Can you trust consensus in science

The illusion of scientific consensus


By Christian Lévêque

Photo: FDA via Flickr

The notion that one has to listen to “science” because it is rational and thus a guarantor of “truth” is widespread. But that's not how scientific research works.

The major environmental issues (climate, biodiversity, pesticides, GMOs, Covid-19, etc.) give rise to many controversies in which social groups with different objectives are involved. We are witnessing a flood of more or less certain assertions, speculative assumptions, even misconceptions and beliefs on subjects that undoubtedly deserve great attention. In this context, who will be able to play the role of arbiter between the parties involved in resolving the issues at stake?

The idea that one has to listen to “science” because it is rational and thus a guarantor of “truth” is fairly widespread. In debates we often see these key arguments used: "Science tells us ..." or "There is a consensus among scientists to say that ..." or "It is scientifically proven that ..." , etc., giving the impression that science has spoken and mass has been read. Does that mean that science, like the Pope, is infallible? And yet the same society that questions science when it suits it encounters the innovations resulting from science more and more critically, as we have seen on the subject of GMOs.

But the naive idea of ​​a science that stands above conflicts and is able to distinguish between true and false is far from reproducing reality. Rather, it is an expression of a deep misunderstanding of how the world of research works. On the one hand, science can make mistakes, as it has done many times before. On the other hand, the search for knowledge and the search for causality on issues that are still poorly understood is a difficult undertaking that involves observations, experiments, interpretations, etc., and often calls into question the original explanatory hypotheses. What appears to be true today will not necessarily be true tomorrow, so “certainties” among scientists are often “relative”.

Science can be wrong

By the 18th century there was a consensus that the world was created by God. Scientists did not question creationist dogma, and Linnaeus, the Swedish scientist who introduced the binary nomenclature of living things, stated that he was taking stock of God's work. The belief in an immutable and perfect nature is still alive despite all evidence to the contrary. For a long time, people also believed in spontaneous conception. After much debate, Pasteur finally put an end to this belief. Let us also remember that at the beginning of the 20th century there was a consensus that Wegener's continental drift theory had been refuted, but that a few decades later this would become the origin of the theory of plate tectonics.

"The idea of ​​a science that stands above conflict and is able to differentiate between true and false is an expression of a deep misunderstanding of how the world of research works."

Not so long ago we only talked about solar cycles and Milanković's theory when it came to climate. We have since discovered the anthropogenic impact. But can one speak of a consensus on climate? That is doubtful, and the fact that those who dare to challenge the prevailing view are marginalized certainly did much to stall the debate. But there are still a lot of ambiguities in this as in other areas, as some authors have noted. Are all opinions expressed by other scientists inadmissible?

Why is there uncertainty in science?

A big issue at the end of the twentieth century was the recognition of the extraordinary complexity of the world: the complexity of ecological systems and living organisms, the complexity of human societies, the complexity of the planetary system and so on. In common parlance we use the term “complex” to express that the object under consideration eludes a simple description. This acknowledges that it is "complicated" and that it is difficult to analyze. But in scientific parlance, complexity means that every system consists of elements that interact with each other in a variety of ways, and that the result is not easily accessible to simple understanding. While we have long assumed that a cause always corresponds to an effect, today we are confronted in many areas with the fact that the dynamics of systems depend on several parameters and with the difficulty of recognizing their respective roles. Not to mention the fundamental role random phenomena play in the dynamics of ecological systems, as Jacque Monod reminded us

This is how the physicist Werner Heisenberg formulated the principle of indeterminacy, the essence of which can be summarized as follows: In life, as in quantum mechanics, we are always confronted with uncertainty. As a consequence, much of the debates about conflicting hypotheses result from difficulties in interpreting observations made in contexts where the time and space scales are intertwined, the effects may be delayed, and the possible interactions between the parameters are unknown. This phenomenon is best known in the field of epidemiology: A symptom can be the result of several causes without it being possible to determine which of them play a decisive role. Such a system can be compared to a black box in that we have great difficulty understanding the internal mechanisms of how it works.

"A symptom can be the result of several causes, without it being possible to determine which of them play a decisive role."

In the discussion of pollination and bee deaths, there is no doubt that insecticides do play a role, but contrary to the claims of some activist groups, they are not the only factors. The focus, however, is on the harmful effects of the pesticides, ignoring the other factors involved. A biased approach, in contrast to scientific deontology, which looks for the causes without preconceived notions. We are faced with:

"[...] the inefficiency of our way of knowing and teaching, which teaches us to separate things from one another (objects from their environment, disciplines from one another) and not to connect them, which are nevertheless 'interwoven'. An intelligence that only knows how to separate divides the totality of the world into incoherent fragments, divides problems. As a result, the more complex the problems become, the greater the inability to think about them in complex ways; the more global problems arise, the more incredible they become. Unable to imagine the context and the planetary complex, intelligence becomes blind and irresponsible. " (Edgar Morin, “Relier les connaissances”, 1999) 2

It should also be noted that the search for causality in such contexts presupposes that there are qualitatively good observational data on the many parameters that can have an effect over long periods of time. The famous long-term series of observations that all naturalists dream of and that are so often missing. First, it seems that such research costs too much. Second, it takes time to gather actionable information, and it isn't worthwhile for publication either. While there are observatories and employees in climatology, astronomy or geophysics who deal with long-term measurements, there is nothing comparable in the life sciences.

"Nature doesn't work like a machine."

It should be added that many studies have clarified the role of random phenomena in system dynamics. Nature does not function like a machine, and the mechanistic and deterministic approach to the functioning of ecological systems that has long prevailed is obsolete. The implication is obvious: in this environment it is difficult to predict medium and long-term developments because we do not have the tools to do so. Yet some “scientists” cannot resist the temptation to play the oracle.

As observers, we therefore face great difficulties in analyzing and interpreting the often disparate and incomplete data available to us. Many meta-analyzes, on closer inspection, report the difficulty of accessing data on parameters considered important, often concluding that further or even more research is required. Nonetheless, the generally cautious conclusions of scientists are often translated into high-pitched and alarming accounts by the media.

Questioning is welcome

Challenging a majority theory at some point is not heresy, but part of the scientific debate. Finding the “truth” is not necessarily achieved through consensus, but through an interplay (one could say: trial and error) between an explanatory model and the observed facts. The scientific approach therefore feeds on questions, critical thinking and doubts. It is possible that different observations in a different context may lead to different results and thus different interpretations. And the truth generally does not lie on either side.

"Challenging a majority theory at a certain point in time is not heresy, but part of the scientific debate."

Refutability (or falsifiability) is a concept introduced by Karl Popper3 that is considered the basis of scientific epistemology. Every hypothesis, every assertion must be refutable, i.e. it must be possible to contest it in order to test its validity. If a competing hypothesis proves more appropriate to describe a phenomenon, it takes the place of the previous one. In other words, the scientific approach is to make sure that the facts match the theories that are trying to interpret them.

At a certain point in time, knowledge about a phenomenon can solidify, even if uncertainties persist and a credible alternative hypothesis is missing. But it can never be ruled out that technological advances will lead to the acquisition of new knowledge that will allow further knowledge to be gained.

The wrong consensus of the UN conferences and the role of environmental NGOs

From time to time the UN holds major conferences on important environmental issues such as climate and biodiversity. In accordance with the UN procedure, scientists from all countries are invited to discuss in working and editorial groups. In principle, they are responsible for the topic to be treated, but on different levels. In order for it to be politically correct, all countries in the world must be represented. But the big international NGOs also have their place, as do the “politicians”, and their influence is anything but negligible.

For example, there are official links between the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) and the International Union for Conservation of Nature (IUCN). Without wanting to lapse into sterile polemics, since the participation of NGOs in the public debate is perfectly legitimate, the fact remains that the IUCN, which represents nature conservation concerns, is not a research organization and cannot claim to have a neutral position in this area .

"The recommendations for the conservation of wetlands emerging from these working groups are skewed by 'strategic' considerations."

This is evidenced by the position of the IUCN and other major NGOs on wetlands, an issue with which I have some experience. During the international working groups under the auspices of the UN, in which I participated in both the Biodiversity Assessment (1995) and the Millennium Ecosystem Assessment (2001-2005), it became apparent that the facts that the Protection of wetlands appeared problematic, were dismissed. This is a deliberate hiding of a sad reality: wetlands in the tropics are a major source of parasitic diseases. We also avoid talking about methane emissions from wetlands, which are far from negligible. As a result, the recommendations for the conservation of wetlands that emerge from these working groups are skewed by "strategic" considerations as they deliberately ignore some of the issues at stake.

In this context I have spoken of “selective sorting”, in which only the knowledge available is taken into account, which corresponds to the ideology advocated by the NGOs. This corresponds to the “confirmation bias” described by G. Bronner: We visit the Internet less to obtain information than to find arguments that support our convictions.4 In any case, the UN conferences are dominated by large NGOs, and their conclusions are by no means objective. If there is a consensus, it is political, not scientific! I do not mean by any means that wetlands should not be protected, I am only saying that transparency is far from the rule and that the formation of opinion is therefore manipulated by omission. One answer might be to combine wetland protection with a public health program in tropical environments. But of course that would cost more, and we hardly talk about it.

A consensus brought about by exclusion

Throughout history, scientific debates have always been passionate. Think of those who revolved around Darwin's writings and his theory of evolution. We also see this in the areas of climate, biodiversity, and biotechnology - often accompanied by mutual denigration, if not more.

“The UN conferences are dominated by large NGOs and their conclusions are by no means objective. If there is a consensus, it is political, not scientific! "

So if you dare to ask questions about the real effectiveness of homeopathy, you have every chance of being accused of being in the pay of the pharma lobby. And if you claim that GMOs are a promising area of ​​research, you will be mistaken for a Monsanto agent. Likewise, anyone who is reminded of the academic consensus on the risks associated with synthetic pesticides under normal conditions of use is classified as an agrochemical lobbyist. Questioning renewables can give you the reputation of being an agent in the nuclear industry. If you criticize Mr Seralini's work, which has been refuted by recognized science, he will sue you! A good example of a scientific debate? And of course the slightest hint that we may not know all of the parameters to model climate change leads to the media branding you as a climate denier.

Scientists are increasingly being accused of maintaining contacts with industry, while at the same time being urged to do so by their supervisory authorities and in various national or European tenders. Research funded in this way is labeled as corrupted. The “conflict of interest” argument is used quite arbitrarily. For example, the ideological conflicts of interest that exist for scientists who are close to activist groups are never questioned. If, for example, one declares that ecology has to be a committed science, this clearly shows a bias that instrumentalizes science and places it at the service of ideologies. It is then difficult to believe that ecology can offer an unbiased view of environmental issues.

The combative attitude creates an environment of mistrust and ideologically motivated denunciation, which leads to a lack of transparency and the withholding of information. The result is a drying up of the debate and the establishment of a single doctrine. Here, too, we are far from a scientific approach, and yet this is the situation we see on most environmental issues. Even more frightening, some researchers who want to attract attention are engaging in these intimidation attempts.

"The ideological conflicts of interest that exist for scientists who are close to activist groups are never questioned."

A "political" role play

It is strange, to say the least, that the social groups that marginalize scientists who question the causes of climate change or the reality of the sixth mass extinction in terms of biodiversity are often the same groups that reject GMOs on the pretext of being them dangerous to health, although this technology is considered harmless by the majority of scientists. The reality is that they don't trust science if it doesn't conform to their ecological ideology. They only refer to science when it speaks in the sense of the views they defend (e.g. on climate change).

It is also curious that those who oppose glyphosate - the health effects of which are far from dramatic if the conditions of use are followed - do not appear to be as zealous about tobacco, alcohol and narcotics, which cause tens of thousands of deaths in France every year (The facts are beyond dispute, there is scientific consensus on this). But alcohol consumption is fun and good for the economy? Just as it has been proven that cars kill, injure, pollute. But we stand up against the price of gasoline, not the car.

In the search for alternative energies at any price, many approaches are pursued that are no less obvious than the use of nuclear power. Let us remember the enthusiasm for biofuels at the end of the 20th century, which subsided significantly when we calculated the areas that had to be cultivated to meet only a small part of our needs. And what about the huge masses of concrete that are needed to install wind turbines, but whose ecological or dismantling costs have not been calculated? The silence of the ecologists is telling.

"The combative attitude creates an environment of mistrust and ideologically motivated denunciation, which leads to a lack of transparency and the withholding of information."

Indeed, in all eras, social groups have tried with conviction to impose their ideology against all scientific evidence. I do not want to deal in detail here with the religious wars that continue to this day. But what to make of the fact that nearly 40 percent of Americans and 75 percent of Saudi Arabians cling to creationist theories? What should we think of the information that 16 percent of Americans today think planet Earth is flat, as do 9 percent of French? These people even hold conferences. Should we really assume that we can convince these “believers” that science does not validate the fables of the Bible? Of course not, and we face a real dilemma that turns the search for consensus into a remote utopia. But this is exactly what is suggested to us again and again. No compromise is possible because we do not speak the same “language” at all.


The science that has replaced magical thinking in trying to explain how the world works is a constant search for the causes and consequences of the natural or social processes we observe. It progresses in stages according to the accumulation of knowledge and technical progress, but also through the increasingly necessary integration of many parameters that work together synergistically. The romantic image of the lonely and ingenious researcher is largely out of date due to the need for collaboration between many disciplines. In this iterative process, it is not surprising that yesterday's truths also evolve. That is why science can only say: "With the current state of knowledge we can claim that ..." That is why it is also normal and salutary when dissenting opinions can be expressed.

The necessary prudence often seems not to be observed because the media, public opinion and managers demand “certainties” and there is much talk of intermediate goals, which are then overemphasized and instrumentalized in order to meet these expectations. Many studies on the reasons for the decline in biological diversity point to the interaction of several factors, including habitat and landscape changes, climate, urbanization, pollution of all kinds, parasites, etc., whose respective roles are difficult (and unreliable) to assign globally is to determine. Still, some stakeholders reduce this variety of causes to the effect of pesticides alone, which have become their obsession. Without evaluating the economic and social consequences.

"The model has taken the place of the astrologers."

Another consequence of the uncertainties inherent in the scientific process is that forecasting becomes a difficult endeavor. In the case of GMOs, for example, it is just as difficult to prove that they pose a risk as it is to prove that they are harmless. In the debates, opponents take advantage of this uncertainty to turn the argument around: "If you cannot prove to me that it is not dangerous, then there are concerns ... THIS is how you are putting us at risk." A circular argument that the debate does not advances. But we can see that GMOs have been consumed by humans and animals for two decades with no evidence of any health consequences. On the other hand, the fact that organic farming is responsible for the deaths of more than fifty people in Germany and that hundreds of them have been admitted to hospitals has not been made public. This is the other side of manipulation, the targeted selection of information by interest groups who primarily aim to enforce their ideology.

In other areas such as climate and biodiversity, medium and long-term forecasting is anything but an easy undertaking. The model has taken the place of the astrologers.5 While the model is undoubtedly a useful tool for formalizing knowledge and contributing to reflection, its establishment as a prospective tool is a mistake because the future is constrained by random events that the Model cannot integrate. At least one should be very careful when using models (based on the current state of knowledge), which is unfortunately often ignored. Nonetheless, it is to be welcomed if the IPCC uses a probabilistic approach to deal with these uncertainty issues by making recommendations based on the concepts of evidence and consensus to qualify the uncertainty levels of the announced trends. The level of evidence is classified as limited, moderate, or robust according to the level of evidence provided by the particular theory, observation, or model. The level of agreement is rated as low, medium, or high depending on how much the experts agree given the material available to them.

In conclusion, we need to get out of the ghetto of preconceived notions that every social group has a single "truth" that it tries to enforce. "Science Said" is a political statement meant to hide the bias. Ultimately, the point is to return to the idea of ​​decision-making in an uncertain universe that contributed to the development of the precautionary principle. And not the one that is used today to prevent innovation. But one that says that when we have questions about the consequences of an innovation, we take the necessary precautions to monitor its implementation to ensure that there are no adverse consequences.6 This is a matter of common sense, actually Consensus should be. Instead, we have to deal with GMO "field liberators" who want to use brute force to destroy any findings that could be obtained through field tests.