Claims that ‘the science has spoken’ and ‘the science is settled’ are based on the false idea that climate scientists follow the same scientific standards as traditional scientists. They don’t

By Paul MacRae, January 22, 2024

Those who dare to question or criticize the apocalyptic claims of the Intergovernmental Panel on Climate Change (IPCC) (“if we keep adding carbon to the atmosphere we’re all gonna fry,” basically) are told “the science is settled” or “the science has spoken.”

We’re told “the science” is the product of a “consensus” of more than 2,000 climate scientists who contribute to the IPCC’s reports; and we’re told this “consensus” is not to be questioned by non-scientists or even scientists from other disciplines because, again, the science is “settled.” Anyone who says otherwise is a “climate denier.” End of story.

And, indeed, that would be end of story—if the “science” of climate change was as strong as its followers claim.

Unfortunately for its disciples, orthodox climate science is not— as we (the public, politicians and media) are strongly led to believe—traditional science, the kind of science that has been incredibly successful at determining what is real and what is not, in the process improving our lives in countless ways.

Instead, orthodox climate science follows a brand of science known as “post-normal” science, and “post-normal” science follows standards that are quite different from the standards of traditional, “normal” science.

‘Post-normal’ science

What is ‘post-normal’ science? Wikipedia describes it as follows:

Post-normal science (PNS) … is a problem-solving strategy appropriate when “facts [are] uncertain, values in dispute, stakes high and decisions urgent,” conditions often present in policy-relevant research. In those situations, PNS recommends suspending temporarily the traditional scientific ideal of truth, concentrating on quality as assessed by internal and extended peer communities. [emphasis added]

The conclusions of post-normal science aren’t ultimately based, then, on empirical data, with theories that can be rigorously tested and falsified, but on “quality as assessed by internal and extended peer communities,” i.e., “consensus,” i.e., informed guesses.

While traditional science aims to separate what scientists believe is true from what is actually true, “post-normal” science takes us back to a less reliable stage of science in what scientists believe to be true is the Truth.

The IPCC is quite explicit about its reliance on the post-normal approach, without using the term, in its 2001 report:

We fully recognize that many of the evaluation statements we make contain a degree of subjective scientific perception and may contain much “community” or “personal” knowledge. For example, the very choice of model variables and model processes that are investigated are often based upon the subjective judgment and experience of the modeling community.1 [emphasis added]

IPCC contributor Mike Hulme describes the IPCC’s “subjective” approach to science this way:

Climate scientists frequently have to reach their conclusions on the basis of the partial, and sometimes poorly tested, evidence and models available to them. And when their paymasters—elected (or non-elected) politicians—ask them for advice, as in the case of the IPCC, opinion and belief become essential for interpreting facts and evidence. Or rather, incomplete evidence and models have to be worked on using opinions and beliefs to reach considered judgments about what may be true.2 [emphasis added]

In short, “opinions and beliefs” about the “partial and sometimes poorly tested” empirical evidence available, not empirical evidence itself, are the hallmark of “post-normal” science, including climate science. For climate scientists, what they (or some of them) believe to be true is the Truth.

Yet, if this is the case, if orthodox climate science is based on belief rather than empirical evidence, how can “the science” possibly be “settled,” “certain,” and not to be challenged, as orthodox climate science likes to claim?

‘Normal’ science: testing and falsification

In what other ways is this “post-normal” approach different from traditional, “normal” science?

For a start, traditional science is not “certain” about its conclusions—as Nobel-Prize winning physicist Richard P. Feynman put it, “A scientist in never certain.”3 Science is a rolling wheel of discovery that never stops because it is constantly self-critical,and therefore self-correcting.

Also, “normal” science relies on rigorous empirical testing, not with the aim of proving a theory but disproving it (also known as falsification), just as car companies put their vehicles through torture tests on the track to expose mechanical flaws. Only if a theory passes these “falsification” tests is it accepted within the discipline—but only until a better theory comes along. The science is never “settled”, as orthodox climate science likes to claim.

The importance of testing and falsification as part of “normal” science can’t be emphasized enough. For example, a first-year, university-level textbook on science notes: “The requirement that we be willing to subject our explanations to experimental tests is the distinguishing feature of science.”4 [emphasis added]

Similarly, a book of readings in the philosophy of science states that the key benchmark of “science” is testability: “If the propositions which express [scientific] claims are not capable of tests, we cannot call these propositions true or false or even how to go about establishing their truth or falsity.”5 [emphasis added]

The conclusions of orthodox climate scientists are not, by their own admission (see Hulme, above), “capable of tests.” This means, to put it simply, that orthodox climate science is not “science.”

‘Post-normal’ science relies on computer models, not tests

Under the IPCC’s “post-normal” theory, when CO2 goes up, so does the temperature; when CO2 goes down, the temperature goes down—the “control knob” theory.6

For orthodox climate science the correlation between temperature and CO2 is very strong, which means temperature is very “sensitive” to CO2 fluctuations.

Based on this “control-knob” theory, “post-normal” climate scientists make alarming predictions about our bleak future if we continue to use fossil fuels. However, their predictions of doom aren’t based on actual empirical data for a very simple reason: we can’t have facts from the future.

This means that climate-science predictions are based not on empirical facts that have been rigorously tested but on computer models that aim to predict what will happen if we keep putting carbon dioxide into the atmosphere (if X, then Y), based, again, on the theory that carbon dioxide is the “control knob” of temperature.

Hulme describes the resort to computer models this way:

The problem is that in areas of science which are seeking to understand the behavior of large complex systems which can’t be replicated in the lab, it is very hard if not impossible to apply the scientific litmus test of falsification through experimentation. And climate change is one such area of science. We have scientific theory, we have empirical observations. What we haven’t got are lots of different Earths that can be experimented on in controlled conditions. Virtual climates created inside computer models are the best we’ve got.7 [emphasis added]

Based on these computer-aided guesses, politicians are expected to radically retool Western society (in effect dismantle it) by eliminating fossil fuels ASAP.

Testing the computer models

Since we don’t have facts from the future, the only way of testing the IPCC’s models is to “hindcast” them, which means seeing how well the models worked in predicting climate over earlier decades. Did a climate model devised in, say, 1990, accurately predict the temperature variations (a.k.a., “climate”) between 1990 and, say, 2020? If so, you could conclude the model is accurate; otherwise, not.

So, in hindcast, how successful are IPCC’s computer models at predicting the climate? Have they passed the “tests”? The simple answer is no. Almost all the computer models used by the IPCC show much more warming than has actually occurred (see Figure 1).8 As you can see, from 1975 to 2020, the IPCC model predictions (spaghetti lines and the red trend line) are way higher than the actual measured temperatures (green lines).

Figure 1: Model predictions since 1975 (spaghetti lines and red average line) compared to actual measured temperatures (green lines plus average line). Source: John Christy.

In traditional science, with test results this far from reality, the “control-knob” hypothesis that carbon dioxide is causing increased (indeed, potentially catastrophic) warming would be decisively falsified. However, that’s not the way post-normal science works.

In post-normal climate science, these failed model test results are shrugged off; “we just need to design better models,” the scientists say, and carry on as before. There is no way to actually falsify the theory, as in traditional science. Climate scientists just keep bashing away until (they hope) the theory is finally “proved.” This blasé attitude is perhaps best summed up by climatologist Chris Folland, who said: “The data don’t matter.… We’re not basing our recommendations on the data. We’re basing them on the climate models.”9 [emphasis added]

Compare Folland’s approach with that of Richard Feynman, a physicist following traditional scientific standards: “If it [the theory] disagrees with experiment it is wrong. In that simple statement is the key to science.”10

In IPCC climate science, by contrast, the theory (temperature is highly correlated to changes in carbon dioxide) disagrees rather fundamentally with the experiment (the models don’t match the actual temperature reality), but IPCC scientists refuse to abandon the theory. Instead, they double down and, to cover up the model shortcomings, vilify as “climate deniers” those who dare to point out the theory’s failures. The “science” is “settled” and “certain,” and therefore not open to criticism, and certainly not from lay people. For example, Richard Somerville of the Scripps Institute of Oceanography has written:

People who are not experts, who are not trained and experienced in this field [climatology], who do not do research and publish it following standard scientific practice, are not doing science.11

Of course, Somerville ignores the fact that official climate science doesn’t follow “standard scientific practice,” as we’ve seen.

Another key standard scientific practice that the “post-normal” climate science disregards is rigorous criticism of hypotheses over time before they are accepted as valid theories.

IPCC climate science immediately accepts ‘control knob’ theory

When the IPCC published its first report in 1991, it found no evidence of human-caused global warming.12

And the same was true of its second report. The original version of the second IPCC report, released in 1995, also stated that “no study to date has positively attributed all or part [of the climate change observed to date] to anthropogenic causes.” So far, at least some scientific standards preserved.

However, this and other sentences containing the same idea (no human influence detected) were taken out of the report and the following was inserted: “The balance of the evidence suggests a discernible human influence on global climate.” Which is, of course, the conclusion the IPCC wanted from the start.

This change was made, IPCC officials explained, “to ensure that it [the body of the report] conformed to a ‘policymakers summary’ of the full report.”13 Then-IPCC president Rajendra Pachauri defended this cart-before-horse process as follows: “We necessarily have to ensure that the underlying report conforms to the refinements [i.e., “review” by experts and government as part of the Summary for Policymakers].”14

In most scientific and business reports, the summary reflects what’s actually in the original document; the report isn’t changed to conform to the summary, as the IPCC did. But then, as we noted, the IPCC’s “post-normal” science doesn’t operate by the usual standards, scientific or otherwise.

The point here is that, a mere five years after the IPCC began its investigations, and had even initially acknowledged it could find no link between human-caused CO2 and warming, the IPCC fully accepted the theory that CO2 was the ultimate “control knob” of temperature (and therefore climate), and shrugged off any theories to the contrary as not only wrong, but sometimes “immoral”.15 As MIT astrophysicist Richard Lindzen  put it, global warming “is the only subject in atmospheric science where a consensus view has been declared before the research has hardly begun.”16

We don’t put new medicinal drugs on the market without years, sometimes decades, of testing to ensure they aren’t harmful. The IPCC did not feel a similar extensive round of testing was necessary before accepting “Net Zero by 2050” climate policies that could be, and already have been, extremely harmful to Western industrial society and its people. Meanwhile, those who point out these harms, and the weakness of the theory, are dismissed as sinful heretics.

‘Post-normal’ climate science seeks to avoid criticism

Logic suggests that if I, as a scientist in any discipline, was forced to use non-falsifiable, “post-normal” science based on a subjective “consensus” of experts, rather than direct empirical and rigorously tested evidence, I’d be especially willing to hear and debate alternative theories; I’d be especially aware of the need to avoid claiming “certainty”; and I’d be especially eager to have my results confirmed or refuted by other scientists, even if those scientists were skeptical.

More: I’d aim to create a Red Team/Blue Team approach to my research and results: a group of fellow climate scientists, but a Loyal Opposition if you will, that deliberately seeks holes in my “consensus” argument. This is how traditional science works (at least, ideally).

If nothing else, I’d demand that the IPCC reports include minority opinions, perhaps as appendices; it is quite simply beyond belief that the “2,000-plus scientists” who contribute to IPCC reports could have full unanimity on an issue as complicated as climate. So, what do the scientists who contribute to IPCC reports disagree on? Doesn’t the public have a right to know this rather important information? You won’t hear it from the IPCC or its supporters.

But then, I’d be assuming that alarmist climate scientists accept the traditional, skepticism-based approach to science; happily, the “post-normal” approach relieves climate scientists—at least in their own minds—of many of the burdensome professional and moral responsibilities of traditional scientists.

Traditional science vs. ‘post-normal’ science: A checklist

So, just to sum up, what do we know about the differences between traditional and “post-normal” science? They are summarized in the table below.

Seeing these differences, is it reasonable to accept “post-normal” climate science as so “settled” and “certain” that it is completely accurate about its conclusions and therefore beyond criticism or question, including from non-scientists? And shouldn’t we be especially wary when this science, with its attack on fossil fuels, threatens the very foundations of Western-style civilization?

Western-style civilization is based on traditional science and its ability to separate belief from fact—not always correctly, of course, but most of the time. In the same vein, traditional science attempts to create a separation between empirical, scientific facts and religious beliefs.

“Post-normal” science, by contrast, reverts to belief as the source of its Truth since it cannot definitively separate fact from belief (“subjective judgment”) and, much like religion, ultimately relies on faith.

That doesn’t mean the climate doomsayers are wrong; they may be quite right; perhaps we do face a climate apocalypse if we don’t mend our fossil-fuel-spewing ways. But if the “control-knob” theory is correct, it’s because the scientists made the right guess about the strong correlation between carbon dioxide and temperature, not because there is ample factual evidence to support their apocalyptic predictions (indeed, what factual evidence we do have points the other way: as we saw in Figure 1, temperature and CO2 levels are very poorly correlated).

If we don’t want Western-style civilization to collapse—and, by the way, many IPCC supporters, including the United Nations, do seek this outcome!—then we have a duty to be critical of “post-normal” climate science and its conclusions; we have a duty to demand evidence of a “climate crisis”, evidence that is based on traditional scientific standards. If we did so, one result is highly likely: if climate was examined using traditional scientific methods, the so-called “crisis” would disappear.

My advice when confronted with climate scientists’ claims that “the science has spoken”? Listen respectfully, and then demand concrete, empirical evidence. None will be forthcoming. Without such evidence, “the science” is, quite simply, not science.

This is a summary of Chapter 9, Real Science Vs. ‘Post-Normal’ Science, from Paul MacRae’s book Through the Looking Glass: A Citizen’s Do-It-Yourself Guide to Climate Science, available at Amazon in Kindle print and e-editions, and at other outlets such as Apple Books in e-edition format.


  1. IPCC, Climate Change 2001: Model Evaluation, “What is Meant by Evaluation?”, Section 8.2.2.
  2. Mike Hulme, “The IPCC, consensus and science.” Feb. 19, 2010. Mike Hulme website,
  3. Richard P. Feynman, The Pleasure of Finding Things Out: The Best Short Works of Richard P. Feynman. Cambridge, MA: Persius Books, 1999, p. 111.
  4. Martin Goldstein & Inge Goldstein, The Experience of Science: An Interdisciplinary Approach. New York: Plenum Press, 1984, p. 4.
  5. E.D. Klemke, et al., Introductory Readings in the Philosophy of Science. Amherst, NY: Prometheus Books, 1998, p. 32.
  6. Andrew A. Lacis et al., “Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature.” Science, Oct. 15, 2010, pp. 356-359. Available online but often behind a pay wall, although there are repostings on some public websites. For a summary of Lacis’s paper see
  7. Mike Hulme, “The IPCC, consensus and science.” Feb. 19, 2010.
  8. Clintel.
  9. Quoted in Patrick J. Michaels, Sound and Fury: The Science and Politics of Global Warming. Washington: Cato Institute, 1992, p. 83.
  10. Richard Feynman, The Character of Natural Law. Cambridge, MA: MIT Press, 1965, p. 156.
  11. Richard Somerville. “A response to climate change denialism.” Scripps Institute of Oceanography, Jan. 14, 2010.
  12. IPCC, 1991, “Policymaker Summary of Working Group I (Scientific Assessment of Climate Change), p. 64. Available online. The report said: “The size of this warming (over the previous 100 years) is broadly consistent with predictions of climate models, but it is also of the same magnitude as natural climate variability.”
  13. The trickery is revealed in a letter by Frederick Seitz, “A major deception on global warming.” Wall Street Journal, June 12, 1996. Available if you have a subscription to the WSJ.
  14. Donna Laframboise, Chapter 22: “Science has (not) spoken,” The Delinquent Teenager Who Was Mistaken for the World’s Top Climate Expert. Ivy Avenue Press, 2011, Kindle edition. Note that the IPCC’s science is “reviewed by governments” at the stage of creating the Summary for Policymakers.
  15. Lawrence Solomon, “The ice-core man.” National Post, May 4, 2007. Available on the National Post website as part of the “Deniers” series. In this case, Polish climate scientist Zbigniew Jaworowski had dared to suggest that CO2 readings from ice cores were lower than the actual levels, casting doubt on the “control knob” theory. His funders declared his position “immoral” and fired him.
  16. Quoted in Robert C. Balling, Jr., The Heated Debate: Greenhouse Predictions Versus Climate Reality, San Francisco: Pacific Research Institute for Public Policy, 1992, p. xxvii.