An article of faith of the modern environmental movement is the scientific “consensus” behind man-made global warming. Global warming activists and even some serious scientific organizations claim that 97% of the world’s scientists unreservedly accept this theory. It is often the first and most common argument used by climate activists, from Al Gore to the Greenpeace climate warriors protesting in front of the White House.
Pope Francis incorporated this belief into his 2015 “green” encyclical, Laudato si’: “A very solid scientific consensus indicates that we are presently witnessing a disturbing warming of the climatic system.”1 He repeated it during an airplane interview on September 6, 2017, on the return flight from a trip to Colombia. A reporter asked the Pope if, in light of the recent devastation in the United States caused by Hurricane Harvey, he thought there was a “moral responsibility” for countries to reduce their greenhouse gas emissions.
He agreed entirely, appealing to a “consensus” of scientists:
“…Whoever denies this should go to the scientists and ask them. They speak very clearly. The scientists are precise… you see the effects and scientists say clearly which is the path to follow… [So] if one is a bit doubtful that this is not so true, let them ask the scientists. They are very clear. They are not opinions on the air, they are very clear. And then let them decide, and history will judge their decisions.”2
Bishop Marcelo Sanchez Sorondo, the Pope’s right-hand man for climate activism, stated:
“From the scientific point of view, the sentence that the earth is warmed by human activity is as true as the sentence: The earth is round!”
Is there a “scientific consensus” about man-made global warming? Can there be any such thing as a scientific “consensus” in the first place? Do 97% of scientists believe in global warming?
The answer to all three questions is an unequivocal NO, and we will analyze each one in depth.
What Is a “Scientific Consensus” Anyway?
The word “consensus” is confusing at best and deceptive at worst. There is no infallible “pope” of science who declares one or another scientific theory to be fact and all others to be heretical. Science has relatively few absolute, unchangeable truths and many theories of varying degrees of certitude. A scientific theory is not infallible simply because a democratic majority of scientists say so.
And what is the definition of “scientific consensus?” Different scientific theories are accepted by various numbers of scientists to varying degrees, all of which are labeled “consensus.” If 50% + 1 of scientists accept a theory, does that make a “consensus?” Or does it have to be 75% or more? If so, why?
What about the degree of adherence to a scientific theory? If 90% of scientists believe a theory is “probably correct,” but only 10% affirm that is “certainly correct” (which is the case in many scientific debates) does that make a “consensus?” If so, why?
Most importantly, why is it wrong to question a “scientific consensus” (however one defines it) in the first place? As any honest scientists will admit, in every scientific field, disagreement is common, and widespread “consensus” is the exception. Scientific knowledge is constantly undergoing challenges, upheavals, and paradigm shifts thanks to new discoveries. Indeed, the history of science is littered with the wrecks of refuted theories.
In biology, for example, our knowledge and theories about the cell have changed more from Charles Darwin’s death in 1882 to today than in the previous 10,000 years of human history combined. Astronomy has learned more about the planets, galaxies, and the universe in the twentieth century than in the 1,800 years since Ptolemy.
Scientists continually propose scientific theories that buck mainstream “consensuses.” Even today, we do not have certainty about basic scientific questions such as the size of the universe, the nature or existence of “black holes,” the age of the Earth, or even whether light is a particle or a wave. Our understanding of the atom has undergone numerous transformations over the last 200 years and continues to do so.
Climate science is extremely complex. Every year, we learn more and more about the many factors that influence the Earth’s climate. Scientists can and do make incorrect assumptions or conclusions based on faulty theories or incomplete data. In the seventies and eighties, many scientists, scientific organizations, and most of the media declared a scientific “consensus” that a global cooling trend was underway that would lead to a new Ice Age. Now, some of the very same scientists tell us that anyone who questions global warming is a “denier.” Either the “consensus” was wrong then, or it is wrong now.
Appealing to authority rather than evidence—as proponents of the man-made global warming theory are doing when they claim a “scientific consensus”—is anything but scientific. It is nothing less than an attempt to silence opposition, shut down all debate and scare the general public into submission.
Do 97% of Scientists Endorse the UN’s Position on Global Warming?
To this end, the most common argument used by climate activists such as Al Gore is that 97% of scientists worldwide explicitly endorse the United Nation’s Intergovernmental Panel on Climate Change (IPCC) position that man-made global warming is happening, that it is caused mostly by man’s activities, and that it is a grave threat to humanity and the Earth.
It is quite an intimidating figure. Anyone who dissents from man-made global warming, therefore, must be a member of a tiny, dangerous, isolated fringe. Perhaps they chose the 97% figure because 90% still leaves too large of a minority in opposition, but 99% or 100% is not very believable. At any rate, it is a very well chosen number for psychological effect.
The average observer might think that such a solid number as 97% has equally solid evidence to back it up. In reality, the most commonly cited studies presented to support the “97%” figure are misleading at best, and fraudulent at worst.
We will cite one of the most respected government scientific organizations in the world, NASA. On its web site dedicated to man-made global warming, NASA lists four studies to support its claim that “97 percent or more of actively publishing climate scientists agree: Climate-warming trends over the past century are extremely likely due to human activities.”3
One study cited is “Beyond the Ivory Tower: The Scientific Consensus on Climate Change” by historian Naomi Oreskes. In 2004, Oreskes took 928 papers published in scientific journals from 1993 to 2003 and searched them for evidence of support for global warming. She did not search the whole paper, but rather those papers “abstracts,” which is the summary written at the very beginning of the paper that summarizes its main points. She claimed that 75% of the abstracts either implicitly or explicitly supported the IPCC’s view that humanity is responsible for most of the global increase in temperature for the past fifty years.
Oreskes’s conclusions are flawed for several reasons. First, many of the articles she cites mention global warming only in passing, or assume some human impact on climate. A much smaller number explicitly endorses the IPCC view. Oreskes did not make any distinction and lumped them all together as supporting the IPCC. She also did not make any distinction between authors who believe global warming is dangerous and those who believe it is benign.
Second, she reviewed only the abstracts of the 928 scientific papers for evidence of support for global warming, and not the papers themselves. Abstracts routinely misrepresent the content and conclusions of the papers and are often chock full of keywords for search engine purposes. This is no different than reading the blurb on the back cover of a book and drawing conclusions about the author’s positions on topics other than what he wrote about.
Third, most of the scientific papers are not about climate change, and most of their authors are not specialists in any of the climate sciences. Oreskes also ignores the many hundreds of articles published by prominent climate skeptics that raise serious doubts about man-made global warming.
Fourth, in 2008, medical researcher Klaus-Martin Schulte published a scientific study of the Oreskes report and found that only 7 percent explicitly endorsed the IPCC view on global warming.4
Another scientific paper cited by NASA and widely used to push the 97% myth is by Australian cognitive scientist John Cook. In 2013, he published a paper in Environmental Research Letters in which he analyzed the abstracts of 11,944 published scientific papers, published between 1991 and 2011 that include the words “climate change” or “global warming.” According to his very broad criteria, of all the papers that express an opinion about man-made global warming, 97.1% endorsed the IPCC position that humans are the main cause.
This paper was immediately debunked by a scientific paper published in Science & Education by David Legates, Wei-Hock Soon, William Briggs, and Christopher Monckton, in which they found that, in reality, of all the scientific papers that express an opinion on global warming, only 1% were found to explicitly endorse the IPCC’s position.
Richard Tol, a lead author of the UN’s IPCC reports, flatly rejected Cook’s findings:
“Cook’s sample is not representative. Any conclusion they draw is not about ‘the literature’ but rather about the papers they happened to find. Most of the papers they studied are not about climate change and its causes, but many were taken as evidence nonetheless. Papers on carbon taxes naturally assume that carbon dioxide emissions cause global warming—but assumptions are not conclusions. Cook’s claim of an increasing consensus over time is entirely due to an increase of the number of irrelevant papers that Cook and Co. mistook for evidence.”5
Also cited by NASA is a 2009 study by then-University of Illinois student Maggie Zimmerman and her master’s thesis adviser Peter Doran. But just like the previous two, it also contains serious flaws.
Zimmerman’s “study” consisted of a two-minute online survey sent to 10,257 scientists working at universities and government agencies asking for their opinion about man-made global warming. A total of 3,146 responded. Of these, she eliminated the scientists whose area of expertise—cosmology, physics, meteorology, solar science, etc.—would lead them to think that the Sun might have a major influence on the Earth’s climate. Only about 5% self-identified as climate scientists.
The survey asked two questions: “When compared with pre-1800s levels, do you think that mean global temperatures have generally risen, fallen, or remained relatively constant?” and “Do you think human activity is a significant contributing factor in changing mean global temperatures?” Those questions are ambiguous, since “significant” could mean many different things, and is certainly not the same as the IPCC report which affirms man as the primary factor. The questions also do not ask if such warming is harmful or benign for the planet, an important distinction.6
To get the 97% figure, Zimmerman restricted her criteria only to self-identified “climate scientists” who must have published at least 50% of their peer-reviewed publications in the last five years on the subject of climate change. This is a serious flaw in methodology since she would include a person who published three papers in the past five years if two of them were on climate change, but not another who published 40 papers of which only 19 were on climate change.7
In short, the Zimmerman paper is a seriously flawed study that was widely promoted by the media to push a political agenda, not science. It was designed to produce one and only one result (the 97% myth) which happens to be the party line pushed by climate activist organizations.
Other studies cities by NASA, such as that done by William R. L. Anderegg in 2010, then a student at Stanford University, are just as flawed. Like the others, he scanned the abstracts of hundreds of scientific papers looking for clues of the authors’ positions on global warming. To achieve the “97%” figure, he restricted his definition of “climate scientists” to those who are the “most published,” which happens to be disproportionally populated by a small group of dedicated activist scientists. He removed those scientists who explicitly signed statements against the IPCC position on climate but included those who had not. In his view, silence on the issue meant that those authors accept the extreme position of the IPCC on man-made global warming.8
It is disgraceful that a heretofore respected organization such as NASA would cite such weak and easily refuted studies to sustain its shaky hypothesis on man-made global warming. It is not a fact, but an unproven assertion that 97% of scientists accept unequivocally the IPCC’s position.
There is no scientific consensus on man-made global warming. The only consensus among scientists is that there is no consensus. Rank and file climate scientists simply disagree on how much warming is occurring (if any), the causes of this warming, the role of man’s activities in this warming, whether or not such warming is benign or dangerous to civilization, and what measures mankind should take to address it (if any).
Although the jury is still out on the danger of global warming, a far worse threat to the common good is the cynical promotion of global warming as a fact by people and organizations such as NASA who know better. Much worse is the Vatican, led by Pope Francis, using the full weight and moral authority of the Catholic Church to give such a fraudulent claim legitimacy.
- Pope Francis, Laudato si’, http://w2.vatican.va/content/francesco/en/encyclicals/documents/papa-francesco_20150524_enciclica-laudato-si.html.
- Craig D. Idso, Robert M. Carter, S. Fred Singer, Why Scientists Disagree About Global Warming (Arlington Heights, Illinois: The Heartland Institute, 2016), p. 10-12.
- Ibid, p. 17-18.
- Ibid, p. 14.