Anthropogenic Warming Is Part of the ‘Hard Core’ of Climate Science

Mike Thicke

The party line of climate change skeptics these days is that global warming has paused, or even reversed, in the last 15 years. According to the Nongovernmental Panel on Climate Change, “Global temperatures stopped rising 15 years ago despite rising levels of carbon dioxide, the invisible gas the IPCC claims is responsible for causing global warming.” Typical denialist refusal to accept the facts, right? Perhaps not! A recent paper in Geophysical Research Letters explains, “Although the Mount Pinatubo eruption in 1991 caused a short-term reduction in TOA radiation, increasing greenhouse gases should have led to increasing warming. However, sea surface temperature (SST) increases stalled in the 2000s and this is also reflected in upper ocean heat content (OHC) for the top 700 m in several analyses.”1 Despite this apparent anomaly, however, climate scientists have not been jumping ship from their consensus position that anthropogenic global warming is occurring.

Diagram of apparent 'missing heat'. Courtesy Science, via https://www2.ucar.edu/atmosnews/news/2013/missing-heat-may-affect-future-climate-change

Diagram of apparent ‘missing heat’. Courtesy Science, via https://www2.ucar.edu/atmosnews/news/2013/missing-heat-may-affect-future-climate-change

Skeptics see this lack of response as evidence of liberal bias or even conspiracy, but I think there is a much more compelling explanation: anthropogenic warming is part of the hard core of climate science. That is, the AGW claim is not subject to revision, and so when anomalies occur—when observations fail to meet predictions—other components of climate science must be revised to preserve it.

“Hard core” is a term from philosopher of science Imre Lakatos’s account of scientific change. According to Lakatos, scientific research programs consist of a hard core of propositions that are not subject to revision surrounded by a “protective belt” of propositions that are subject to revision. These revisable propositions are also known as “auxiliary hypotheses”. When observations conflict with the research program’s predictions, it is the auxiliary hypotheses that are altered in response. In Lakatos’s account, research programs are judged “progressive” if alterations to the auxiliary hypotheses generate novel predictions and “degenerative” if they are not. Research programs that are continually degenerative ought to be, he claims, abandoned.

Faced with temperature readings that did not match model predictions, climate scientists did not abandon the AGW proposition, because it is part of climate science’s hard core. Rather, they searched for where the “missing energy” might have gone. Recently, two papers have offered possible solutions. First, the above-quoted paper from Balmaseda, Trenberth, and Kälén argues that this missing energy has been located in the deep ocean, below 700 m. Based on model reanalysis and measurements, they conclude that there is “a long-term ocean warming trend, while heating continues during the recent upper-ocean-warming hiatus, but the heat is absorbed in the deeper ocean. In the last decade, about 30% of the warming has occurred below 700 m, contributing significantly to an acceleration of the warming trend” (1754). Starting around 1998, they tell us, changes in wind patterns have caused stirring of the ocean in a way previously unaccounted for by climate models. It is this part of the climate science research program—propositions concerning deep ocean circulation—that should be revised.

Second, a forthcoming article by climate scientists Kevin Cowtan and Robert G. Way concludes that the missing heat is not missing at all, but is instead underestimated by surface measurement networks. They report, “Microwave sounding data from satellites, reanalysis data from weather models, and observations from isolated weather stations all confirm that the unobserved regions of the planet, and in particular the Arctic, have been warming faster than the globe as a whole since the late 1990s.”2 It is no simple task to measure global temperatures, partly because not all parts of the planet are equally covered by measuring stations. Cowtan and Way argue that there is a correlation between poorly-covered locations, such as the Arctic, and locations where there has been significant surface heating. Therefore, surface temperatures have been rising all along; our measurements have just failed to record this warming.

Because it was not an option for climate scientists to revise their belief that anthropogenic global warming is occurring, they were forced to search for other explanations for the apparent failure of climate model predictions to match observations over the last decade. Such explanations have now been found. Skeptics see these recent reports as ad hoc attempts to preserve an untenable hypothesis, but the work of Lakatos councils us to judge them differently: as corroborated novel predictions resulting from the alteration of auxiliary hypotheses. It is conceivable that, in the future, the current consensus climate science research program will degenerate and need to be abandoned, but there is no sign of that yet. This is just science as usual.

 

  1. Magdalena A. Balmaseda, Keven E. Trenberth, and Erland Kälén, “Distinctive climate signals in reanalysis of global ocean heat content,” Geophysical Research Letters, Vol. 40 (2013), 1754.
  2. Cowtan, Kevin, and Robert G Way. 2013. “Coverage Bias in the HadCRUT4 Temperature Series and Its Impact on Recent Temperature Trends.” Quarterly Journal of the Royal Meteorological Society (November).
Mike Thicke

About Mike Thicke

Mike is a Ph. D. candidate at the University of Toronto's IHPST. His research concentrates on social epistemology, the use of economics in philosophy of science, and philosophy of economics.

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17 Responses to Anthropogenic Warming Is Part of the ‘Hard Core’ of Climate Science

  1. Boaz Miller Boaz Miller says:
    [+]

    A few comments: 1. Why is Cowtan and Way's claim a novel prediction rather than an ad hoc explanation? 2. The fact that a research program is progressive is a reason for scientist to pursue it (and it is also rational to pursue a degenerative research program, as long as you are aware it is degen...

    • Greg says:
      [+]

      1. They aren't novel predictions. But Lakatos doesn't demand that the auxiliary changes provide novel predictions in the same context which forced the auxiliary revisions (that would be too stringent). Novel predictions in other contexts, using the improved surface observation network, would be suff...

      • Mike Thicke Mike Thicke says:
        [+]

        I think they could be considered novel predictions. In the first case, the 'novel prediction' is that the deep ocean has been heated. The scientists then go looking to see whether the deep ocean has heated, and find that it has. In the second case, the 'novel prediction' is that heating is concentra...

    • Mike Thicke Mike Thicke says:
      [+]

      (1) I believe Lakatos would judge these additions to climate science based on whether they generate further novel predictions. (2) I'm a bit of an anarchist with respect to theories of science. I think Lakatos is a good emendation upon Kuhn, and I think they both capture interesting aspects of h...

    • Mike Thicke Mike Thicke says:
      [+]

      For what it's worth, Philosopher's Index shows a fair number of Lakatos references post-2000. Most of them are better classified as history of philosophy, but there are still some treating Lakatos as a live option. Eg. Zenker, Frank "Lakatos's Challenge? Auxiliary Hypotheses and Non-Monotonous Infer...

  2. Jason says:
    [+]

    Been a while, Mike. But I noticed the post on GW through Facebook, so thought I'd throw in my two cents. What exactly do you mean when you say AGW might not be subject to revision. AGW is just the two-part claim that (a) humans are changing the composition of the atmosphere, and (b) there is a ...

    • Mike Thicke Mike Thicke says:
      [+]

      Thanks Jason--- Scientists don't just arbitrarily decide that something isn't up for revision. Revising the AGW hypothesis would have, as you say, major implications for atmospheric physics. Climate scientists would also have to puzzle over satellite data suggesting that there is a flux imbalance...

  3. Iain says:
    [+]

    Of course, the most common response to this denialist claim is simply to point out that it is false. The "pause" is only a pause if you take the outlier year 1998 as on trend. But since temperatures fluctuate above and below the mean all the time, this is silly. If you look at any reasonably constru...

    • Mike Thicke Mike Thicke says:
      [-]

      “Reasonably constructed trend lines” is in the eye of the beholder. Look at this graph: http://img.skitch.com/20100221-prdfcnkdqdtf6dkg1p4q162mea.gif and tell me that the only reasonable trendline is upwards. If warming really did pause starting in 1998, how would you know?

      • Iain says:
        [+]

        Mike, as I'm sure you know, there are standard statistical methods for drawing trend lines - though there is some subjectivity in the choice of method, it is not just in the eye of the beholder. The most obvious way of smoothing out annual variability to get at long term trends is to use moving aver...

        • Mike Thicke Mike Thicke says:
          [+]

          Of course you can use moving averages, and that is what the IPCC reports do (generally 5-year moving averages). But skeptics could (quite fairly I think) reply that a moving average will tend to disguise short- to medium- term changes. There is a theoretical assumption behind a moving average: that ...

  4. Iain says:
    [+]

    The gif uses simple regression to get straight lines, not moving averages. The point is to show that you get absurd results if you cherry pick the start and end years of your data series. It's not that the lines all have a different slope, its that they are radically discontinuous when you try to f...

    • Mike Thicke Mike Thicke says:
      [+]

      The last image in the GIF is a single straight line, that is what I was referring to. The whole point of those articles is that there *is* an anomaly to be explained! (Edit: And so arguments that the "pause" claimed by skeptics is merely the result of statistical cherry-picking aren't tenable, be...

    • Mike Thicke Mike Thicke says:
      [-]

      Of course if you look at skeptical arguments as a whole, they are extremely ad hoc, selective, and deceptive. It just happens that in this case they happened to be somewhat close to the truth.

  5. Boaz Miller Boaz Miller says:
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    The problem may be with "novel predictions" as a concept, but these don;t sound like novel predictions. This has the structure of an ad hoc codification: "we should expect X. We don't observe X. Why? Maybe Y. Yes, Y". If indeed the anthropogenic global warming hypothesis is part of the hard core, ...

    • Mike Thicke Mike Thicke says:
      [+]

      Thinking about your previous comment I came across this paper today: Hunt, J Christopher. 2012. “On Ad Hoc Hypotheses*.” Philosophy of Science 79 (1) (January): 1–14. doi:10.1086/663238 (http://www.jstor.org/stable/info/10.1086/663238). In this article I review attempts to define the term ...

  6. Pingback: Prediction Models for Science: Preliminary Review and Thoughts | The Bubble Chamber

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