The doctor’s analogy: people defer to the expert consensus of climate scientists

Another term that I recently learned is “False Equivalence” (when two things are proposed as being equal, although there are substantial differences between the two). Reading the Skeptical Science article “97% consensus on global warming” that I discussed in previous posts, I spotted one right away. It is the good ol’ doctor’s analogy.

This is how it is explained in the article:

Expert consensus is a powerful thing. People know we don’t have the time or capacity to learn about everything, and so we frequently defer to the conclusions of experts. It’s why we visit doctors when we’re ill.

Which is all true. Expert consensus is indeed a powerful thing. It is also true that people are not able to learn about everything and, in things we don’t know much about, we turn to people who (seem to) know more about it. One such example is going to a doctor when being ill. Not everybody is able to get a degree in medical science, so when we feel ill, we turn to those people who got such a degree. For the record, I will happily go to a doctor when I am ill, knowing that medical science, while not perfect, is rather reliable and if I listen to the advice of the doctor, chances are that I get well again.

My eyes started to roll when the author of the article states that:

The same is true of climate change: most people defer to the expert consensus of climate scientists.

It suggests that the authority of climate scientists on the climate system is on par with the authority of medical scientists on the human body. As it is worded here, I get the impression that the ball switched from one shell to another. Sure, I trust my doctor, but that is not necessary because I trust the expert consensus, but because I trust that his advice will work and/or is proven to work. The expert consensus has a different quality for the two. It all depends on what exactly those scientists agreed on. Expert consensus could even be quite meaningless when the definition of what they agreed on is not very clear.

Generally, I have no problem believing that there are similarities between the two sciences, but there are also some substantial differences. For example, there are huge differences when it comes to the quantity and quality of not only the experience with their subject, but also the evidence that have been found.

Medical science has a much longer history than climate science. For example, the first university in Belgium was founded in 1425. It then had only four departments and Department of Medicine was already one of them. Medical science was rather crude back then, it depended on things like herbs, potions, bloodletting and so on. Medical science came a long way since then. Many billions of patients were treated (some successful, others not so much), many experiments were performed, many questions answered, many secrets unraveled and many difficulties overcome. Adding to the accumulated knowledge over many centuries, probably even close to a millennium.

Compare this with climate science that is a relatively young science. It only got some traction in the second half of the 20th century and is studying the long-term effects of our climate system. To do that, they only have reliable data from the last decades. Before that, there were crude, spatially uneven and incomplete measurements of local temperatures, precipitation, sea level rise,… The longer we go back in history, the worse the reliability gets. Looking at for example the NASA dataset that changes so frequently, it seems that the assumed global temperature depends more on the assumptions made than the actual measured values.

Before direct measurements were taken, the scientists can only rely on proxy data, which are not direct measurements of some parameter, it are measurements of values that have some relationship with the measured parameter. For example, tree ring measurements are not direct temperature measurements, but measurements of the growth of that tree. Theoretically, the bigger the tree ring, the bigger the growth and this growth is somehow related to temperature. But there are also a number of other (unknown) parameters in play. Growth also depends on the availability of nutrients, competition with other plants/trees/animals, the availability of water, infections, the presence of toxic elements, infestations and many, many others. The actual signal is diluted due to the noise of the other parameters.

Medical science also has the same problem of studying a complex, coupled, chaotic system, but they have vastly more subjects that were treated. Many cures for many diseases were tried and tested. In climate science there is only one planet, so nothing can be tested. That is were modeling comes in. By varying several parameters in a mathematical model, scenarios could be tested, but the quality of that evidence is much less than medical science.

Another problem is fitting together the data with different resolution. Even if we assume that the crude, unevenly & spatially incomplete datasets and proxy datasets are all correctly measured and interpreted, then we still have several datasets with different resolutions that can’t be reliably fitted together.

By the way, who are the experts? In medical science, those are relatively simple to spot: your doctor will have a degree in medical science, no doubt about that. In climate science that is a lot less transparent. Do you need to be a physicist, a statistician, a mathematician, an ecologist, a geologist, an all-rounder,…? To make matters even more complex, there are even people from Greenpeace and other organizations who call themselves “climate experts”. Heck, here in Belgium, we have a pupil of Al Gore who is presented by the media as a “climate expert”.

So could you reliable compare such a young, multidisciplinary science, working with only one patient, with limited/only recent reliable data, with limited experience and with huge uncertainties, be reliably compared with a many centuries/one millennium old science that has a long track record with many patients, many experiments, many cures that work and others that are known not to work? Both deal with a intrinsic complex systems, but one has a huge amount of practical experience, while the other has to rely on Theoretical models of their subject.

Okay, you get the drift. The two sciences are rather different in quantity as well as quality of the experience and evidence, therefor is it rather misleading to state that a climate scientist has the same authority on how the climate system will evolve (in 100 years) as a medical doctor on his patients. To correctly compare the two sciences, we have bring medical science to the same level of climate science.

Suppose you feel ill and go to the doctor. Now the doctor says that, although you don’t feel that bad right now, you are suffering from a really serious disease.

Would you trust your doctor when you know that medical science only had one patient with this specific disease (you) and that it was not really clear whether you are actually sick or not. This because only few measurements were taken from you in the past (or were badly recorded) and the doctors don’t yet know what your healthy parameters are, since the recorded parameters were only measured AFTER the alleged start of the disease.

Would you be more relieved when you know that he consulted a bunch of his colleagues on different occasions and at every consultation between 90 to 100% agreed that his diagnosis of your illness is correct? What when you know that to come to that consensus, those consensus doctors lumped together this horrible disease with some other innocent diseases, therefor inflating the consensus, yet, for whatever reason, didn’t disclose this important information to you?

Would you uncritically willing to pony up an insane amount of money to get cured of this horrible disease when it is impossible to check whether that expensive cure actually works?

What if you know that the symptoms are not well defined: every symptom (or the lack thereof) can be used as an indication that you contracted this horrible disease?

Would you trust your doctor when you know that he is making one-sided claims about the illness and its cure. For example, he only mentions the horrible sides of the disease (ignoring important nuances) and only tell how good the cure is (ignoring the possible side-effects of the cure)?

Would you trust your doctor when you know that he gets more attention, funds and prestige when he diagnoses that disease more often and that the media loves the doom stories he is telling?

Would you trust your doctor when you know that he doesn’t not have a medical degree, but is the pupil of a famous politician who is earning big bucks by advocating on this disease? Hey, he adheres to the consensus, so he can’t be wrong…

And so on and so on.

I don’t know about you, but in such cases, I would have less trust than I would have when I go to a medical doctor.

Don’t get me wrong. I am not claiming that climate science has no abilities or is not making great strides. In the short timespan it surely collected huge amounts of data and adding a lot to its accumulated knowledge. But to suggest that it can speak with as much authority as medical science is downright ridiculous.


2 thoughts on “The doctor’s analogy: people defer to the expert consensus of climate scientists

  1. manicbeancounter

    I believe that climate science can be tested even when we have complex systems and very imprecise data. A way to discern if the “climate” is truly a science is to check the predictions made some time ago with the outcome. In 1988 Hansen et al made forecasts of global temperature rise based on 3 emissions scenarios.
    “Scenario A assumes continued growth rates of trace gas emissions typical of the past 20 years, i.e., about 1.5% yr-1 emission growth; scenario B has emission rates approximately fixed at current rates; scenario C drastically reduces traces gas emissions between 1990 and 2000.”
    Clearly emissions have increased from around 35 GtCO2e in the mid-1980s to 49 in 2010 and 51.9 in 2016 (UNIPCC/UNEP figures). It is much nearer to Scenario A than to B. Despite that cumulative emissions (which are relevant to warming) are quite close compared to C. But warming is most closely related to C. Reality has failed to conform to the predictions, so the hypothesis that human GHG emissions have a major impact on global average temperatures is contradicted by the evidence.
    On the other hand, much of the advances in medical science have been learnt more from looking at the data than having a testable hypothesis. An extreme example is Ignaz Semmelweis, who looking at the statistical found that handwashing massively reduced mortality rates in the maternity hospital he administered. It was a few years later that Louis Pasteur proposed germ theory. Semmelweis’s observations (well documented in published papers) conflicted with the established scientific and medical opinions (or consensus) of the time.
    From my history at school (40 years ago) other areas of medicine where development has come through observations are the use of small quantities of cowpox virus by Edward Jenner to innoculate against smallpox, after he observed that milk maids who had contracted cowpox failed to get smallpox. Another is the development of penicillin by Alexander Fleming.
    Antiseptics, vaccines and antibiotics have not developed by consensus, but by observations. So could our understanding of climate (or an understanding of the extent of our collective ignorance) if it were not for the purveyors of consensus blocking out observations of the natural world.


    1. trustyetverify Post author

      I saw many analyses of the Hansen model (by the way, I liked yours). It was really fun to watch how the two two sides could come to a massively different conclusion. One side confirmed that Hansen was right, while the other side found he was off the mark.

      Concerning this post, I too think that despite the complexity and the lack of reliable historical data, some tests could be performed. Climate science also has the advantage that it grew in an era of rapid scientific progress, while medical science had to evolve incredibly slow over many centuries.

      The point of the post is that there (still) is a huge difference in quality & quantity of evidence and also that there are some inherent limitations that have to be taken into account (yet aren’t). Therefor, the suggestion of the skepticalscience author(s) that climate science has the same authority on the climate system as medical science on human health, is not warranted.



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