Scientific consensus – collective opinion of scientists

In the hierarchy of scientific principles, the scientific consensus – that is, the collective opinion and judgement of scientific experts in a particular field – is an important method to separate real scientific thought from junk science, pseudoscience, cargo cult science, and other fake beliefs.

I often discuss scientific theories which “are large bodies of work that are a culmination or a composite of the products of many contributors over time and are substantiated by vast bodies of converging evidence. They unify and synchronize the scientific community’s view and approach to a particular scientific field.”

A scientific theory is not a wild and arbitrary guess, but it is built upon a foundation of scientific knowledge that itself is based on evidence accumulated from data that resulted from scientific experimentation. Generally, a scientific consensus eventually leads to a scientific theory.

I have written frequently about the scientific consensus, because it is one of the most powerful pieces of evidence in a discussion about critical issues of our day – evolution, climate change, vaccines, GMOs, and many other scientific fields. 

Scientific consensus – all about the evidence

Let me repeat myself. The scientific consensus is based on the consensus of experts in the field based on the evidence, almost exclusively from peer-reviewed and published data. Since science is not a democracy, there is no formal vote, although respected scientific societies will often publish a public statement on the scientific consensus for a particular issue.

Now if you’re thinking that a bunch of cranky scientists get together in a room somewhere and hash out the particulars of the consensus, that’s not how it works. In reality, a scientific consensus constitutes a huge body of scientific studies that all agree with and support one another. Scientists come to this agreement as a result of the consistent evidence, not because of their personal opinions or a priori conclusions.

And, there isn’t a debate that forms the foundation of the scientific consensus. The only thing that matters to forming a consensus, or alternatively, demolishing said consensus, is evidence. And as I like to say, it’s the quantity and quality of evidence that matters. If a minority of scientists in the field make it seem like there is a debate, their opinion matters only if they provide the breadth and depth of evidence that could reverse the consensus.

Moreover, it’s important to note that a consensus, or its more formal cousin, a theory, are not dogma. They aren’t incontrovertible. They aren’t irrefutable.

When Charles Darwin described the basics of evolution 150 years ago, he didn’t know about DNA and genes. Our current description of evolution is more detailed and includes DNA. Evolution is a fact. And the level of evidence supporting the mechanisms of evolution are so, I cannot comprehend what it would take to challenge it.

The same with most other consensuses in science. Because I am openminded to information that might change the consensus, I can imagine a theory or consensus being overturned eventually. It’s just that the possibility is vanishingly small, because the evidence level that needs to be exceeded is so high, that it will require hundreds of published articles to begin the discussion.


How that collective opinion is formed

There are three criteria for an evidence based consensus, as distinguished from a typical political or group consensus (see Note 1):

  • Consilience of Evidence – Many different fields of science all contribute to the understanding of major scientific principles, such as anthropogenic climate change–ranging across biology, geology, chemistry, and other natural sciences. Our acceptance of the safety and effectiveness of vaccines is supported by research in diverse fields like epidemiology, public health, microbiology, immunology, virology and many others. It’s not one subspecialty of science that builds the consensus, it’s several.By contrast, the support for homeopathy, as an example, is restricted to just advocates of that pseudoscience. They don’t published their findings in any outside journals because they’re lacking a plausible mechanism to explain inverse dose-response, and they are incapable of providing favorable results in double-blind randomized control trials. They can establish nothing more than a placebo effect.In fact, since homeopathy would require a wholesale restructuring of our knowledge of quantum mechanics, chemistry, physics and other non-biological fields, the only way we would ever see consensus that homeopathy works would require broad support in numerous fields of science. And frankly, no one is on board, except the pseudoscience pushing crowd.
  • Social calibration – The experts involved in the consensus agree on standards for evidence–and this standard is ridiculously high, which is why it is so powerful. Those in the pseudoscience world reject certain gold standards of clinical research, like double-blinded, randomized clinical trials, which places a large barrier to having their “alternative medicine” ever reaching a scientific consensus.Moreover, there is broad and powerful evidence that creates a scientific consensus, something that is lacking in pseudoscience. We have consensus that homeopathic remedies lack any active ingredients and have no plausible biological mechanism. So the consensus does work both ways, to support scientific knowledge that is evidence based, and reject beliefs that lack similarly powerful evidence.
  • Social Diversity – Having researchers from many cultural and economic backgrounds provides diversity that helps eliminate social biases as a cause of error. For example, the published literature on the safety of GMOs has provided agreement from researchers in countries around the world from various cultural  backgrounds.If the evidence of safety only came from middle-class white scientists, whose parents are farmers, and who live in St. Louis, Missouri only 5 blocks from Monsanto headquarters, we might rightfully suspect the consensus. But in general consensus is formed by the weight of evidence, and to get that weight requires research from nearly everywhere on the planet.


Evidence, all about the evidence

Let’s be clear, gathering evidence that supports any scientific idea isn’t easy. And this evidence isn’t derived from a Google search, with no critical analysis of the quality. A scientific consensus is formed by experts, who are substantially more knowledgeable than most of us in the field being discussed.

As Steven Novella, MD, writes in his NeuroLogica blog:

For anyone trying to take a scientific approach to knowledge about the world, we must rely heavily upon experts, or those who are more knowledgable than we are. There is no choice – there is simply too much specialized scientific knowledge for anyone to be an expert in everything, or even a significant portion of scientific disciplines.

Further, being an educated layperson is usually not enough to form your own opinions on specific scientific questions. Forming a reliable opinion often requires a level of detailed knowledge that only an expert in the field can obtain. Even experts can be wrong, of course, and since lay opinions are likely to span all possibilities, some are bound to be correct. Experts, however, are far more likely to have an opinion that accurately reflects the evidence and to understand how to incorporate new evidence as it comes in.

Let’s take vaccines as an example. To understand just a part of the science of vaccinations requires research into the fields of immunology, virology, epidemiology, infectious diseases, physiology, and possibly dozens of other areas of the biomedical sciences. It is simply impossible for one person to be an expert across all of those fields.

Thus, to develop just one vaccine, numerous experts, across a large number of biomedical disciplines, are involved. I have tremendous respect for Paul Offit – not only is his knowledge of vaccines based on his own education and research but also on the backs of research from hundreds of other researchers over a century (at least).

Evidence doesn’t come from a few hours on Google. Proper evidence is derived from researchers who spend years looking at small parts of the larger picture. And then there are hundreds or thousands of researchers working on their small part of the picture.

The fact of evolution doesn’t rely upon one article or book – in fact, Charles Darwin forms only one small part of the story of evolution. There are probably hundreds of thousands of published research that builds the story of evolution. Maybe you’ll find an occasional error here or there in the evidence for evolution, but it’s still overwhelmed by all of the other studies.

The same for the other big scientific issues of our time – climate change, GMOs, vaccines, and many others. The scientific consensus for anthropogenic climate change, the safety of GMOs, and the safety and effectiveness of vaccines is huge. These consensuses will not collapse with one error here or there. They will not collapse because some gadfly publishes a contrary article in a minor journal.

If there’s one thing that I wish I could impress upon the science deniers is that cherry picking one or ten articles that seem to contradict the consensus doesn’t do anything. If there is something that will cause the collapse of a scientific consensus, it will be research from many different locations, published in the highest quality journals, over a long period of time.

Because the consensus was formed by research from many different locations, published in the highest quality journals, over a long period of time.


Scientific consensus as appeal to authority

Sometimes, the scientific consensus is criticized as being a logical fallacy – an appeal to authority. However, it’s misused in this case.

Generally, an appeal to authority becomes a logical fallacy when a presumed authority makes an argument outside of the authority’s field of expertise, in a topic in which the authority is biased.

Clearly, one can appeal to authority if the evidence supports the claims of the authority.

For example, a biochemist can be an authority on evolution. In fact, I would expect nothing less. However, there are PhD level biochemists who are creationists – these are false authorities, because they have no or disputed evidence for their claims.

Climate change denialism is filled with false authorities. Over 97% of papers published about climate change support the fact of human caused climate change. If science were actually a democracy, this would be a landslide. Yet, climate change deniers rely upon false authorities and bad research to claim that there’s a “debate.” There’s no debate.

Not only are 97% of published papers in support of climate change, but also those papers are published by leading researchers in dozens of different fields. There are geologists, climatologists, archeologists, paleontologists, meteorologists, physicists, chemists, botanists, and dozens of other fields of science that publish tiny bits of evidence that form the whole of the consensus. Once again, like evolution, the evidence is the size of a literal mountain.

And these authority figures in all of these fields do not suddenly rise to prominence after a couple of hours Google searches. To become a competent immunologist, one of the fields that are basic to vaccine research, It takes years of education and research to understand, let alone describe, the nearly infinite complexity of the immune system.

To understand even the basics of immunology, one needs to grasp complex sciences like biochemistry, cell biology, physiology, and probably a half-dozen other fields of biology.  Understanding the human immune system, an incredibly complex physiological response to the environment, isn’t something that can be grasped in a few hours.

Even after eight years of formal education immunology, it probably takes another decade of research, writing, presentation, criticism, and publication to be declared an expert. But even then, it’s all about the evidence.

There are actual false authorities in immunology, like Tetyana Obukhanych, who, on the surface, appear to be real experts or authorities, but they have no published evidence that supports their public opinions. That’s where the logical fallacy arises.

That’s why, as Dr. Novella states, we rely upon the expert opinion, though as skeptics, we still have to weigh the evidence, even if presented by experts. As I wrote in articles on skepticism and debunking pseudoscience, large amounts of high quality evidence must be used to form a consensus, or, alternatively, shift us away from the consensus. 

What makes the scientific consensus so powerful, ideas that should be respected, is that the conclusions are crowd-sourced from many experts across many disciplines. Moreover, the conclusions are self-correcting as new evidence is provided. Opinions that aren’t included in the consensus rarely get supported not because of some conspiracy, but because the level of evidence has not reached the quality or quantity to be considered.

scientific consensus

Criticisms of the scientific consensus

Generally, there are two broad condemnations of the scientific consensus – science has been wrong before, and corporate influence.

Let’s start with the false flags and tropes that try to claim that science gets it wrong all the time. But that’s just not true. Scientific evidence showed that smoking was harmful, despite the myth that “all” scientists thought that smoking was safe.

“Science” never claimed that world was flat. Or that the universe orbited around the earth. Or that there were canals on Mars. Or that thalidomide was safe. There was never a consensus about any of that, some of them, in fact, were religious beliefs, not scientific ones.

It’s ironic for me to say this, but a scientific consensus is provisional. Forming a consensus is difficult, but it can be overturned – with more and more powerful evidence.

Now, this doesn’t mean aspects of science don’t change over time. For example, I use evolution as an example of a fact – yet it’s constantly being “fine-tuned,” as new information is found. However, evolution itself is probably the most powerful consensus in science.

The second condemnation of the scientific consensus is corporate influence. This belief is so profoundly ridiculous, I find it difficult to even waste a nanosecond in refuting it. Thankfully, Dr. Novella saves me some time in his recent article:

What does the recent study on the climate change issue say about corporate influence? Combining this study with experience in other areas, like evolution, vaccines, and genetically modified organisms, I think we can make some generalizations.

First, it is interesting to note that the oil industry is perhaps the most wealthy and powerful industry of any of the industries involved in the above public debates. They have more resources and influence than Big Pharma, Big Agro, or Big Evolution (whatever that is). It also seems clear that they were actively trying to influence the scientific consensus.

Despite their motivation, influence, and resources they were unable to affect the scientific consensus on climate change. They could not manufacture a consensus. All they could do is sow doubt in the real scientific consensus, and even then only among those ideologically aligned, not with the public at large, and not within scientific circles.

This fact is often given as a direct refutation of the claim that Monsanto and Big Agro have manufactured a scientific consensus on the safety of GMOs. At the same time they argue there is no consensus. First – yes there is. There is an international scientific consensus on the overall safety of GMO technology and the current GMO products.

This consensus is at least as strong, and I would argue stronger, than the consensus on climate change. Biotechnology companies have nowhere near the resources as the fossil fuel industry, and it is frankly absurd to argue that they were somehow able to use their money and influence to manufacture a fake scientific consensus on GMO safety. They would have to have secretly controlled the outcome of hundreds of apparently independent studies. The same is true of vaccine safety.

Is that clear?

Let’s put these in numbers that you can hug and caress. The top 15 “Big Pharma” companies had a total revenue of slightly greater than US$500 billion in 2014. That sounds massive, doesn’t it? Exxon-Mobil has that level of revenue all by itself. And yet, despite a secret policy of climate change denial, it failed miserably to influence the scientific consensus on climate change. Influence from Big Pharma and Big Agra have even a lower chance of having any effect on scientific consensus.

Why is it so difficult for corporations to influence the scientific consensus? It goes back to how the the system works. The consensus is built on evidence, which is repeated over time, it is self correcting, and minority “opinions” (not evidence) lack the standing in the field to overwhelm the actual evidence supporting the consensus.

The scientific consensus is one of the cleanest examples of well-formed crowd sourcing!


Scientific consensus examples

In some cases there are independent scientific groups that proclaim the scientific consensus. The American Association for the Advancement of Sciences is an international non-profit organization that which promotes cooperation among scientists, to defend scientific freedom, encourages scientific responsibility, and supports scientific education and science outreach for the betterment of all humanity. It is the world’s largest and most prestigious general scientific society, and is the publisher of the well-known scientific journal ScienceIt occasionally makes statements on the scientific consensus.

For example, here is the consensus position of the American Association for the Advancement of Sciences on anthropogenic (human-caused) climate change:

The scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society. Accumulating data from across the globe reveal a wide array of effects: rapidly melting glaciers, destabilization of major ice sheets, increases in extreme weather, rising sea level, shifts in species ranges, and more. The pace of change and the evidence of harm have increased markedly over the last five years. The time to control greenhouse gas emissions is now.

The AAAS has also released another statement of consensus science on genetically modified foods (pdf):

The science is quite clear: crop improvement by the modern molecular techniques of biotechnology is safe … The World Health Organization, the American Medical Association, the U.S. National Academy of Sciences, the British Royal Society, and every other respected organization that has examined the evidence has come to the same conclusion: consuming foods containing ingredients derived from GM crops is no riskier than consuming the same foods containing ingredients from crop plants modified by conventional plant improvement techniques.

There’s even a scientific consensus on vaccines, written by the the most prestigious scientific academy in the world, the National Academy of Sciences:

Vaccines offer the promise of protection against a variety of infectious diseases. Despite much media attention and strong opinions from many quarters, vaccines remain one of the greatest tools in the public health arsenal. Certainly, some vaccines result in adverse effects that must be acknowledged. But the latest evidence shows that few adverse effects are caused by the vaccines reviewed in this report.

Despite the prestige of these institutions and the power of the evidence supporting the consensus, there will be a group that picks and chooses what they believe or don’t believe. It’s hysterical.

If you accept the consensus on climate change or evolution, but reject it for GMOs because each fit your pre-conceived view of the world, you are a science denier. Yes, I’m tough about this, because it shows the level of hypocrisy in these individuals.

You don’t get to accept the power of the consensus behind anthropogenic climate change but reject it for GMOs, just because you feel like it. The evidence for both is so huge, so overwhelming, your gut feeling or opinion is completely irrelevant.

I keep finding it ironic that GMO deniers and climate change deniers use the same exact “arguments” to reject science. They accept the pseudoscience that supports their a priori conclusions, while rejecting the science that doesn’t fit. That’s why many many writers agree that GMO deniers are the climate change deniers of the left.

Finding evidence for a scientific consensus

This isn’t easy, but a consensus is not built on magic, debates, or even magical debates. It’s built on high quantity, along with high quality, of evidence.

There is a hierarchy of evidence (see Note 2) from utterly useless (anything in Natural News) to really bad (primary research described in an abstract presented at a scientific meeting as an example) to outstanding.

At the top of the list of scientific research are systematic reviews, which really are the foundation of powerful scientific consensuses. The systematic review examines all of the evidence, attempts to determine which evidence is weaker (based on statistical results and experimental design which might influence the results), and finally assembles it all into one study of studies that is complete and representative of all the research that has been done in one specialized field.

Instead of consciously or unconsciously (or deviously or innocently) choosing the papers that support your point of view, meta-reviews use science on science. They allow us to logically build and support a consensus.

This isn’t easy work (as is everything else in science, which is something that I believe is always ignored by science deniers). Each study ever published in the field must be closely reviewed. Data that might not have been published needs to be tracked down.

Authors of previous research might be contacted to explain information. Then all of the data is assembled into one huge statistical analysis. So instead of a clinical trial containing only 250 or 2500 patients, if you take all the trials ever done, you might have one of hundreds of thousands of patients.

Scientific consensus – collective opinion

When the authors of the systematic analysis assemble all of the data, they find the summary effect. If it is near the line of “no effect”, the researchers can conclude that the analysis shows no effect from a drug.  Above is an example of a systematic analysis in a visual form called a “blobbogram,” although more formally as a Forest plot. Each of the horizontal lines represents an individual study, with the solid dot equal to the mean, and the horizontal line itself the error around the mean. The one vertical line, at 1, is the line of no effect. In this graph, the diamond point is the summary effect, which implies that it this imaginary drug has some effect.

Now, this type of systematic review is specific to clinical medicine. There are, however, large statistical reviews of scientific knowledge in many fields. A recent powerful review article discussed how climate change would effect public health.

One of the best organizations to produce systematic reviews is the Cochrane Collaboration, a non-profit academic organization that has produced meta-reviews of evidence in important questions in medicine for over 30 years. I consider their reviews to be the gold standard of research, though I think they have some tarnish on the gold at some times. A few of their reviews have tended to show strong selection bias of their authors.

Not all systematic reviews are published by Cochrane. There are many other published in major medical and scientific journals which help establish a scientific consensus. And just as one can cherry-pick individual articles, without critical analysis, to support or refute a point of view, one can do the same with these larger reviews.


Summary or TL;DR

  • The scientific consensus is a powerful tool to determine what is scientifically accurate and what is not.
  • The scientific consensus is based on evidence, generally published in high quality peer-reviewed journals. The evidence is repeated across many locations and over a large amount of time.
  • The scientific consensus can be described as a meritocracy, that a consesnus only forms based on the merit of the experts and their evidence.
  • Logic and evidence are the only qualities that matter.
  • A scientific consensus represents the best knowledge of the best experts in a particular field. This is not a logical fallacy of the appeal to false authority, because evidence is always the basis of the consensus.
  • Pointing out past examples of rejected scientific consensus is ridiculous. Most of the “claims” didn’t even represent the scientific consensus of the time. Even more, what is presented as “scientific consensus” were not at the level of scientific knowledge that we have today.

So, let’s be clear.

The scientific consensus says that evolution is a fact.

The scientific consensus says that climate change was caused by humans and will probably be dangerous to the planet.

The scientific consensus says that vaccines are safe and effective.

The scientific consensus says that GMOs are safe.

If you want to reject any of those facts because it hurts your feelings? Get over it.

If you want to reject any of those facts because it contradicts your belief set? You’re simply a science denier, and get over it.

If you want to reject any of those facts because it doesn’t fit your preconceived political view? Time to learn real science.

Editor’s note: This is an updated article that was originally published in December 2013. It has been revised and updated to include more comprehensive information about evidence, to fix some formatting issues, to reduce advertising, and to some new ideas about the scientific consensus.


  1. Thanks to commenter Mike Lewinski for giving me information to add to this section.
  2. I have written several articles on how to distinguish and rank good research from bad. See this article, this article, and if you’re really energetic, this one.

Key citations:


The Original Skeptical Raptor
Chief Executive Officer at SkepticalRaptor
Lifetime lover of science, especially biomedical research. Spent years in academics, business development, research, and traveling the world shilling for Big Pharma. I love sports, mostly college basketball and football, hockey, and baseball. I enjoy great food and intelligent conversation. And a delicious morning coffee!
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  • lifebiomedguru

    It is challenging to define a consensus when a minority of
    scientists write public health policy cite their own research, but ignore the thousands of other studies that do not support their policy. And yes, I mean vaccine induced neurological injuries.

    It would be convenient for that minority (now subject of an
    internal investigation at the CDC) if Pubmed did not exist, and if they
    majority of articles on autism were not open sourced, even by for-profit journals. However, the vast majority of the 2,000 articles published on autism show clearly that aluminum causes hyperactivation of microglial cells in the mammalian brain. Being that humans are mammals, we are not exempt.

    The genetics data overwhelming indicates that de novo mutations
    and inherited mutations can, in a minority of people, break any of a variety of detoxification and synaptic protein pathways…I am not talking voodoo magic or sorcery, I mean well-known, mundane key cellular functions such as properly functioning endoplasmic reticiuli. Combined w/another hit, environmental triggers become causal (necessary and sufficient given the genotype).

    Some of us have read the consensus in the autism research
    literature, and the days of anyone – including Pediatricians – of accepting the black & white “vaccines do not cause autism” are numbered. Even DeStefano has admitted that there may be a subset of people who are genetically susceptible. The position is utterly indefensible if one really looks at all of the publications.

    So I ask again: what do you call incorrect positions formed by
    ignoring that vast published literature that shows risk of neurotoxicity? Surely that’s not *scientific* consensus. I’m sure you’re aware of the fallacy of consensus gentium – merely because everyone believes something at one moment in time in the history of science does not make that something true.

    Anyone who says otherwise, please tell me how you know that
    macrophages do not pick up toxins, including mercury, aluminum, etc and deposit them in the brain (before the blood/brain barrier is formed), how you know that once in situ they do not activate microglial cells, which prune growing nerve cells and can, in a hyperactivated state, induce apoptosis; how do you know
    that cytokine production does not then keep microgial cells in a hyperactivated state, resulting in over-pruning; how you know that these synaptic function failures do not lead to long-range hypoconnectivity, and failure to develop functional specialization, when the consensus in the autism research field is that all of these facts are correct?

    Studies aimed at association and animal studies that look at
    adjuvant dosing in 15 animals are not powered for and effect on 1-2% of the population… and they often use hetergeneous clinical populations (violation of the “Assume x is random variable from a homogeneous population). The data also have been tortured to make associations go away, using innappropriately applied collinear ‘control variables’… so if our ‘consensus’ is based on poorly designed, often underpowered, and evidently fraudulent studies (Thompson), and our ‘consensus’ ignores that fact that (2012 IOM rejected 17/22 studies cited by the CDC showing ‘no association’)… one must question why such a consensus persists.

    From where I sit, with my experience of reading over 1,000 of
    the 2,000 studies on the molecular etiology of autism, it takes faith beyond reason to continue to state, unqualified, that “vaccines do not cause autism”.

    As always, detractors, you are welcome to ignore the salient
    points of my comment, and please, by all means, let the ad hominem attacks begin! It’s really all you have. I’d much rather hear from people who have read the literature, and are not merely bent on having a good time on the internet squashing people interested in the facts on vaccine safety research. Efficacy is another issue. And this goes way beyond MMR. Who’s first?

    • Sandy Perlmutter

      Bibliography/references supporting your point of view?

    • Apparently you failed to actually read the article. Respected institutions, not biased bullshit research like you quote, have determined that the vast bulk of research says you’re full of shit.

      We’re done here.

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