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Climate Hustle

The Scientific Guide to Global Warming Skepticism

Posted on 8 December 2010 by John Cook

Scientific skepticism is healthy. In fact, science by its very nature is skeptical. Genuine skepticism means considering the full body of evidence before coming to a conclusion. However, when you take a close look at arguments expressing climate ‘skepticism’, what you often observe is cherry picking of pieces of evidence while rejecting any data that don’t fit the desired picture. This isn’t skepticism. It is ignoring facts and the science.

The Scientific Guide to Global Warming Skepticism looks at both the evidence that human activity is causing global warming and the ways that climate ‘skeptic’ arguments can mislead by presenting only small pieces of the puzzle rather than the full picture. 


The Guide explains the science in brief, plain language without getting too technical. For those who wish to dig deeper into the science, more detailed treatments can be found at the following pages (often presented with varying levels of complexity from Basic to Advanced):

How people are using the Guide

The Guide is being used by teacher associations, museums, websites, student groups and other organisations. Read some of the examples of how the Guide is being used.


To translate the Guide into another language, there is a two-column Word document plus a PDF Overview of the Guide to mark each section for translators. Please download the Word document and email me back the document with translated text. But first contact me to ensure noone else is already working on your language.

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Comments 51 to 67 out of 67:

  1. (a) CO2 and the oceans

    @John (reply@47)

    The caption says: “Warming causes the oceans to give up more CO2”.
    In your response you say “...more of our CO2 emissions remain in the atmosphere each year (the airborne fraction)”.

    To me these sound like very different propositions. One implies CO2 is leaving ocean and going into the air, the
    other suggests the ocean has reached its capacity and so no long takes up CO2 which therefore remains in the atmosphere.

    Conceptually that is completely different. Is this even the same phenonemon?
    Or are you saying that the first proposition is a quite of simplification that is not really accurate?
    Is this not confusing?

    @Rob Painting (@50)
    Thanks for your reply and the graphic. I take it that a positive flux of CO2 in the graph (red) means CO2 is leaving the ocean because it is warming.
    Negative (blue) means the ocean is taking up more CO2. When CO2 leaves the ocean, does this mean that the ocean becomes less acidic? Does warming offset
    the acidification problem to any extent?

    (b) The graph of ocean heat content

    @John (reply @ 47)

    You say "if he'd have had access to direct ocean heat measurements down to the abyssal depths, I'm guessing the ocean heat graph would've shown less year to year variability."

    I agree with you there. I think intuitively the graphs looks wrong. We are told on the one hand that the ocean stores most of the warming that is taking place, and then we get this graph which suggests that this ocean heat content is more variable than the heat content in the atmosphere.

    I'm still unsure about how reliable Murphy et al's data is given the problems with ocean heat content measurements discussed elsewhere in this site.

    @Eric (Skeptic) @ 49
    "So basically the ocean is storing heat over the long run but the rate of storage can fluctuate based on weather-related ENSO cycles in the Pacific."
    The problem, Eric, is that the fluctuations in heat content in the ocean suggested by the graph are way out of scale with what one would imagine. ENSO has a large effect on surface temperatures, but its influence on ocean temperatures should be proportionally far less than this graph suggests given its enormous heat capacity.

    I hope you can see now the problem with the way this particular graph is included in the guide. There are far too many questions about it. You do at least need more information about it perhaps a link to a page on your own site in the reference section explaining what it is AND WHAT IT IS NOT. These things come back to haunt.

    Thanks for your efforts. We are making progress.
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  2. Apologies for all the typos above(51). I hit "submit" instead of "preview". I hope it is still intelligible.
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  3. When CO2 leaves the ocean, does this mean that the ocean becomes less acidic?

    Yes, generally speaking the tropical regions are more alkaline than more temperate regions, because of the decreased solubility of CO2 in warm water. But remember that we are adding more and more CO2 to the atmosphere all the time, so the partial pressure also goes up, driving more CO2 into the ocean and so increase its' capacity to store CO2.

    Does warming offset the acidification problem to any extent?

    Not to any useful degree, as explained above. Ocean warming has its' own set of worrying consequences, but staying on topic, the oceans still have the capacity to absorb considerably more CO2, just depends how much more it we dump into the atmosphere.
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  4. Rob @ 53
    Thanks for those points. I see that it is complicated. On the one hand warming of ocean decreases its ability to dissolve CO2. On the other hand increasing CO2 in atmosphere increases the ocean's "ability" to store CO2. The question arises then about the relative scale of each of these affects to determine which one over-rides the other - when and where. And I'm still having trouble imagining the acidity problem against this complex background and I still don't know if I feel confident telling people that warming releases CO2 from oceans (overall). Perhaps it's a timing thing.
    This is probably not the place for explaining all of this stuff. If anyone knows a particular site or source where all of this is well explained or more suited to these kinds of questions, please let me know.
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  5. Paul Barry, this chart shows how El Nino depletes the tropical pacific ocean heat and La Nina recharges it. What is notable is that each strong La Nina recharge seems to provide a "step up" in tropical pacific heat content. Also it is not hard to imagine that as the heat of each El Nino gets spread around the world, the other oceans store some of that heat in the following year or two.

    That chart came from this page by skeptic Bob Tisdale Some of his work has been criticized here before, but that chart is just data.
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  6. Paul Barry The question arises then about the relative scale of each of these affects to determine which one over-rides the other - when and where.

    Precisely, hence the use of ocean circulation models to address this issue. A couple of simplified points though:

    - the heat capacity of the oceans is very large compared to the atmosphere, therefore the average increase in ocean temperature over the next century will be small (relatively speaking here - it'll be huge to the climate & marine life). In other words the oceans as a whole can absorb a huge amount of heat before there is a significant change in temperature. IIRC a 2 degree C rise in mean global surface ocean temperature by the end of the century, according to ocean circulation model projections (under business-as-usual scenarios).

    - The NOAA CO2 flux graphic represents variations in upper ocean water temperature that are many times larger than 2 degrees C. Ocean temperatures can vary by more than 30 degrees C. See surface temp graphic for instance:

    Does that help you reconcile the NOAA graphic with anticipated ocean warming this century?. The scales are different.

    Perhaps the easiest explanation for your skeptic/uninformed friends is that pH of the ocean was lower in the past, and the ocean warmer, when surface temperatures and CO2 concentrations were higher than today. If the warmth is supposed to mitigate the effects of acidification, why didn't it do so in the past?. Yeah, I know could lead to more skeptic arguments on acidification, but see link below.

    If anyone knows a particular site or source where all of this is well explained or more suited to these kinds of questions, please let me know.

    Try here - European Project on Ocean Acidification . Answers all the typical "skeptic"questions. Even addresses your temperature vs. acidification query.
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  7. Eric,

    Thanks for that additional graph. It follows with what has been said in the comments above. I've no trouble imagining how ENSO causes variability - steps in the progression of ocean warming. The problem is still the relative scale of these steps.

    Rob Painting,

    I think you agree with that too. Of course I'm not skeptical about ocean warming. It's happening. I just want it to see it presented realistically. We know how 'skeptics' behave when they see graphs that are questionable. That graph based on Murphy et al is, I'm afraid, not very realistic.

    Thanks especially for that last link which I think covers the issue of ocean acidification well. I don't think there is anything wrong with reproducing the particular FAQ entry from that site here which I think is a good explanation. I particularly like the way he throws in some numbers too to give you a sense of proportion:

    Won’t the CO2 outgas as the oceans begin to warm up, therefore cancelling out the problem?
    The CO2 content of the surface waters of the oceans responds to both changes in CO2 content of the atmosphere and changes in temperature.   For example, if ocean temperatures were not changing, a doubling of preindustrial CO2 levels (from 280 to 560 ppm) would cause an increase in the total amount of dissolved carbon in the surface ocean from about 2002 to 2131 micromoles/kg of seawater (assuming salinity = 35, temperature = 15°C, and alkalinity = 2300 micromoles/kg).  If ocean temperatures warmed by 2°C over that period, then less carbon would be taken up (the increase would be from 2002 to 2117 micromoles/kg).  Thus, a 2°C increase in temperature results in about a 10% decrease in carbon uptake in surface waters. The expected warming of the oceans also may alter ocean circulation, further reducing their capacity to absorb CO2 from the atmosphere, but the excess CO2 will still remain in the atmosphere and drive further acidification. For pH, the net effects of climate warming on atmospheric CO2, CO2 solubility, and chemical speciation approximately cancel out. — Scott Doney, Senior Scientist, Woods Hole Oceanographic Institution, USA; Joan Kleypas, Scientist III, National Center for Atmospheric Research, USA

    The problem of this apparent contradiction being a stumbling block probably won't arise too often (it's nothing near a killer argument for overall climate-change denial), but if we can answer these kinds question easily without getting grumpy and defensive it does wonders for our ability to convince others that we might know what we are talking about.

    Something has been achieved here. I think a Skeptical Science guest blog on the complexity of CO2/ocean interaction is in order!

    Many thanks to all.
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  8. I've just been looking at that graph again that shows ocean heat content increase. It came with today's blog-post. I see now that the data for ocean heat build-up come from Domingues et al(2008) - rather than Murphy et al(2009). So I guess that means a slight correction to the references section of the Guide is necessary. No big deal.

    It has just dawned on me now that I was interpreting this graph wrongly in my comments above. I see now that it's a graph of the heat anomaly, measured compared to 1950, not a graph of the absolute heat content of the ocean. Duh!

    My apologies for this error on my part and for taking up so much of your time. I'm now largely happy with the graph. I now think it is quite realistic. I don't think the bumps are so out of scale anymore.

    PS: I guess what threw me was the title: "Build-up in Earth's Total heat Content" . This made me think in terms of absolute accumulated heat (which I can see now it couldn't possibly be). Perhaps a little note to explain this distinction might help others to avoid the same confusion. In any case I take full responsibility for that misunderstanding! I hope I didn't lead too many people astray. Keep up the great work!
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  9. As evangelical Christian, I would like to thank you for this site and this guide. I have too many friends who are anti science and think global warming is a left wing conspiracy.
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  10. Thanks for a really, really nice, condenced and easy to read small document. It is a good hope of getting lesser educated or missinformed friends and colleagues to read this on such and important subject.

    I've got a comment on page 4, where the upper right figure is showing the amount of build up of the Earth's total heat content.

    I think that either the text: "Ocean Heating" should have said: "Glaciar Melting and Ocean heating", if that is the case. If that is not part of the graph, the accumulated heat made by Glaciar Melting could be added as another factor?

    When knowing that the heat energy needed for melting 1 kg of ice, could otherwise increase the temperature of 1 kg of water with nearly 80 degrees Celsius (if I got the numbers right?) the spent energy (heat) for melting thousands of km3 of glaciers during the same periode is enormous.

    If I'm remember right, the netto ice-loss on Greenland alone is more than 100 km3 annually?
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  11. Although I am impressed at the quality of the Guide, and the zeal of the translators, I really don't think additional translations are really going to help very much. It is not the kind of effort we really need, since the perps who are destroying our environment are perfectly competent at reading English.

    However, the two languages that are most likely to do some good are 1) Russian, since Putin and Medvedev are eager to sell as much oil as they can, and 2) Mandarin Chinese, since it was the Chinese who sabotaged Copenhagen, together with the Indians.

    Of course, the Indians are a perfect example of those who already have the science in a language they can understand -- and they choose to ignore it. I am sure most people here in this forum realize that English IS "the international language of India". They even prefer it over their own language when communicating many fellow Indians since it avoids the political implications of forcing non-Hindi speakers to speak Hindi.

    Now of those two languages, I think Mandarin is actually the higher priority. Just think of the publicity for the cause when we discover the Chinese Government is blocking access to the guide because the evidence is so damning against them!
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  12. BTW: every time I see the statement, true though it is, that "Scientific skepticism is healthy", I want to follow it immediately with "unscientific skepticism is unhealthy, even poisonous."

    That way, the point of your first paragraph could almost fit on a Prius bumper sticker;)
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  13. I was looking to commit the booklet to paper, but it needs to be done in colour to preserve the graphics, but much of the text will look terrible on paper. Any chance of a printable version?
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    Moderator Response: [DB] Try here.
  14. It might make sense to replace your Fingerprint #1 with this site's argument that extra CO2 comes from oxidation of fossil fuels (to which I just posted a comment about fixing broken URLs). The falling-O2 argument may be easier to understand. Also, the O2 argument makes a stronger claim, that O2 is going down by the same amount that CO2 is going up.
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  15. Regarding Kiwiiano's comment above, I think that he/she was asking for a high resolution PDF, rather than for a printer friendly version of the download page.
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  16. Skeptical Science is a strong brand - has there been any discussion related to using the framework and name for other areas in need of science communication (I'm thinking vaccines and GMOs for starters)?

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  17. I would be happy to assist in the translation of this guide in Greek. Please notify me, if you are interested.

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