Credibility Spectrum

Let’s face it, there’s a lot of “climate science” out there that’s absolute rubbish.

Type “climate change” into Google. Within seconds you can find statements that the Earth is warming or that its temperatue is stable (or cooling since 1998!). You can find “proof” that the warming is caused by the sun, volcanoes, flaws in the temperature data, or fossil fuel burning. You can read that the Hockey Stick graph is broadly accurate, or that it was manipulated by the IPCC to agree with a predetermined conclusion.

Whatever you read about climate change, chances are that there’s another source saying the opposite thing. It’s not like we’re all climatologists who can see straight through misinformation. So how do you possibly sort out what to believe?

When people ask me this question, I invariably respond with, “Assess the credibility.”

The ”climate change analysis” you read could be from a national academy of science, or from a blogger. It could be from an atmospheric physicist or a economist. It could be from a scientific journal or a political think-tank. If we calculate credibility to be “expertise + objectivity”, it’s obvious that some sources merit more weight than others.

I’ve put together a climate change credibility spectrum, inspired by Greg Craven from the Manpollo Project. This is a basic way to assess credibility and assign weight to a source. Keep in mind that it is only used for scientific statements, like “Arctic summer sea ice will be gone by 2030″. Matters of policy, like “we should adopt a cap-and-trade system”, are on a much more equal playing field – because they’re opinions, not facts.

The credibility spectrum is sort of split into two: the scientific community, and the non-scientific community.

The scientific community starts with scientists, and I want to stress that this category only includes scientists with experience in the issue at hand. Just because someone has a PhD in one area of science doesn’t mean that they are an expert in all areas. For example, it’s very easy for a computer scientist to go through ten years of university without studying any biology at all.  Treating them as an expert in evolution, therefore, would be illogical.

These scientists write peer-reviewed papers, published in journals like Nature and Science, which are another step up the credibility spectrum. Instead of just having the name of an expert attached to them, their methods and conclusions have been evaluated for robustness and accuracy. This is the minimum level of credibility from which I recommend citing scientific claims.

However, as thousands of papers are published every month, and they’re generally studying the frontier of their field, it’s inevitable that some of them will be proven wrong later. As climatologists Gavin Schmidt and Michael Mann wisely said, peer review is a necessary but not sufficient condition.

That’s why there are scientific organizations and assessment reports, like NASA or the IPCC, which compile peer-reviewed knowledge which has stood the test of time into consensus statements. Even the top level of the credibility spectrum isn’t infallible, but it sure has a low error rate compared to other sources.

Everyone who isn’t a scientist, which is most of us, falls into the lower half of the credibility spectrum. The category I refer to as “communicators” includes the mainstream media, projects like Manpollo or, high school teachers, politicians…….They’re not part of the scientific community, so you should always check their citations, but they’re held more accountable for what they say than just any random person on the street. If they make glaring errors, people will be more upset than if the same errors were made by individuals – comments on YouTube, discussions with your neighbours – which make up the lowest rung of our credibility spectrum.

Something that I found really interesting  when I put this together was the general flow of information between different sources. In the scientific community, research starts with scientists, and the best research is published in journals, and the best journal articles are picked up by major organizations. As the scientific knowledge progresses through the different sources, the weaker assertions are weeded out along the way. The flow of information is going up the pyramid, towards the narrower part of the pyramid, so that only the best is retained.

However, in the non-scientific community, the flow of information goes the other way. Communicators present information to individuals, which is a much larger group. Information travelling down the pyramid, instead of up, allow rumours and misconceptions to flourish much more easily.

This isn’t to say that, when they come head-to-head, organizations are always right and individuals are always wrong. But given the history of such disagreements, and the levels of credibility involved, you’ll know where to place your bets.


49 thoughts on “Credibility Spectrum

    • I’m reading it right now and will do a review when I finish, hopefully by the end of this week. I like it so far but I think it puts a little too much trust in people to be logical and just. I know a lot of people who would refuse to think that way simply because it might get them a conclusion they don’t like. The How it All Ends series was better, in my opinion, he wasn’t so ridiculously non-partisan.

  1. ‘Ridiculously non-partisan’?

    I haven’t read Greg’s book (‘What’s the Worst That Could Happen’) yet myself — I’m still, ironically, waiting for the archaic systems of the carbon-wasting publisher to ship the books to Blighty.

    I’m not very good myself at persuading others with entrenched ideas on a subject (I tend to rant too much). I gave it a shot with Dvorak -vs- QWERTY and didn’t get very far with that.

    It seems to me that to have any chance at all of opening a dialogue with someone who may be entirely oblivious of suffering from a knee-jerk reflex is to bend over backwards to not trigger the reflex. Either that, or chop the knees off, maybe :)

  2. Outstanding. It’s been impossible for me to find a site wherein the author is informed and disciplined by the scientific method. I’d belong at the bottom of this spectrum. But I’d be somewhat higher on the spectrum of expertise viz the capacity to promote propaganda, I’m a copywriter, and the PR Machine on AGW is something that’d strike Beria green with envy.

  3. Thanks Adrien, I’m glad that you like what I have to say. I agree that the “PR Machine on AGW” is quite brilliant. I wish we had them on our side. We’d all be driving hydrogen cars by now.

  4. Eh, where do textbooks stand in this hierarchy?

    (And I mean real textbooks, not the books they produce for schools, but, you know, summaries of the state of the science by active researchers; perhaps “monographs” is the term).

    • I’m not quite sure what you mean by these kind of textbooks, I don’t think I’ve encountered one yet in my studies, do you have an example?

      I’d guess that they’d fall somewhere around universities, just below peer-reviewed articles.

  5. Dear Kate:

    I read about your blog on Yahoo news, and it is very interesting. Now here is my two cents, if I may….

    It is a common fact that great minds think alike, in other words, all great scientific minds think alike. Another way to say it is, WHEN all great minds think alike, then there is the possibility of tunnel vision or narrow mindedness.

    It may be true that most scientists believes that global warming is caused by humans, but is it absolutely true? Or is because those scientists were taught this fact without question the contrary?

    What if ONE great scientific mind says global warming is not true? Would that be Heresy to the scientific community. Would that leads to destablization of the scientific community and lost of jobs and faith in science? Think of all those scientists who would be unemployed after a lifetime of hard work through tunnel vision. Think of the kids of those would be unemployed scientists if this Heresy becomes public.

    Therefore, it is better to believe in one another then to rock the boat of this “Global Warming” theory.

    Just my two cents.

    [Science doesn’t really work that way. It doesn’t matter what you say, it only matters how you prove it. The means justify the ends. And you’d be hard-pressed to find a real scientist who would hold a scientific belief that they couldn’t prove, or would continue this belief if contrary evidence came out (real contrary evidence, not fluff like “global warming stopped in 1998). -Kate]

  6. what dose credibility mean!? ive looked everywhere for the answer

    [Credibility is a measure of how much you can trust what a source tells you – eg, what NASA says about the moon is more credible than what your bus driver says about the moon. You can trust them more, because there’s a greater chance that they are giving you accurate information. Greg Craven has a great video about science and credibility, in three parts starting here. -Kate]

  7. I just discovered this site while reading about Canada’s deplorable lack of action at Copenhagen. I find it odd that we’re still bothering to debate whether climate change is fact or myth when all around us our Earth is being degraded. Why are we arguing? We all live here. Whether or not the science backs what we can percieve with our own senses, we are all subject to the devastating changes that are taking place.

  8. In your reply to Pan you wrote:

    [Science doesn’t really work that way. It doesn’t matter what you say, it only matters how you prove it. The means justify the ends. And you’d be hard-pressed to find a real scientist who would hold a scientific belief that they couldn’t prove, or would continue this belief if contrary evidence came out (real contrary evidence, not fluff like “global warming stopped in 1998). -Kate]

    First, nothing is ever “proven” outside of logic. Things are just accepted to be true on the basis of compelling evidence. But accepting a more fuzzy meaning of “prove”, it’s also true that 99% of what most real scientists believe they couldn’t prove – they take the word of the experts in the domain.

    It’s also true that most of science is accepted because it “works” – if your theory is right (or ‘right enough’, you can successfully manipulate the world on that basis. The fact that we have an Internet is based on a very successful research program in physics (and it doesn’t depend on whether string theory turns out to be true or not).

    Part of what makes climate change so difficult is that the much of what is most important can’t be tested with laboratory experiments, or turned into marketable products (or weapons). So the kinds of “proof” that we’re really used to aren’t available. I encourage you to look into the work of Sylvio Funtowicz and Jerry Ravetz on “post-normal science” in this regard.


    –Paul Baer

    ps “temperatue” is misspelled in the third paragraph

  9. As a climate scientist (I reconstruct climates of the past using the fossil record; search for the terms ‘climate proxies’), I am always puzzled by comments like ‘climate change isn’t proven’. The so-called lack of ‘proof’ for climate change is a complete fallacy. Climate is always changing, and has been throughout earth history. If there is any debate, it is over the cause of that climate change.

    For most of earth’s more than 4 billion years of history it has been ice-free at one or both poles. Having ice-covered north and south poles is the ‘normal’ state for the past 2.5 million years, with Antarctic ice likely for the last 40 million years. The northern polar ice-cap has oscillated in size over the last 2 million years (the glacial-interglacial cycles of the Pleistocene Epoch). That oscillation was due primarily to changes in earth’s orbit around the sun (Milankovitch cycles; google for an explanation), a process that has been going on throughout earth’s history. What is different about the last 2-3 million years, and also the last 200 years, is the level of CO2 in the atmosphere.

    There are many natural causes for fluctuations in CO2 levels: volcanoes produce both ash (which acts as a temporary coolant) and CO2; marine organisms fix CO2 in their shells which fall to the ocean floor and in the right setting get turned into limestone or other carbonate rocks, ditto coral reefs. As the tectonic plates grind their way under each other at subduction zones, any carbonate rocks are melted and the resulting CO2 is vented by volcanoes. If these same limestones are uplifted on land by mountain building, erosion of those rocks also releases CO2 into the atmosphere. When large areas of peat-accumulating swamps are buried, additional carbon is trapped and forms coal. Accumulating organic matter in oceanic sediments may become oil and gas deposits. This is the carbon cycle and it also incorporates land-based plant photosynthesis and animal respiration, decay etc., but these are minor components of the carbon cycle compared to the volcano-mountain erosion marine limestone story and the formation of hydrocarbon reservoirs (see any intro geology textbook). It is the understanding of the power of the carbon cycle and the primary role played by geological processes that promotes doubt in some geologists minds that present-day climate change is caused by human-sourced CO2 in the atmosphere; they simply don’t believe that we humans have that much influence. I disagree.

    Prior to about 4 million years ago (Pliocene epoch and older), CO2 by most lines of evidence sat somewhere about 400-2000 ppm (parts per million) in the atmosphere, and may have been much higher at times. 50-55 million years ago when both poles were forested, CO2 was about 600-800ppm (see Zachos et al. 2008, in Nature vol. 451, January 17th, or google ‘Eocene climate’; several scientific papers on this topic will be coming out over the next couple of months). Throughout the Pleistocene ice-ages CO2 varied in the range 120ppm (glacials) and 280ppm (interglacials). It sits now at about 389ppm, according to NOAA values (see Present-day levels of CO2 are well established as being from burning fossil fuels and other human activities; a shift from 280 to 389ppm in 150 or so years.

    The question really isn’t ‘where did the CO2 come from’, so much as where did it go in the past. You see for most of earth history CO2 has been high. The last 2-3 million years have been an anomaly, with low CO2 the norm. Coal-forming, limestone forming, and similar processes appear to have stored massive amounts of CO2 over the last 50 million years. This period coincides with the appearance of grasslands (a major shift in vegetative cover, with consequences for the albedo of the earth’s surface, hydrology, and for how much carbon is trapped in soils), as well as the period when the Himalayas, Andes and Rocky Mountains were pushed up. Eroding mountains can trap CO2 when it is dissolved in rainwater (I over-simplify).

    When CO2 falls below critical thresholds, its influence as a greenhouse gas is overshadowed by other processes, such as orbital shape (Milankovitch cycles). Under lower than 400ppm, the shape of the earth’s orbit became the primary influence, and ice ages resulted. So, we’re busy burning coal, oil and gas that represents carbon dioxide that was fixed by plants and algae on land (coal) and the oceans (most oil and gas) millions of years ago; this was stated by Revell & Suess in 1957, who warned then that releasing all this old CO2 would push up global temperatures. That addition of old CO2 into the atmosphere is returning the atmosphere to a CO2 level it hasn’t seen for at least 4 million years (again, what Revell & Suess said in 1957; watch out for a paper in the scientific journal ‘Geology’ in July on this topic), and ultimately to levels last seen in the Eocene, 50-55 million years ago. 4 million years ago, under CO2 levels a little higher than today, boreal forests extended as far north as northern Ellesmere Island (see Tedford & Harington, 2003 in Nature vol. 425, pp. 388-390); 45 million years ago, these same forests were subtropical. That is our future under a ‘business as usual’ carbon dioxide policy. We can’t influcene astronomical and geological processes, but we can influence how much CO2 is in the atmosphere. That is why we should act now.

    All of the above is not conjecture, nor is it my personal theory or someone else’s that I have repeated. It is the current understanding backed up by many scientific papers published over the last 20 years, and especially the last 5 years. I have cited a few here.

    Thank you, David, for that great explanation of the current knowledge of the paleo field. It gives us lots to chew over and think about. I am excited to read the paper in Geology this July. In 2009 a paper in Science by Honisch et al found that CO2 is higher now than in the past 2 million years…..and now that estimate is potentially doubling. Scary stuff, why are the revisions to these estimates always in the direction of things getting worse?! -Kate

  10. Hi Kate

    I started my career as a climate change skeptic; I was even quoted in an Australian newspaper reviewing my research as stating this. Through my own research on climates of the geological past, and through reading the literature as new things were discovered, and attending conferences where the science was presented and debated, I changed my opinion. That’s the key point about science, and your credibility spectrum; science and scientists do change their mind on the basis of evidence and the best understanding as it is developed. My research is funded by the Canadian government (NSERC), and my grants don’t depend in any way on my taking any particular position on climate change. Results (= publications and students trained) are what matters. Yet time and again I see climate change deniers (including some of my own students) accuse climate change science as pushing an agenda to secure research grants; there is sometimes a mistaken notion that somehow scientists personally benefit from these dollars. The truth is that research dollars would flow to any scientist who published scientific studies refuting climate change, provided it was good science, just as much as they do to good science demonstrating climate change.


    Many scientists started out as skeptics, but the evidence convinced them. That’s probably the best way to go about it, given the nature of science – be skeptical about everything, but change your mind when necessary. Be skeptical about your skepticism.

    One of my favourite discussion threads on this blog had a lot to do with changing your opinion based on evidence, you can read it here.

    Regarding the impact of grant money on a scientists’ salary – read Scott Mandia’s awesome breakdown of this myth, part 1 and part 2. -Kate

  11. Hmmm. So the proportion of carbon dioxide was as low as 120 ppm not so very long ago.

    At what level does photosynthesis shut down, Mr. Greenwood?

    (Hint: it’s not much lower than 120. Makes you think.)

  12. Harry Eagar asked how low can plants go with CO2 before photosynthesis shuts down. I found this site that indicates that for some types of plants the minimum CO2 level (compensation point, that is, where CO2 produced by the plant’s cell respiration equals that made by photosynthesis) is somewhere lower than 100 ml/litre (equivalent to 100ppm).

    120ppm (the levels during the ice-ages of the past 2 million years) is very low. In most situations in nature the limits on plant growth are soil fertility and water supply, not CO2.

    Photosynthesis is limited usually by the supply of light (right amount and duration as it takes time for the plant cells to make the important enzyme Rubisco – this isn’t stored as it is costly for the plant to make). Plants respond to differences in how much CO2 is in the air by varying the frequency (number per unit area) of the pores on the leaf surface (called stomates). These pores can be opened or closed, and act to control the loss of water from the leaf, yet allow CO2 in. Plants must lose some water as the loss of water is part of the energy driving uptake of water and dissolved nutrients from soil. So all plants must balance water loss and CO2 uptake from their leaves. Under higher CO2, plants have improved water use efficiency as they get more CO2 for every unit of water lost (this is why some commercial greenhouses deliberately increase CO2). Some scientists have speculated that crops will have higher yields under a higher CO2 atm,osphere. Unfortunately, many scientific trials have shown that whereas plants do grow faster and often larger under high CO2, they often have lower protein levels so are less useful as food.

    This website is also a good resource but may be too technical for some:

  13. On the subject of plants, the experimental evidence (open top and recreating conditions expected under projected GHG emissions) indicates that grasses and crops suffer.

    UC Davis’ press release:

    Data from all five methods confirm that elevated levels of carbon dioxide inhibit nitrate assimilation in wheat and Arabidopsis plants. The researchers note that this effect could explain why earlier studies by other researchers have documented a 7.4-percent to 11-percent decrease in wheat grain protein and a 20-percent decrease in total Arabidopsis protein under elevated carbon dioxide levels.

    “This indicates that as atmospheric carbon dioxide concentrations rise and nitrate assimilation in plant tissues diminishes, crops will become depleted in organic nitrogen compounds, including protein, and food quality will suffer,” Bloom said. “Increasing nitrogen fertilization might compensate for slower nitrate assimilation rates, but this might not be economically or environmentally feasible.”


    …But an unprecedented three-year experiment conducted at Stanford University is raising questions about that long-held assumption. Writing in the journal Science, researchers concluded that elevated atmospheric CO2 actually reduces plant growth when combined with other likely consequences of climate change — namely, higher temperatures, increased precipitation or increased nitrogen deposits in the soil.
    “Most studies have looked at the effects of CO2 on plants in pots or on very simple ecosystems and concluded that plants are going to grow faster in the future,” said Field, co-author of the Science study. “We got exactly the same results when we applied CO2 alone, but when we factored in realistic treatments — warming, changes in nitrogen deposition, changes in precipitation — growth was actually suppressed.”

    One of the greatest objections to curbing CO2 emissions is the assumed benefits to plants, therefore crops. I find it hard to understand why so many ignore these actual experiments, preferring to refer to less appropriate “closed top” experiments which introduce extra CO2 alone.

    Have grasses ever thrived under higher CO2 conditions anyway? They seem to have been restricted to watersides for most of the species’ existence as far as I can tell, and it was when CO2 levels dropped that they spread to what we see now. I may be wrong on that last point as i don’t have the references I once read to hand.

    Thanks for that link. The “CO2 is plant food” meme is a very common misconception. However, as we see in studies such as the one you mentioned, CO2 fertilization is limited. For example, if the resulting warming limits the plant’s access to water, photosynthesis won’t increase, no matter how much CO2 is available. -Kate

  14. Kate, you and climatesight visitors may be interested in this research article I co-wrote just published in the science journal Geology. The research reports on our reconstruction of climate for Ellesmere Island in the Canadian high Arctic where we show that temperatures 4 to 5 million years ago were ~19C higher than today, at a time when atmospheric CO2 levels were very close to those today (~390ppm vs ~387ppm in 2009 from the Mauna Loa, Hawaii record: )

    The implication of our research is that we may already have passed a tipping point for major increases in Arctic temperatures due to increasing levels of atmospheric CO2. Our research is based on a fossil site on Ellesmere Island that shows Boreal forests (like those that span most of northern Canada south of the tree-line, and also Russia and Alaska and Scandanavia) were present, including larch, poplars, white cedar, and animals such as beavers, bears, deer, etc.

    The article is open access, so should be downloadable for free here:


    Congrats, David! That’s a really interesting publication. What were other climate forcings, such as solar/orbital, albedo, etc like during the Pliocene? Do we know if the radiative balance was in equilibrium? i.e., how closely can we use this period of time as an analogy for what will happen over the next few decades? -Kate

  15. Another paleoclimate paper putting temperatures at much higher then, when CO2 levels were comparable to now, or what’s projected for 2100. That’s one for Ari’s AGW Observer website, thanks.

    Here are some more from the past year or two, if anyone’s interested:

    Palaeoclimate: Global warmth with little extra CO2. Birgit Schneider & Ralph Schneider (2010).

    Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years. Tripati et al (December 2009)

    Earth system sensitivity inferred from Pliocene modelling and data. Lunt et al (December 2009)
    Here’s a chart

    High Earth-system climate sensitivity determined from Pliocene carbon dioxide concentrations. Pagani et al (December 2009)

    Atmospheric CO2 concentrations during ancient greenhouse climates were similar to those predicted for A.D. 2100. Breecker et al (October 2009)

  16. ‘120ppm (the levels during the ice-ages of the past 2 million years) is very low.’

    No kiddin’.

    I knew the answer before I asked the question, which is why I asked the question.

    I don’t think I’m looking forward to the natural experiment of seeing whether the next ice age will go below 120.

  17. Hi Kate

    I’m not a modeller, but my modeller colleagues tell me that the Pliocene is very useful as an analogy for the present / next 200 years as climate forcings, such as solar/orbital, albedo, and also the positions of the continents were very similar to today. There were, however, important differences to today (little or no ice at the north pole). There is a nice summary of how understanding Pliocene climates can assist our understanding of climate change in Chapter 6 of the IPCC report (see pages 440-442).

    Click to access ar4-wg1-chapter6.pdf


    2-3 C warmer at equilibrium, and sea levels 15-25 m higher than present….and that’s only from CO2 concentrations approximately equal to today’s. Yikes! Thanks for that link, it was interesting, if a bit scary. I enjoy looking at paleo analogues to our situation. -Kate

  18. First, loved that climate science overview, David, and would like much to post it on my website and blogs with the permission of you and Kate.


    Site: Linked above, I believe.

    As for the tipping point, this brings up one of my greatest frustrations with science and scientists. It was obvious to me four years ago climate was changing much, much faster than expected. I’ve had e-mail exchanges in private with scientists saying the sea bed clathrates simply couldn’t be a factor for a hundred years.

    We all know how that’s turned out.

    What is it about the current scientific community/culture that has beat the gut instinct out of so many such that they can only allow themselves to accept what data reveals and ignore intuitive knowledge?

    Science has been built on intuitive leaps, for goodness’ sake!

    Anywho, tipping points well crossed. Watch the melt going on. As goes the Arctic, so goes the planet. Full stop. Time is no longer short, it is up and we down to penalty kicks. Pray Mother Nature misses a few.

    I know of only three ways to draw down carbon, or at least reduce emissions, in a useful time frame.

    1. Plant the heck out of trees.

    2. Become not only a nation of farmers (S. Astyk, et al.), but a world of farmers. Specifically, organic, sustainable farmers and sequester carbon in soils. (Rodale Inst.)

    3. STOP burning everything in sight. I.e., paradigm change to smaller communities (Dunbar’s Number), walkable communities, renewable energy systems within, most likely, a steady-state-ish economy.


    You have my full permission to post David’s comment, if he’s willing. -Kate

  19. Birch, Larch Pine forests near the North Pole, mmmmm. Just where was the “North Pole” at this time? Would Continental Drift come into play?? And the magnetic poles?

    19 degrees C warmer is alot. Is that figure a yearly average? How cold was it in the winter? In the summer? Is that difference measured from todays averages?

    David, can you answer these questions for us, seeing as you were the author of the paper? -Kate

  20. Kate, what I especially liked about your original “credibility spectrum” post was that it had an intro, that explained for newcomers why it was important.

  21. Dealing with questions posed:

    1. yes, permission granted.

    2. And for winnipegman: The position of most of North America relative to the rotational or geographic north pole (the magnetic north moves around) is well understood. Ellesmere Island for most of the last 50 million years has been very close to where it is now, with the position of the fossil site in the Pliocene – the time of the study just published in Geology – essentially the same as today; 78deg N. So no role played by continental drift. Fossils of this age from Alaska indicate a very similar story.

    This paper by Salzman et al. 2008 is a little technical in places, and a little out of date (now), but provides a nice insight into why we should care about Pliocene climate, and also discusses our understanding of matches and mismatches between the world of the mid-Pliocene and today, and so why it is a useful analogy for our future. It should be open access, so free to view.


  22. I missed a question from winnipegman.

    “19 degrees C warmer is alot. Is that figure a yearly average? How cold was it in the winter? In the summer? Is that difference measured from todays averages?”

    The 19 degrees refers to ‘mean annual temperature’ or MAT which is as the name suggests is the yearly average. For reference, the MAT of Vancouver is about 9.9C, Winnipeg 2.3C, and Eureka Nunavut (a few 100km from the fossil site) is -19.1C. Our estimate for MAT averaged across 3 independent methods was about -0.4C with uncertainty of about 0.4C to 5C, depending on the method used. So ’19C warmer’ is the difference between our estimate and modern-day Eureka NT. All modern climate values are from Environment Canada’s climate normals online:

    We also estimated summer and winter temperatures. Winters were dramatically warmer than now (which is entirely logical; its extremes of cold that limit most plant and animal distributions) at -11.6C but with large uncertainty (+/- 7.1C) vs. -37.6C today at Eureka NT; summer was 14.4 +/- 2.0C vs. 5.7C today at Eureka, about 10C-14C warmer in summer. Trees only grow where summers are on average warmer than 10C, and this defines the northern treeline. If you want to find a modern equivalent, try Goose Bay in Labrador. Lots of snow in winter.

  23. “However, as thousands of papers are published every month, and they’re generally studying the frontier of their field, it’s inevitable that some of them will be proven wrong later. As Gavin Schmidt and Michael Mann wisely said, peer review is a necessary but not sufficient condition.”

    No, not “some” papers will be proven wrong – but many if not most. Although I cannot give you a citation, but the last quantitative one I can recall got the result that two-thirds of scientific papers are later overturned. (Obviously, estimates vary depending upon the sample and criteria.)

    A quick google search finds a New Scientist article cited a study claiming 50%.

    This fact (and its ilk) are important to keep in mind when claiming “peer review” as sufficient authority. It is reason enough to keep one’s critical lights on.

  24. Hi Kate

    I have previously commented on your blog about how various scientific professional societies in the US, Canada and Australia (and elsewhere) have developed position statements on climate change. For the unitiated, these professional societies represent scientists, and in the case of the Geological Society of America, that society includes many geologists who work for oil & gas and mining companies. GSA has a strong and long-standing relationship with those industries and receives financial support from them. Because this organization is composed of and governed by scientists (mostly geologists and geophysicists), GSA would sit high in the credibility spectrum.

    Given some of the arguments against AGW, and its close relationship with oil & gas and mining, some people might have expected that GSA may have adopted either a neutral or skeptical position on AGW. It is certainly true that some members of GSA are AGW skeptics, and some GSA members were contributors to the IPCC 2007 process. The AGW position statement on climate change was recently revised and I think readers of your blog would be interested to read this commentary piece in this month’s issue of the society’s newsletter ‘GSA Today’ by William F. Ruddiman (a paleoclimate researcher, like myself). Dr. Ruddiman in this commentary reflects on the process undertaken by the Panel set up by GSA to draft the revised GSA Position Statement on climate change. Of greatest interest, though, is their response to comments received from GSA’s membership (including comments by AGW skeptics) in response to the release of the draft Position Statement. In those responses, placed at the end of the piece together with citations of the science behind their responses, readers will find rebuttals for many of the concerns raised by geologists and other earth scientists over the science of AGW, and rejection of any bias or lack of expertise by the GSA Panel. Its a free to all PDF document download.

    Click to access i1052-5173-20-7-40.pdf

    The GSA Position Statements, including the one on climate change, can be found here:

    David G.

  25. Orson makes some fallacious arguments in his post that must be challenged as they are at the root of most attacks on the credibility of climate change science. The link includes this quote (I have numbered the list for convenience) and conclusion:

    “… a research finding is less likely to be true when

    1) the studies conducted in a field are smaller;
    2) when effect sizes are smaller;
    3) when there is a greater number and lesser preselection of tested relationships;
    4) where there is greater flexibility in designs, definitions, outcomes, and analytical modes;
    5) when there is greater financial and other interest and prejudice; and
    6) when more teams are involved in a scientific field in chase of statistical significance.”

    Simulations show that for most study designs and settings, it is more likely for a research claim to be false than true. Moreover, for many current scientific fields, claimed research findings may often be simply accurate measures of the prevailing bias. In this essay, I discuss the implications of these problems for the conduct and interpretation of research.”

    And then the poster sums up with “Note these characteristics closely fit climate science.”

    The last statement is so completely wrong it is laughable. The original article was primarily directed at medical science, not most physical science. There are important differences between medical research and almost any other area of science. let’s deal with them using the bulleted list provided.

    1) climate science today is not a ‘small field’; there are thousands of papers now published in this field – a quick scan of the references cited in the IPCC reports will attest to this, or type in ‘climate’ and ‘change or warming’ in a science search engine like Google Scholar (restricting your search to science areas) and see how many hits you get – I did and got 721,000.

    The article was directing this point at medical studies that focus on an obscure or rarely studied disease, where there are few researchers, and so fewer ‘peers’ to undertake critical review, and those few that there are may either be close colleagues or rivals.

    2) depending on the climate process being studied, the effects measured can be large. It is true that the published rate of temperature change averaged for the earth over the past 100 years is a fraction of a degree, but the temperature rise in the Arctic is a little over 2C in the past 50 years (; my recently published paper in the science journal Geology shows a 19C shift between the Pliocene (the last time in geological history when CO2 levels were the same as now) – not a ‘small effect’.

    In contrast, the effect of some chemiclas in the body may be at very small concentrations, or a new drug may have only minor efficacy in treating cancer, for example; the extra percent that survive with the treatment may be small, so at the margins of what can attributed to chance alone.

    3) and 4) studies of what pushes climate towards warming or cooling across the globe have explored a multitude of relationships and causal factors, so may be some issues here. Media coverage of climate change science focuses on CO2 as that is the area of intersection between science and politics that has most consequences for our lifestyles; energy use = CO2 output. The science that underpins the role played by CO2 has been understood for a long time (over 100 years). Climate models don’t just crank up CO2 and see what happens. They are now quite complex and factor in things like; variable output by the sun, variations in the earth’s orbit around the sun, greenhouse gases AND dust from volcanoes, greenhouse gases from decay in wetlands and from agriculture (rice paddies are artificial wetlands), differences in the reflectivity (‘albedo’) of different surfaces (grass reflects more sunlight than forest, and ice much more than open water etc.) … and there are many more. But my point here is that climate science isn’t focused on a small set of possible exaplantions; it is exploring many and studying their interactions.

    5) geez, this one comes up time and again. ‘We’re in it to make money.’ Gee, where did I park the sports car??? There is an excellent shattering of this myth on Scott Mandia’s blog ( see also his part II).

    Medical research does include some real pitfalls in this regard because, particularly in the USA, there are buckets of money to be made in medical research. That is why big-pharma hires lots of biochemists and molecular biologists and the like to do research, and that’s why your family doctor might give you a free sample of some new drug. I don’t know many corporations doing climate change research.

    6) this is about competition between scientific teams. It happens. But that is what the peer review process is for, and why it is usually anonymous reviewer. Is peer review perfect? No. But it works pretty damn well. Its also why almost every journal I review for posts an policy on ethical guidelines for both authors submitting papers and reviewers for their reviewing. yes, its something of an honour system, but most cases of scientific fraud have been in medical research (where the big money is …) and not in the physical sciences. Scientific fraud is sniffed out pretty quickly and would ruin any scientist stupid enough to try it.

    My final point is that many of the posts I have seen that pose questions like these are simply saying ‘we can’t trust the scientists’. This is the fruit of the AGW denialist campaign, and is oh so similar to what the tobacco companies tried in the 1960s-1970s; sow doubt, muddy the waters, and stave off the inevitable. Basically, we scientists are being called liars. If I wanted to make a career out of making stuff up and making decisions based on my ‘opinion’ or the consensus of my ‘friends’ on facebook or Twitter, or how many thumbs up I got on the Globe and Mail or CBC website or other blog, I would have become a politician. I’m not saying scientists opinions should be accepted blindly. Quite the opposite. But I am saying that there are so many checks and balances in the system that when an overwhelming majority of scientists come to the same conclusion, that should not be dismissed as rhetoric.

    Do you trust the laws of physics and metalurgy etc enough to fly in a plane? Do you accept that your GPS will direct you to your destination? Do you believe that taking a pain killer will ease your aches? Do you trust that the diagnosis for your disease more often than not will be correct, leading to a good outcome? Do you have house insurance? (the premium is determined from calculations of the probability of each event you are insured against – mathematical modelling!!!) How is climate change science any different?

  26. As one of the millions who sit close to the bottom of, “the credibility spectrum pyramid,” I’d like to know the name of the person who sits at the very top of it?
    Is it Hansen, Mann, Trenberth, Briffa, Jones or someone else?
    Is the top seat shared by any of those I’ve named?
    Where does the buck stop and who is ultimately responsible for any errors that may result from this most serious research that, depending on the final anaysis, should it ever be concluded, could affect all living creatures in some way?

  27. Joseph Seymour asked who sits at the very top of the credibility spectrum, and put forward some names. The answer is no one person or not even an elite group of persons sits at the top. There are some scientists (such as those named) whose opinion likely carries greater weight than others, but a good argument (as in a constructive dialogue debating points of fact and interpretation) by any other scientist can win the day. There are always young new scientists, and some old mavericks, making great breakthroughs who sometimes over-turn the existing paradigm.

    Science is a self-correcting system where decision making can be likened to how an ant colony works. No one is actually directing things, but there are sets of rules that govern behaviour (e.g., ethics, the scientific method, peer review to verify that the science described is factual and accurate). It is the net application of those rules that steer science away from big errors. To pick up the ant colony analogy, the ant that comes back with food from a new foraging area will be followed by at first a trickle of other ants, but if they in turn bring back food and other ants going to other places don’t, the tide will shift for awhile to the new foraging area. No one ant decided to redirect the ants.

    An example: Darwin’s ideas about evolution were not universally accepted by biologists or even geologists when he first published them, and the underlying genetic mechanism wasn’t properly explained until much later. As evidence accumulated in support of Darwin’s idea that natural selection was the principle underlying evolution, and that the earth was in fact very old and many transitional fossils were found, the theory became more complex and more robust. Climate change is no different. As we learn more about how the climate works, today and in the geological past, our understanding improves and the computer models are modified in different ways by different research teams to seek better predictions. The best models are then adopted, or the best changes incorporated into other team’s models.

    Science then is a trial and error system, rather than a directed ‘top down’ system where the minions lower down are instructed on what to do. Quite egalitarian, so in fact contrarians, scientists who hold ideas outside of the mainstream can prosper provided their ideas have some factual basis and use the scientific method (Scientific method: based on existing obervations pose an hypothesis; using new observations or experiments, test the predictions of that hypothesis; on the basis of the new data either reject the hypothesis or modify it to fit the better understanding, or accept that the initial hypothesis was right at which point it becomes a ‘theory’ or explanatory model).

  28. Unfortunately there is more to climate change than climate science.

    Let’s start by Googling “climate psychology”. I won’t attempt a diatribe on the subject because my background is engineering, but take a look at the first few dozen hits. Wouldn’t remaining in our nice warm beds as the Titanic sinks make more sense than risking our lives by jumping hundreds of feet into icy water? What will mass hysteria accomplish, anyway? If fixing climate means we have to give up our houses, cars, food, luxuries, and wealth, then why bother? What good is fixing climate if it destroys our lives, and we may not have to anyway, because science always comes through in time? Right?

    What about Googling “climate economics”? What do climate scientists know about this subject? Probably about as much as I do, which is virtually nothing. Check out the first few dozen hits. When the climate medicine is worse than the climate ailment, especially when the ailment may not harm me, then why bother? I may feel your climate pain, but I certainly will feel my climate medicine more than your pain. A Google search of “climate pain” will reveal that it is real. Anyway, “climate medicine” isn’t very popular, but “Climate Fix” tends to be a bit more trendy.

    Then there’s “climate mitigation” or “climate action”. Google brings up millions of hits on the second one. What do climate scientists know about these subjects? Who are the experts and what papers and websites are credible? Who decides? Climate scientists? Us?

    We could hone in on some of these broader subject areas. What about “climate fear” or “climate suicide” or “climate denial”? The consensus seems to be that climate denial is an organized attempt to disprove climate scientists, but I believe it is the result of human traits; when faced with overwhelming evidence of future disasters over which we have little or no control, our natural instinct will be ignorance (which can literally be translated into stupidity) or shoot the messenger if he persists. Otherwise perpetual fear and anxiety would drive us all crazy.

    What about Googling “climate happiness”? You’ll get fewer hits, but some people may be elated about the prospects of global warming. If you lived in a cold climate, you might welcome a few degrees extra warmth on those cold winter nights. One might also be enticed to read Climate, Affluence, and Culture (Culture and Psychology), which brings us full circle.

  29. There was some discussion about what effects increased levels of CO2 will have on plant growth. According to this article, If you think poison ivy’s bad, it could get worse, not all plants equally benefit from increased levels of CO2. Lazy vining plants like poison ivy and kudzu may benefit 18-20 times more from increased levels of CO2 than trees, because much more of their energy can go into producing leaves for photosynthesis instead of trunks and branches for support.

  30. IPCC hardly seems to belong at the top of the pile. The conclusions are watered down by a politicized (with hard pressure from somed national governments) consensus process, and much of the contents are outdated by the time the reports are published.

    Don’t get me wrong; IPCC provides some good background. But it should not be rated higher than other works. All need to be considered together.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.