A sober view of ‘climate change’, by someone who actually works in the field

The United States Senate Committee on Environment and Public Works held a hearing on 18 July at which a number of leading climate scientists gave testimony. One of them was Roy Spencer, who is best known for his work on satellite measurements of climate phenomena. He is a calm and unfussed scientist who rarely raises his voice, but just gets on and done his work. What he said in his presentation was most interesting.

Dr Spencer is no slouch in this field, where he has been working for nearly thirty years. He was a NASA scientist, with a Medal for Exceptional Scientific Achievement to show for it, and he has published lots of papers, on global temperature monitoring with satellites, on the amount of warming we might expect from greenhouse gas emissions, how to monitor hurricane strength from satellites, and quantitatively explaining ocean heat content changes. For some years now he has been a principal research scientist at the University of Alabama at Huntsville.

‘My overall view of the influence of humans on climate is that we probably are having some influence, but it is impossible to know with any level of certainty how much influence. The difficulty in determining the human influence on climate arises from several sources: (1) weather and climate vary naturally, and by amounts that are not currently being exceeded; (2) global warming theory is just that – based upon theory; and (3) there is no unique fingerprint of human caused global warming.

My belief that some portion of recent warming is due to humans is based upon my faith in at least some portion of the theory: that the human contribution to atmospheric greenhouse gas concentrations has resulted in an estimated 1% reduction in the Earth’s ability to cool to outer space, and so some level of warming can be expected to occur from that change.

Exactly how much warming will occur, however, depends upon something we call “climate sensitivity” (Spencer & Braswell, 2010; 2011), and relatively few researchers in the world – probably not much more than a dozen – have researched how sensitive today’s climate system is, based upon actual measurements. This is why popular surveys of climate scientists and their beliefs regarding global warming have little meaning: very few of them have actually worked on the details involved in determining exactly how much warming might result from anthropogenic greenhouse gas emissions.

Our most recent peer-reviewed paper on this subject, Spencer & Braswell (2013), has arrived at a climate sensitivity of only 1.3 deg. C for a doubling of atmospheric carbon dioxide, based upon a variety of global measurements, including warming of the global oceans since the 1950s. This level of warming is below the lower limit of 1.5 deg. C minimum predicted in the last (AR4) IPCC report. It is also in line with (an admitted minority of) other estimates of low climate sensitivity published in the peer review literature.

It should also be noted that the fact that I believe at least some of recent warming is human-caused places me in the 97% of researchers recently claimed to support the global warming consensus (actually, it’s 97% of the published papers, Cook et al., 2013). The 97% statement is therefore rather innocuous, since it probably includes all of the global warming “skeptics” I know of who are actively working in the field. Skeptics generally are skeptical of the view that recent warming is all human-caused, and/or that it is of a sufficient magnitude to warrant immediate action given the cost of energy policies to the poor. They do not claim humans have no impact on climate whatsoever…’

Ho goes on to discuss two of the currently popular topics in AGW.

‘The lack of statistically significant warming in the last 15 years … is sometimes glossed over with the claim that the global temperature record has a number of examples of no warming (or even cooling) over fifteen year periods. But this claim is disingenuous, because the IPCC-presumed radiative forcing of the climate system from increasing CO2 has been at its supposed maximum value only in the last 15 years. In other words, when the climate “stove” has been turned up the most (the last 15 years) is also when you least expect a lack of warming.

It is time for scientists to entertain the possibility that there is something wrong with the assumptions built into their climate models…’

‘The claim has been made that the extra energy from global warming has mostly bypassed the atmosphere and has been sequestered in the deep ocean, and there is some observational evidence supporting this view (e.g. Levitus et al., 2012). But when we examine the actual, rather weak level of warming (measured in hundredths of a degree C) at depths of many hundreds of meters, it implies relatively low climate sensitivity (Spencer & Braswell, 2013)… ‘

Even if our ocean temperature measurements of deep warming of hundredths of a degree over the last 50 years are correct, and mostly due to human greenhouse gas emissions, they probably do not support the IPCC’s pessimistic view of future warming.’

There’s much more in this patient statement that repays reading. I liked the cool reference to the Cook et al. monstrosity of a paper that I wrote despairingly about when it was published. How can peer review let through something as bad as this?

 

 

Join the discussion 16 Comments

  • dlb says:

    There is a chap who goes by the name “pokerguy” on many bloggs who wants sceptics to put this 97% nonsense to bed. He wants a proper peer reviewed survey on what scientists really think of this AGW theory. So far the response to his idea has been rather lacklustre. He feels so strongly that he is willing to finance some of the cost of such a study.

    • Peter Kemmis says:

      Hi dlb

      Would you care to craft a questionnaire that could be put to scientists? Obviously the Cook questionnaire was extraordinarily simplistic, and I’m also no doubt among that 97%. (Except the fact that I have no claim to being a scientist, although somewhere in my distant past when working in the U.S. on software, someone wanted to boot me upstairs, or rather sideways, and hoped I might be mollified with the title of “Chief Scientist”! What a scream that was.)

      Perhaps we could offer some comments on a draft, and then test it initially, before taking this idea further with “pokerguy”. What do you think?

  • Peter Gummer says:

    I was puzzled by Dr Spencer saying, “The difficulty in determining the human influence on climate arises from several sources: … (2) global warming theory is just that – based upon theory”. This seems to be self-contradictory. As Dr Spencer accepts that global warming has the status of a theory, this would support strongly the proposition of human influence rather than diminish it. A theory is as good as you get in science: plate tectonics and relativity are called “theories” rather than “hypotheses” or “vague hunches”. So I really don’t get Dr Spencer’s point: was he actually trying to suggest that global warming is just a hypothesis?

    • dlb says:

      Peter, Spencer was testifying before senators who probably don’t know the difference between a theory or a hypothesis. For the average lay person theory means something theoretical, an idea yet to be proved by experiment or observation. You bring up plate tectonics, well how about “string theory” a hotly contested hypothesis in physics?
      AGW is definitely theoretical with increasingly little empirical evidence to support it. Arguing about hypotheses and theories is just semantics.

      • Peter Gummer says:

        I’m not arguing about anything, dlb, just trying to understand what Dr Spencer meant since his point (2) didn’t make sense. In science, the difference between a hypothesis and a theory is definitely not “just semantics”.

  • Don Aitkin says:

    I think Peter is right — he meant that it was just a hypothesis without much support from observations. And I think dlb is also right, in that Spencer’s somewhat sloppy use of words reflected the audience he was speaking to.

  • dlb says:

    In reply to Peter Kremis.

    Hi Peter,
    Here is the sort of questionnaire I would like to see. No idea how you would circulate it around the scientific population and secure it to stop bogus voting?

    I think it would need to have a preamble as I assume many scientists outside the climate field would only have heard of MSM reports on climate change. What I mentioned about clouds and the models is not definitive and would need to be checked. Perhaps it could also be mentioned that some recent modelling is showing lower climate sensitivities but I don’t know how valid this is?

    The preamble would state the following facts:
    · The direct greenhouse effect from a doubling of CO2 is a global temperature rise of approximately 1deg C.

    · Modelling considered by the IPCC in 2007 states the likely rise of temperature from a doubling of CO2 would be in the range 2 – 4.5C. This modelling assumes positive feedback from water vapour.

    · Critics of the above estimate say that any temperature forcing is probably moderated by negative environmental feedbacks. Such feedback mechanisms are largely hypothetical but clouds are a prime candidate. With considerable uncertainty about the effect of clouds on climate this would throw doubt on the IPCC modelling.

    · The pre industrial concentration of CO2 in the atmosphere is estimated to be 280ppm and has increased to 400ppm through the burning of fossil fuels. It is currently increasing at 2ppm a year so at this rate would double around 2213.

    · Global temperatures have increased by 0.8C since the 1880s though they have not risen in the past 15 to 17 years, despite increasing CO2 concentrations.

    · Some researchers claim the temperature hiatus may be due to shading from aerosol pollution, there is also evidence of increasing ocean temperatures below 700m which some consider may account for the missing heat.

    Then the primary question would be:

    Neglecting any natural influences such as the sun, volcanoes or oceanic cycles that may affect temperature, given a doubling of CO 2 would you consider the average global temperature to rise by:

    a/ (nothing), CO2 will have no effect
    b/ 0-2C (minimal to modest) rise due to negative feedbacks in the climate system
    c/ >2C (an appreciable amount) of warming due to positive feedbacks
    d/ Not prepared to say as the science would appear to have many uncertainties.
    e/ I’m sorry I really don’t know enough to make an informed decision.

    Then perhaps two other question to see what field they work in and their qualifications

    • Peter Kemmis says:

      Thanks dlb

      I like your use of a preamble. Using its style, could the list be structured along the lines of:
      a) main issues agreed by both sides
      b) major contentions by the IPCC over which there is significant disagreement
      c) contrary contentions by those disagreeing with (b) above ?

      In “Taxing Air”, Bob Carter et al lay out such a structure, which I recall Don Aitkin referencing in an earlier post.

      Respondents could be asked to rate each issue of (b) and (c) using the typical 5 point scale ranging from “strongly agree” to “strongly disagree”.

      Could such a questionnaire also ask whether respondents had changed their views about AGW over time, and if so, over what period? The replies on this could be interesting because they may indicate some trends occurring as more information and observations become available.

      As for circulating such a questionnaire as well as avoiding bogus responses, I look to others for suggestions. The only idea I have at the moment is to put it out to cyberspace with the suggestion that this is the kind of more thoughtful questionnaire that is asking meaningful questions. Doing so may also be of value, just for people to think about.

      • dlb says:

        Thanks Peter,
        and apologies for getting your name wrong.
        Yes, I certainly agree with the structure of the preamble you give. One would certainly need to be neutral not pushing either the orthodox or sceptic view.
        With the 5 point questions I always think you need a “Don’t know” or something similiar. When I don’t know I am always forced to tick the middle box which which normally indicates “neutral” which is not how I feel.
        Agree, a question on whether respondents have changed their mind would be interesting.
        Regards

        • Peter Kemmis says:

          Hi dlb

          I have usually taken the middle box “neither agree nor disagree” as including “don’t know”. Perhaps experts in such surveys can advise.

          Don asks how the survey might be circulated. As I doubt John Cook would be interested, having released the results of such a delightful one recently, why don’t we call on Jo Nova or Anthony Watts to host it? Of course, the problem may well be that the respondents may largely be drawn from a sceptically-skewed portion of the scientific population. It seems pertinent that in addition to determining their qualifications and current fields of work, questions are included that elicit any changes in their views over time.

          So for example, if 100% of respondents stated they had always held the views expressed in their answers, and all those answers were strongly sceptical, we would conclude the survey targeted “permanent” sceptics only. However, if 50% replied that they had changed their views from being pro-CAGW to sceptical (and/or vice-versa), we have a different and more informative result. Trends are often useful, and sometimes can be reasonably extrapolated, but I’d want some informed advice on that.

          To limit bogus responses, could we not ask at least for email addresses and automate a confirmation email? This should limit duplicate bogus (and valid) replies, but otherwise with a survey of anonymous responses I don’t see how we can avoid the risk entirely.

          The other matter is of course that any meaningful results are issued with care and qualification, so they can’t be confused of pretending to be what they are not.

  • Don Aitkin says:

    dlb — the third dot-point in your preamble worries me a little, because you get into argument rather than facts. Why not simply say that both positive and negative feedbacks are hypothetical because the influence of clouds has not yet been demonstrated — or something like that?

    Otherwise, it seems a good one. Now, how to get it to the respondents?

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