Here’s a question to ask yourself and your students: what percentage of trained scientists have to accept that a knowledge claim has been proven before you yourself will consider it reasonable to accept it?  How many scientists have to be “certain” (that is, convinced)?  And the next, closely related, knowledge question is not about the scientists (and their degree of psychological conviction) but the knowledge claims themselves: how much certainty is necessary for scientific knowledge?


Certainty of shared knowledge in the scientific community

Recent news media summaries of the draft of a major international report on climate change provide a good example of the ways in which “certainty” functions in scientific investigation.  The Fifth Assessment Report, from the Intergovernmental Panel on Climate Change (IPCC), a United Nations body of prominent climate scientists, will be available on September 30, but already a draft has provided a beautifully clear illustration of increasing certainty within a community of shared knowledge.

Scientists have become increasingly convinced of the central claim of climate science, namely that the recorded rise in global temperatures is “anthropogenic”– that is, caused by human activity.  In 1995, just over 50% of experts believed that that was the case.  By 2001, that percentage was 66% and by 2007, 90%.  Now?  95%– though not, it is to be noted, 100%. We can equally find historical examples where that crucial percentage has increased only very slowly, or fluctuated, or increased only to decrease later. Rarely, though, has the actual rate at which a group of experts has accepted knowledge claims been as clearly documented.

The numbers are also useful to point out to those students who have been told, as so many are, that the “the scientific establishment”, far from being a diverse body of independent minds, is unshakeably monolithic in its clinging to unchallenged certainty.

Certainty within the statements of the scientific community

The 95% figure is useful in other ways as a discussion point with students. Most probably know that few scientific claims (including the assertion that the earth is not flat) have 100% endorsement. On the flip side, they may not quite realize that scientists themselves characteristically express lack of complete certainty even when it is almost complete.  As Reno Knutti, a professor at the Swiss Federal Institute of Technology in Zurich, says, “We have got quite a bit more certain that climate change …is largely manmade.”  “Quite a bit more certain?” 95% consensus — and he’s still saying “quite a bit”?  This is the cautious language of scientists—and, it seems, it is often misunderstood by the media to mean a much greater level of uncertainty than is intended.

What do you say to the student who insists (sometimes because of misunderstanding Messrs. Heisenberg and Einstein, sometimes because of misinterpreting the characteristic language of science) that science is cripplyingly uncertain?  For one thing, of course, we can point out that even these students would bet their lives (quite literally) on the near certainty of some science. Even the deepest science skeptics will drive over a bridge reasonably certain of such scientific principles as gravitational pull, the tensile strength of steel, and the stability of the triangle!

Still, they are right in a way:  as we know, scientists themselves rarely claim 100% certainty. (Pseudo scientists, in contrast, rarely do anything else.)

Certainty within complex systems like climate science

The case of uncertainty in climate science, however, is especially problematic, for several reasons:

1. Climate science is complex and interdisciplinary. As Reto Knutti, a professor at the Swiss Federal Institute of Technology in Zurich says, climate science is a lot more than physics: “You can’t write an equation for a tree.”

2. Ideological and economic interests are intense.

3. Many claiming to be experts or claimed by others to be experts have no credentials in climate science.

Uncertainty engendered by news media

planet130922And, to complicate matters, the voice that speaks to the “general public” is rarely scientists themselves but, most often, journalists. In fact, some summaries of the IPPC, unlike the one from Reuters referred to above, largely (or completely) ignore the increasing certainty amongst scientists and, instead, emphasize another major finding of the report—namely, that just as the causes of climate change become more certain, so does the ability to predict regional changes become more difficult than had been understood.  In the words of professor Knutti, “We’re less certain than many would hope about the local impacts.”

Consider, for example, how a summary of the IPPC report is presented in the media, placing emphasis not on the increased certainty of the major knowledge claim but on the increased uncertainty of the secondary one:  “Top global scientists admit global forecasts were wrong.” The Telegraph article is correct of course:  top global scientist are, indeed, clearly and forcefully correcting earlier regional forecasts (though it’s interesting how the Telegraph’s evident bias would be different if instead of using the word “admitting” they had used the words “pointing out” or even “claiming”).  Even ignoring the slanted language and the selective “cherry picking” that underlies this newspaper’s version, the fact is that this increase in scientists’ uncertainty about this side of the climate change science, makes a further contemporary example of the fact that, far from there being an unchanging “scientific establishment”, science is constantly on the prowl for evidence and, for the most part, willing to follow where it leads—even if it means being more certain about less certainty!

Here the key TOK term “shared knowledge” takes on an interesting crinkle.  In this example, we find scientists trying to increase the pool of “shared knowledge”, but many of the public not quick to dip their toes into that pool.  Partly, of course, the spread of scientific knowledge is complicated in the case of climate science (as it is with some other scientific issues, like vaccination) by disinformation.

In the case of climate science the public has to deal with the contrary claims of such privately–funded organizations as the NIPCC, whose acronym for the Nongovernmental Panel on Climate Change can be easily confused with IPCC (Intergovernmental Panel on Climate Change).  NIPCC findings have been published by the Heartland Institute and broadcast on Fox news.  (See Fox Equates Faux UN Climate Report With The Real Thing.)

And to be fair, the public seems to be ready to accept new shared scientific knowledge claims when they are not confronted with contrary claims or when those knowledge claims are about, for example, something as remote from their lives (and jobs) as a newly discovered exoplanet or extremophile bacterium. Still, if the public had taken a good TOK course they would be quicker to accept new shared  knowledge  by applying such basic principles as:

• considering the source of the knowledge claims

• considering the coherence principle (in this case consistency with the experimental evidence that physics has mustered, for example, about the effects of methane and carbon dioxide on solar rays passing through a closed system.)

However, problems with the gap between public certainty and scientists’ certainty do not stop there.

Uncertainty arising from cognitive biases

Here is where another recently published paper comes into play.  Essentially a study in cognition, this, according to the published abstract, is the conclusion:

Why does public conflict over societal risks persist in the face of compelling and widely accessible scientific evidence? …In our experiment, we presented subjects with a difficult problem that turned on their ability to draw valid causal inferences from empirical data. As expected, subjects highest in Numeracy — a measure of the ability and disposition to make use of quantitative information — did substantially better than less numerate ones when the data were presented as results from a study of a new skin-rash treatment [i.e. one with no political baggage.]….The second  experiment, involving a politicized issue, however, showed that even highly “Numerate” subjects were suddenly incapable of applying their skills. Thus the scientists concluded, these Numerate subjects used “their quantitative-reasoning capacity selectively to conform their interpretation of the data to the result most consistent with their political outlooks.”

Even in the face of convincing evidence, therefore, it seems, most of us are determined to rationalize our way to where we really want to go—and, in the case of climate science, to a position that meshes less with evidence than with our own ideology.

The way forward with uncertainty

How, then, can we deal best with all of these factors affecting our understanding of certainty over scientific knowledge claims: the degree of consensus of scientists, the presentation of uncertainty in the media, the degree of acceptance in the general public, and our own cognitive biases that incline us to reinforce the beliefs we already have?

We have to recognize that there is a difference between the certainty of the truth of knowledge claims and the psychological certainty of believing them.  All knowledge claims in science have the possibility of being overturned with further evidence; it is part of the very nature of science that it is open to challenge and revision, and that knowledge claims based on evidence shift with changing evidence.  As Sophie Lewis and Ailie Gallant write:

Ultimately, the only scientific certainty is uncertainty. At times, these inevitable scientific uncertainties have been framed as synonymous with doubt and used to try to discredit findings.

But uncertainty is not a weakness of science. Rather than eroding our scientific confidence in human-caused climate change, using probabilities to talk about scientific uncertainties allows scientists to communicate findings more precisely and transparently.

The knowledge claims of science do change.  But when is it reasonable to accept them?  When is it reasonable to be psychologically certain – that is, believe them, or be convinced?

In the ideal, scientists aspire to the condition of mind of one of the science greats, Johannes Kepler. When evidence accumulated against a conclusion he had reached, he changed his mind: “When Kepler found his long-cherished belief did not agree with the most precise observation, he accepted the uncomfortable fact.  He preferred the hard truth to his dearest illusions; that is the heart of science.” Carl Sagan in Cosmos (PBS television series)  What compels scientists to reject knowledge claims in science, or accept them, must always be the extent of the evidence.

Clearly, the current UN report in climate science (the official version to be released at the end of this month) offers a splendid example in discussing “certainty” that follows the evidence (even if never reaching 100%) and “scientific consensus” that increases as the evidence increases.  Students might enter through questions of increasing breadth such as those below, moving from the specific example of climate change toward what we aim for in TOK class — a greater understanding of scientific knowledge.

When 95% of climate scientists expert on matters of climate change accept – on the basis of their evaluation of evidence — that climate change is happening and that human beings are causing it, is it reasonable to accept this knowledge claim yourself?

How does the shared knowledge of the scientific community, in this case and others, mesh with your own personal knowledge?

What is the meaning of “scientific uncertainty”?  How does it apply to scientific knowledge claims, and their very nature?  How does it apply to scientists themselves, as they weigh the evidence?

And how does climate science, in this regard, provide simply one example of the general methodology of the natural sciences — and the way it is understood, or sometimes misunderstood, by the general public?


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Recommended articles on climate science and uncertainty

in The Conversation:

“Penguins can’t fly and humans are causing climate change: how scientists build theories”, 20 August 2013

150 years and counting: confidence in climate science, 21 August 2013