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Strange Bedfellows

Filed under: — gavin @ 8 February 2005 - (Français)

Here’s a curious observation. Some commentators who for years have been vocally decrying the IPCC consensus are lining up to support the ‘Ruddiman’ hypothesis. A respected paleoceanographer, Bill Ruddiman has recently argued that humans have been altering the level of important greenhouse gases since the dawn of agriculture (5 to 8000 years ago), and in so doing have prevented a new ice age from establishing itself. This intriguing idea is laid out in a couple of recent papers (Ruddiman, 2003; Ruddiman et al, 2005) and has received a fair degree of media attention (e.g. here, and here).


The basic idea mainly relies on paleoclimatic evidence that there would have been a new ice age by now under ‘normal’ circumstances, and since there isn’t one, anthropogenic influences are presumably to blame. Whether this is valid or not is now the topic of some debate at scientific conferences. One can argue about the details (and I have here for instance), but the relevant issues are quite technical and not really what I want to talk about. Instead, I will explore what acceptance of this idea implies.

The attraction to this idea for the contrarians is not hard to see. They have seen quickly that this is a controversial and non-mainstream idea (and even Bill Ruddiman will allow that!), and that Ruddiman appears to be ‘battling’ against the science establishment. So, following a sort of ‘the enemy of my enemy is my friend’ logic, they have been vocal in supporting Ruddiman’s ideas (I should hasten to add that this support does not reflect on the quality of Ruddiman as a scientist, nor on the validity of his thesis).

For instance, take this quote from TCS

Given Ruddiman’s findings the key question now is not “is industrial-age, human-caused global warming occurring?”, but rather “are we sure that the human effect on climate over the last 8,000 years has helped to prevent the occurrence of another glaciation?” Should the answer to that question be yes, then it prompts the further question: “do we wish to maintain the human warming effect, or instead to counteract it and allow Earth’s climatic cycle to drop back into its next (natural) glacial episode?”.

Or from the Idso’s site:

Hence, even if the IPCC is correct in their analysis of climate sensitivity and we are wrong in suggesting the sensitivity they calculate is way too large, the bottom line for the preservation of civilization and much of the biosphere is that governments ought not interfere with the normal progression of fossil fuel usage, for without more CO2 in the atmosphere, we could shortly resume the downward spiral to full-fledged ice-age conditions.

There are multiple strands of intellectual incoherence here. Firstly, people who have argued that there really hasn’t been a significant rise in CO2 since the 1800s, now accept the ice core results that show there was a much smaller rise from 8000 yrs ago. Secondly, those that argued that the 20th Century CO2 rise cannot be anthropogenic, appear to accept that the post-8000 BP change was. Thirdly, those who argue that the current increase in greenhouse gases has no significant climate effect, now appear to believe that the much smaller changes in the pre-industrial prevented an ice age.

This is like someone who believes the earth is flat buying a round-the-world ticket for their vacation.

Let me make it a little clearer. If one accepts Ruddiman’s hypothesis, one implicitly agrees that: i) CO2 and CH4 can be affected by human activity, ii) greenhouse gases have a significant forcing role, and iii) climate sensitivity is in the ballpark of mainstream estimates. (The opposite is not however true, one can agree on those three points (which is pretty much the IPCC consensus) without necessarily thinking that Ruddiman is correct). One must therefore conclude that those contrarians who have warmly welcomed Ruddiman’s thesis have now come around to mainstream opinion. Hmm…

But wait, they might say, we don’t believe any of those things, but we accept that we may be wrong, in which case, Ruddiman’s theory still implies that we should not do anything about increasing CO2 . No. At minimum it might indicate that reducing CO2 below pre-industrial levels might not be a good idea, but that is far from saying that any amount of further increases are beneficial. It certainly doesn’t follow that if a little bit of CO2 is good for the climate, then a lot more is better.

I think a more obvious explanation is that, for some critics, any argument will do – regardless of its coherence with the argument they had before, or the one they will pick next.


60 Responses to “Strange Bedfellows”

  1. 51

    While obviously true that very few studies are actually replicated, the more valid rubric is their reproducibility as judged by peer review.

    Scientific resources are limited. The most important results are being reproduced/replicated over and over — witness the “hockey stick” genre of reconstructions of global temperature over the past millenium. But the vast majority of scientific studies fall in the category of “obviously reproducible” and/or “highly specialized and narrowly focused” — so science finds its resources better spent elsewhere.

    Political debates centered around scientific topics tend to have fairly short shelf lives, dissipating or morphing as new science emerges. As one person, with a finite attention span and energy, I’ve made some choices about how to most usefully devote my time. What matters to me is the search for clues as to which bits of the science knowledge gleaned during our time will remain valid and useful a century or more from now.

  2. 52
    Grundt says:

    Maybe all of you, the last 10 or 20 or more posters, are right..
    Prof. Wetzel, you are right, but, then, almost no one is making real Science..

    For example, in Catalysis (Science), you might never reproduce an absolutely well designed experiment, no matter how well you think you are planning it.

    Once happened -(maybe thousand times different things happen this way)-,
    that a group of chemists obtained an extraordinary compound or result, I´ll call it the X experiment..

    Never more they could reproduce it, despite all the care and dedication, effort, money, etc.

    After months of countless experiments, it was noticed I don´t know how, that the flask in which the X Homogeneous Catalysis experiment was done, a molecular intrusion or wathever, so small that, obviously, you could only notice by elecron microscopy, was the factor that allowed such a very interesting and extremely important result.

    So, Science is sometimes a black box, unless for some experiments scientists can have information about even every atom involved. Not easy.

    That´s why it is so difficult to draw conclusions easily from models, appearance, etc.

    Climate? A very difficult monster to understand, it seems.

  3. 53
    Dan Allan says:

    Hmm… thought we were supposed to be discussing Ruddiman in this section. But allow me to jump in. I agree in large measure with Peter Wetzel (though I have sparred with him previously), but would add a few thoughts:

    It is really counter-productive to question the motives of scientists based on who funds them, where they speak, who they are friends with, etc. The fact that one’s scientific views and one’s political are aligned does not mean that one’s political views precede and drive one’s scientific views. Nearly everybody believes that their scientific views are borne of the evidence, that they are *right*, and practicing objective science.

    I would draw an analogy to another field that demands objectivity by look at “Bush versus Gore”: Probably every Supreme Court justice believed that his or her decision was basely purely on objective legal reasoning. Yet what a funny coincidence that the conclusion each justice reached matched exactly his or her political leaning!

    In the end, questioning motives implies that we understand this very complicated concept of *motive*. No doubt some scientists are persuading themselves of their scientific views, consciously or subconsciously, or unconsciously, in order to align them with political views – just as the Supreme Court justices did. But to what extent does this unconscious or semi-conscious self-deception mean someone’s motives are tainted?

    Motives are multi-faceted, unknowable and immaterial. If Lindzen is mistaken, he will ultimately be refuted with evidence and science – not with aspersions because he spoke at the evil Cato Institute.

    Second point: there is a natural tendency among humans, and especially humans who become scientists, to want to be right. Thus, once a side is taken in a debate, many of us tend to dig in our heels deeper and deeper, try harder and harder to prove our points. As evidence supporting our view grows weaker, it only makes us more desperate and therefore more emphatic. This is especially amplified in a public, scientific debate. The wish to have be right, and the even more fundamental wish not to suffer the perceived public humiliation of being wrong, causes many scientists to quickly lose their objectivity and deceive themselves regarding their motives and beliefs. It would serve the scientific community well to recognize this, take a rhetorical step back, and go out of one’s way to be receptive to – or at least courteous in responding to – opposing views.

    One area I might disagree slightly with Wetzel: he says that ultimately, “the truth will out.” Maybe so. But it seems to me we are still debating evolution, at least in public and political spheres. I wish the truth would out already! I suppose “the truth will out” in the scientific community. Not so optimistic about the rest of society.

    – Dan

  4. 54
    Joseph O'Sullivan says:

    The climate science debate has two aspects that unfortunately can’t be separated.

    There is the pure science part. RealClimate is great on this. I was interested in the concept of thresholds and the discussion (Moberg et al post started Feb. 15) was very illuminating including the comments by Peter Wetzel. I may digress, but the potential effects of climate change on coral reefs are something I am also interested in. That is one of the reasons I put in the link to the study of ocean warming at Scripps in an earlier comment. Coral reefs are among the most diverse and complex ecosystems on the planet. They are also very sensitive to abiotic environmental conditions, like temperature. Recent el nino events that warmed the tropical Pacific Ocean caused large scale, but temporary, coral die-offs. Will climate change cause large scale coral die-offs? As far as I know this this is a real possibility but it’s still pretty speculative. This is a purely scientific question: what does current science say about the potential effects of climate change on coral reefs?

    Politics is the other part of climate change science. When science goes public, out in the wide world as William says, it gets political. Climate change science is a prime example of this. On RealClimate, in my opinion, political aspects should be occasionally brought up but should definitely be a sideline to the science. A path needs to be cut through the political jungle so the accurate science can come out. Thanks to Michael Tobis for the comment that supported me. I think RealClimate has also done a good job on the political side too. A short statement or two on the politics while allowing political discussion without getting involved is the best course of action.
    Analogous to climate change science is the politics of evolution science. Thanks to Dan Allen for bringing this up. Polls have shown that about half the people in the U.S. do not believe in evolution, and President Bush has said “the verdict isn’t in” on evolution. As a biologist I almost gag when I hear this. I knew evolution is a proven scientific fact, but out of curiosity I read Darwin’s “Origin of Species” a few years ago. This book showed overwhelming evidence for evolution nearly 150 years ago, but people still don’t accept it as fact today. In the public mind evolution is not a matter of scientific fact but more as a philosophy that is a matter of opinion and personal choice.

    Now I will go back to the politics of climate change science (I’m sorry I just can’t help it). Senator Inhofe, by calling climate change science an “article of religious faith”, wants climate change science to be seen as a matter of opinion or personal choice and an extreme one at that, but not as scientific fact. This is again about stopping action on climate change laws and regulations. To put it glibly the position is: “If it’s not a fact you must not act!”

    Everyone is entitled to their own opinion but not their own facts. Everyone needs to hear the facts. RealClimate can and does help people get the facts of climate change science.

  5. 55
    Grundt says:

    Excellent discussion, all of you are real Scientists.
    A pity I cannot express as I would like in English (I can do it only in Spanish)
    It is very fortunate realclimate.org exists.

    It is hard to hear ” ..President Bush has said “the verdict isn’t in” on evolution..”, and all this nonsense about “climate change an article of religous faith”!!

    Well, I feel we are still in the Caves Era…..depressed today..
    We are having disaster after disaster with climate and lack of prevention and lack of common sense here in Venezuela, and all around the world… I have not great hopes for the Future.

    But we will keep trying to understand what to do. Until the end.

  6. 56

    I thought “articles of religious faith” were beyond reproach, handed down from an omnipotent deity, requiring and demanding action on penalty of eternal damnation. Perhaps the senator should think twice about elevating climate science to such a lofty pedestal. (wry smile)

    That’s about as close as I’m going to go to playing the political rhetoric game.

    Religion can be scientifically proven to be an important factor in the course of human affairs. Humans act (often to great effect) on all manner of beliefs that are simple to refute scientifically.

    Greed and self-interest play an equally important role in human dealings. Acting on no belief whatsoever, but simply for individual gratification, monarchs and dictators have shaped the affairs of men arguably more than democratic processes have.

    The balance of forces which defines human nature and human motivation arguably only has room for so much science. And balance is a good thing. A world driven entirely by science would be unbearably stifling.

    The balance on this site is defined by the lead paragraph which appears on the upper right of every page we read here. In practice, “commentary” necessarily involves a dabbling in politics. So I do fully subscribe to Joseph O’Sullivan’s moderate view: “On RealClimate, in my opinion, political aspects should be occasionally brought up but should definitely be a sideline to the science.”

    On the issue of coral bleaching, I wonder how much is known from proxies about how often this phenomenon occurred in the past. And how did coral ecosystems tolerate the much warmer climates of 50+ million years ago?

    [Response - Good question. Basically the loss of the symbionts by the corals (=bleaching) does not leave any track behind, although maybe altering the geochemistry of the corals (through the loss of photosynthetic activity). The other problem is that during the last 50 million years, both symbionts and scleractinians evolved. Because the long term trend of the last 50 or so million years was toward a cooling, the modern corals and symbionts seem to be better adapted to cool temperatures than warm ones – see for example the paper by Tchernov et al. in PNAS . So even if we had some good ideas of how did the corals were reacting to warmer early Cenozoic temperatures, the difference of coral and symbiotic communities would make it tricky to apply to modern changes. (Browsing the references databases, I did not find anything on the coral reefs during the Paleocene thermal maximum, which could be useful.) -thibault]

  7. 57
    Joseph O'Sullivan says:

    How coral ecosystems handled warmer climates in the past is a good question. I’m not sure. I have not been active in the field for several years and I consider myself to be a well-informed but amateur naturalist.

    If I remember right most of the modern coral species are the result of an evolutionary expansion that occurred after the warmer climates about 50+ million years ago.
    I know in general ecosystems shift geographically in response to climate change. Coral reefs require a narrow range of environmental conditions e.g. water depth, temperature, salinity, clarity and nutrient level, so their ability to shift is limited. Another related question would be the rates of past climate change. Coral ecosystems react slowly to change and a rapid temperature change would be harder to handle.

    At present corals are effected by a range of man-made activities like coastal construction, pollution, fishing and possibly introduced diseases. In the Caribbean some coral bleaching has been caused by pathogens not native to the Caribbean and are more common in terrestrial ecosystems. Climate change adds another level of complexity to these issues.

    A science comment without politics, I am proud of myself!

  8. 58
    Richard Harvey says:

    Gavin, I have not read all the posts so forgive me if my question is a repeat from an earlier post.

    The question that concerns me and that has not been addressed in the posts I’ve read so far is that Ruddiman has not provided estimates of the required land-use change and GHG emissions that would back the plausibility of his hypothesis in a *quantitative* manner. Granted forcings of 40ppm CO2 and 250ppb CH4 should lead to DEL(T)=0.8C globally given a climate sensitivity of 2.5-3C for 2XCO2 (see post #5 above), but are those forcings even plausibly attainable through human intervention with pre-historic technology? Could, say, a few tens to hundreds of millions of people back then have added almost half of today’s CO2 emissions, this time due to billions of people?

    And even if we admit to this hypothesis, there remains puzzling questions. For example, the methane “anomaly” shown to rise above the “normal” downward trend 8000 yrs ago resembles a similar departure from orbital forcing about 230 Kyrs ago (Ruddiman, 2003; Fig. 1). In addition the latter has about the same magnitude as the more contemporary one, but it occurs at a later phase, when the orbital forcing it lower than today’s. Why isn’t he also looking at explaining this departure? And why doesn’t he start by carefully ruling out mechanisms in natural methane cycle changes before even thinking about a human-induced change? He focuses too much on orbital forcing while minimizing the role of possible (and complex) feedbacks between methane and the rest of the climate system. Millenial-centenial climate variability is *not* only caused by orbital forcing!

    To be sure, his statistical correlations are interesting and worthwhile to investigate, but his hypothesis is largely based on circumstancial evidence that still keeps him on shaky grounds. All the hoopla he shows in his recent papers are premature.

    Am I being too critical?

    [Response: Well, you aren’t alone in being sceptical of the details and the points you raise are good ones. These are being addressed in the literature, but I think the most tactful statement is that the jury is still deliberating… – gavin]

  9. 59
    Joseph O'Sullivan says:

    Anyone interested in the potential effects of climate change on coral reefs can look up a new publication released by the Pew Center, “Coral Reefs & Global Climate Change” a summary of the current science on this issue at:
    http://www.pewclimate.org/press_room/sub_press_room/february13.cfm
    The Pew Center is not an environmental group like Sierra Club, Environmental Defense and the NRDC. Pew is a non-partisan philanthropic foundation focusing on education and is similar to the Carnegie and Rockefeller foundations. The Pew Ocean Commission, made up of republican and democratic politicians, environmental groups, commercial fishermen and scientists, released a report on the state of the oceans that is highly respected.
    The commentator mentioned at the start of this post, the Greening Earth Society (a fossil fuel company funded advocacy group that emphasizes in their words “the scientifically sound” perspective on CO2 and global climate change), has misrepresented the science on coral reefs and climate change. It cites three studies that show that some corals have demonstrated some resilience to warming, and then extrapolates that there is no need to be concerned about climate change’s effects on coral reefs. This is another case of twisting science. Some resilience is not the same as complete or even substantial resilience.

  10. 60
    Stewart Longman says:

    As has been pointed out many times above, there are skeptics, and there are those who appropriate the label skeptic. In history or biology (think evolution), we would call them deniers. Is the science at a point now where it is irrefutable? Some people will still deny the reality of climate change as some deny evolution, or the Holocaust,, while scientists will still work on the details, models, etc., just as evolutionary biologists and hisotrians are still hard at work. No one asks a university (or news program) to represent diversity by appointing creationist biologists and denying historians, and Flat Earh Society members are not invited to give their opinion about the International Space Station. If the time is right, and the science is firm enough, then it’s time to call these people, who are advancing a definite agenda (‘Burn More’) what they are: climate change deniers, nothing skeptical about it.


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