human fingerprint on global warming. The reason I don't cover them in the Scientific Guide is because it addresses a very narrow question - is there evidence that more CO2 causes warming? The Skeptics Handbook doesn't question whether humans are the cause of rising CO2 levels so in the interest of keeping the Guide tight and focused, I don't go borrowing trouble :-)
  20. hi john, Roger Pielke snr has incorporate my comment 32 and your response into his blog post: feedback on my invitation on the three hypotheses of climate It's at the end, his blog summarises feedback received about his 3 hypotheses. He has promised to respond to the feedback in a follow up blog.
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  21. Jo Nova recently reposted her handbook - apparently her site has received some attention in the news recently, and she wanted to call attention to her write-up. I commented there, and pointed people at some SKS threads, including The Scientific Guide to Global Warming Skepticism. I expect the number of thumbs-down on my post to soon reach the point of hiding my post, which paradoxically calls even more attention to it. John Cook - fantastic work on this site. I understand it's a labor of love, and what a labor it is. You are to be congratulated on your devotion to the future and to your children (and their children's children). I don't think that gets said often enough; Thank you.
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  22. KR, I second your props to John. Regular contributors to this site: See the Organizational Nominees at George Mason University's 2011 climate change communicator award. Vote early, vote often!
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  23. Has there been a rebuttal to JoNova's response? Her claim: "Indeed when I have bothered to debunk Cook, Cook had no reply, and didn’t apologize for all his errors, or his use of a flagrantly deceptive graph either."
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