Tom Harris’ recent commentaries rife with errors and illogic

If you’re going to attack climate realists for making supposedly illogical arguments, you’d best be sure that your own arguments are logically flawless.

Tom Harris, Executive Director of the International Climate Science Coalition (ICSC)

Tom Harris, Executive Director of the International Climate Science Coalition (ICSC)

For the other posts in this series, click here.

Starting in the middle of December, 2014 and continuing through February, 2015, Tom Harris, Executive Director of the industrial climate disruptionA denying International Climate Science Coalition (ICSC), wrote at least eight nearly identical commentaries that appeared mostly in small local newspapers and websites around the English-speaking world. The stated purpose of the commentaries was to call for scholars and philosophers to engage in the public argument over climate disruption (aka global warming or climate change), and Harris wrote that “philosophers and other intellectuals have an ethical obligation to speak out loudly when they see fundamental errors in thinking.6” As S&R hosts an occasional feature called “Climate Illogic,” we accepted Harris’ invitation and looked through his own commentaries for illogical arguments as well as other issues of concern.

S&R’s review of Harris’ commentaries turned up five separate areas of significant concern. In Part One, S&R showed that Harris’ commentaries were examples of “tone trolling,” where someone decries the tone or tactics of a debate in an attempt to avoid actually debating the arguments presented. Today we show how Harris tries to pollute the public conversation about climate disruption debate with false equivalence and appeals to moderation, how he misunderstands several logical fallacies he accuses climate scientists and/or activists (aka climate realistsC) of committing, and how he is making many of the same illogical arguments that he alleges climate realists are making.

Harris’ false equivalence and appeals to moderation



False equivalence happens when someone claims that two things are equal when they really aren’t. An example of this is the following: “Cats and dogs are both soft, cuddly pets. Therefore there’s no difference between a cat and a dog (adapted from Wikipedia).” While this example is obviously wrong, most examples of false equivalence are not so obvious. For example, Part One showed Harris’ claim that “death threats and other abuses have been experienced by those on both sides of the controversy5” represents a false equivalence. The statement itself is true, but the nature of the death threats made against climate disruption deniersB is sufficiently different from those received by climate realists that claiming both sides get threats is also a distortion.

When threats of violence are made against climate disruption deniers, the threats tend to be aimed at public figures and journalists, people whose jobs include an unfortunate risk of deplorable language from time to time. The threats directed at climate disruption deniers also tend to be calls for prosecution, which inherently involve due process under the law. And historically left-wing political violence has been directed against property and corporations rather than against individuals.

In contrast, when threats of violence are made against climate realists, the threats tend to be aimed at scientists and private citizens, people who have no reason to expect that they might receive threats as part of the normal course of their lives. The threats also tend to be direct and personal rather than via the judicial system. And historically, right-wing political violence tends to target individuals rather than institutions, making threats against climate realists more credible and thus more intimidating than similar threats by leftists against climate disruption deniers. The fact that both climate disruption deniers and climate realists have received threats cannot be considered equivalent since the typical threats made against climate realists are significantly more threatening than those made against climate disruption deniers.

In his commentaries, Harris wrote that he wants an “open debate on climate,2” one that involves “well-informed opinion from specialists on all sides of the issue (emphasis added).2” Putting aside the issue of “well-informed” expertise for the moment (we’ll get to that in Part Four), what are the “all sides” that Harris refers to? When it comes to the scientific questions about industrial climate disruption, the most important questions don’t have more than two sides, and there’s no balanced middle ground to speak of, and the two sides are “fact” and “fiction.” The following list details some of the climate-related scientific questions that have no middle ground between fact and fiction:

False balance (schoolofthinking.org)

False balance (schoolofthinking.org)

  • Is the Earth’s average temperature increasing? Yes
  • Do we know this beyond the margin of error of the measurements? Yes
  • Is carbon dioxide (CO2) a greenhouse gas? Yes
  • Is the sun the dominant driver of the climate change that’s been recently observed? No
  • Are the increases in atmospheric CO2 from the burning of fossil fuels? Yes
  • Do we understand the mechanism of how the greenhouse effect works? Yes
  • Is the observed ocean acidification is due to the burning of greenhouse gases by human industry? Yes

There are, of course, important scientific questions that are not strictly binary. “How bad will climate disruption be” is arguably one of the most important. But on questions like those above, there are right and wrong answers to which there is no middle ground. Implying that there is a middle ground between fact and fiction is a logical fallacy known as an “appeal to moderation” or the “middle ground fallacy.”

The reason we know the answers to the questions above is because there no longer is any credible scientific debate on those subjects, much as there is no longer any credible scientific debate on whether smoking causes lung cancer. The debate about the existence and causes of climate disruption has been conducted in the peer-reviewed scientific literature over the last 50 or 60 years. According to a 2010 paper by Shwed and Bearman, the publication record indicates that climate scientists had reached a consensus on the subject – that climate disruption was actually happening and that burning fossil fuels was the main driver of it – in about 1991. At this point scientists are as certain about the reality of industrial climate disruption as they are about the connection between smoking and lung cancer.

There are many open climate questions that are still being debated in the peer-reviewed literature. But the existence and dominant drivers of global warming are not among them. Harris’ commentaries imply that CO2-driven climate disruption is still open to credible debate and that there’s a significant chance that the answers to the questions listed above are wrong. He’s incorrect, and the fact that Harris is making these implications means that he’s either ignorant of the facts or in denial of them.

The word “denier” does not mean what Harris thinks it means

CATEGORY: WordsMatterIgnorance is not a crime. No-one knows everything, and as such it’s completely reasonable that some people may not realize just how much we know about the Earth’s climate and why it’s changing. However, some people are aware that the scientific case for industrial climate disruption is overwhelming and yet still deny that it is real. These people are regularly identified in the media, and here at S&R, as being “deniers” of industrial climate disruption.

Harris, a denier of industrial climate disruption himself, doesn’t like the term. He considers it “an attempt to equate those who question climate change causes to Holocaust deniers.2” S&R investigated this specific complaint in a Words Matter post and found that, as of January 2013 (when the post was written) the term “denier” was overwhelmingly linked to denying the reality of industrial climate disruption. In a Google search (with personalized results turned off), S&R found that

  • Links to definitions of “denier” were ranked #1, #6, and #17.
  • The Wikipedia disambiguation page was ranked #2.
  • A reference to the French denier coin came in at #27 and a reference to the denier as a unit of fiber measurement came in at #33.
  • The first Holocaust denial link was ranked #56, on page 6 of the results.
  • The first mention of Holocaust denial was in the “Searches related to deniers” options at the bottom of the first page. The alternate search terms were “deniers definition,” “evolution deniers,” “climate change deniers,” “climate deniers,” “aids deniers,” “famous Holocaust deniers,” “Holocaust deniers claims,” and “Jewish Holocaust deniers.”

Every other link up to #56 was to a website or blog post or news article related to the denial of industrial climate disruption.

While there are certainly people who intend to invoke the spectre of Holocaust denial when using the term “denier,” the word has lost whatever implications it might have once had due to its extensive use with respect to climate disruption.

Harris wants philosophers and experts in logic to respond to the “denier” label by saying that the word is “an ‘ad hominem’ logical fallacy—‘against the man,’ instead of engaging the idea.2” Unfortunately for Harris, experts in logic would not say this for a very simple reason – very few people who use the term “denier” are actually committing an ad hominem fallacy. Calling someone a denier may well be considered insulting, but an insult is not a logical fallacy. Only in the case where someone dismisses a climate disruption denier’s arguments with a “Well, you’re a denier, so of course you’d say that” (or something similar) does the term “denier” become fallacious.

Harris’ misunderstanding of the ad hominem fallacy is quite common – many people falsely equate insults with the ad hominem fallacy. That doesn’t excuse Harris’ misunderstanding, however, especially in commentaries that are superficially focused on cleaning up illogical arguments. Unfortunately, Harris misidentifies a number of other fallacies in his commentaries and he commits several of his own as well.

Correlation, causation and related logical errors

Fingerprints of human influence on the Earth's climate (Skeptical Science)

Fingerprints of human influence on the Earth’s climate (Skeptical Science)

Harris spends a several paragraphs in each of his commentaries detailing how “climate campaigners” or “activists” are allegedly committing a logical fallacy called affirming the consequent. And unlike his ad hominem mistake, Harris actually describes this one correctly. Specifically, affirming the consequent is a cause and effect error like the following:

When the sun is up, the kitchen is brightly lit. The kitchen is brightly lit, therefore the sun is up.

The fallacy is that there are conditions when the kitchen is brightly lit, but the sun doesn’t have to be up – such as after dark when the lights in the kitchen are on.

Harris incorrectly asserts that climate realists are making an illogical argument whenever they say that global warming theory explains why increasing CO2 drives up global temperature. Harris is wrong because scores of peer-reviewed attribution and fingerprint studies have concluded that only a single theory that matches all the data. Specifically, the observed pattern of global warming is best explained by CO2 emissions from human activity in combination with several natural sources of shorter-term variation (solar cycles, El Nino, and volcanic eruptions being the most significant natural drivers).

Harris has been writing about climate disruption for years, so it’s very unlikely that he is unaware that the extensive publication record attributes climate disruption to human activity. Assuming he is aware of the attribution studies, then his claim that climate realists are committing this logical fallacy is disingenuous and/or a logical fallacy of its own – namely the straw man fallacy. After all, it’s easier to attack climate realists for something that they’re not actually doing than it is to attack them for accurately describing the present state of climate science.

Harris implies that climate realists are committing other logical fallacies too. In his defense of the climate disruption deniers who attended the Heartland Institute’s International Conference on Climate Change (ICCC) in Las Vegas, he writes that deniers “dare [to] disagree with fashionable views about climate change (emphasis added).4” By referring to climate disruption at “fashionable,” Harris is suggesting that climate realists are hopping on a scientific bandwagon instead of being convinced by the overwhelming scientific evidence that industrial climate disruption is real. S&R has investigated this particular claim as part of our Climate Illogic series and found that, when an overwhelming number of experts agree on a point because of the evidence, it’s not a bandwagon – it’s a scientific consensus.

Those who live in glass houses….

In one of his commentaries Harris goes so far as to list a number of fallacies that climate realists supposedly make on a regular basis. He writes that

[m]otive intent and ad hominem fallacies are only two of the many logical errors philosophers should explain are poisoning the climate debate. Campaigners regularly use guilt by association, straw man arguments, and appeals to emotion, authority, and consensus to divert the public from considering skeptics arguments.

“Motive intent” is when someone’s motives are questioned because they have a vested interest in the outcome, and it’s one type of ad hominem fallacy. While there is no question that this particular fallacy is rampant in climate discussions, it’s hardly just climate realists (“campaigners,” according to Harris) who accuse climate disruption deniers of having vested interests. Every time an academic or government scientist is accused of being in the government’s pocket because they accept federal grants, the scientists’ motives are questioned. Harris himself has done this as recently as January 8, 2015 – at the same time he was writing these commentaries decrying the tone and fallacies used by climate realists:

In fact, none of the surveys [showing a ~97% consensus among experts that climate disruption is real and human driven] that are used to back up the consensus argument are convincing. They either asked the wrong questions, asked the wrong people, or polled mostly those who would agree with the government’s position. (emphasis added)

Harris’ allegation of “guilt by association” is no different. Michael Mann is presently suing several individuals and organizations who deny the reality of climate disruption for defamation as a result of their falsely associating him with convicted pedophile Jerry Sandusky. And it’s hard to take Harris’ complaints about straw man arguments seriously given his own commentaries include straw man arguments.

As for the “appeal to consensus,” that’s simply another term for the “bandwagon” fallacy. Harris’ “appeal to authority” complaint is yet another common mistake – it’s not a fallacy if you’re appealing to an authentic authority, only if you’re appealing to a misleading authority. S&R’s Climate Illogic post on this very topic pointed out that there are situations where relying on the authority of others is not only logical, it’s both necessary and appropriate.

Harris’s commentaries on the alleged logical failings in the public discussion about climate disruption are themselves filled with errors and logical flaws. He draws false equivalence between death threats made against climate disruption deniers and climate realists. He tries to create a middle ground on aspects of climate science for which fact and fiction are well defined. He misidentifies both the “argument from authority” and ad hominem fallacies. He misrepresents the state of climate science as a way to create a straw man, and then attacks others for supposedly creating straw men of their own. And he implies that climate realists only accept the reality of industrial climate disruption because it’s “fashionable,” rather than because of the overwhelming scientific evidence.

If Harris wants philosophers to wade into an argument that he thinks is awash with illogical arguments, he should make sure his own writing is logical first.

Beyond his logical fallacies and tone trolling, however, in Part Three we’ll see how Harris equivocates on scientific truth vs transcendent Truth, equates ignorance with knowledge, and distorts the ability of science to make unequivocal statements.


  1. TOM HARRIS: Taming the climate debate, posted December 6, 2014.
  2. Climate Debate Needs Philosophers’ Unbiased Insights, posted December 9, 2014.
  3. Guest Opinion: Intellectuals should heal, not fuel, toxic climate debate, posted December 10, 2014. NOTE: this guest opinion is identical to source #1 above.
  4. Taming the climate debate – Tom Harris, posted December 11, 2014. NOTE: this letter to the editor is identical to source #1 except for a number of criticisms of David Suzuki.
  5. We need wise men to defang climate debate
  6. My View: Scholars needed for climate debate, posted on January 7, 2015.
  7. Commentary: Philosophers must tame global warming debate, posted on January 13, 2015.
  8. When Will Intellectuals Heal Toxic Climate Change Debate?, posted on February 7, 2015.


  1. Industrial climate disruption: the position that climate is changing, that the emission of greenhouse gases by human industry is the dominant driver of those changes, and that the changes will almost certainly be disruptive to human society and global ecology
  2. Climate disruption denier: someone who denies that industrial climate disruption is supported by multiple independent lines of evidence and is derived from well established physical laws
  3. Climate realist: someone who accepts the overwhelming data demonstrating that industrial climate disruption is real

5 replies »

  1. Harris may correctly have described the fallacy of affirming the consequent, but perhaps you have omitted the simplest logical challenge to his claim that scientists are committing that fallacy.

    He claims, to borrow your example, that scientists say their theory that the sun is shining is proved because they checked the kitchen and found it to be bright. However, what scientists actually do is to try and negate the expected consequences of a theory in order to disprove it, which is no logical fallacy at all. It is only when all attempts to explain any predicted consequences by other means have been exhausted that a hypothesis is elevated to the status of theory.

    Harris claims that scientists are arguing:

    If A then B
    therefore A

    which would indeed be the fallacy he mentions. But in fact they argue:

    If A then B
    not B
    therefore not A

    or in other words

    If A was the cause of the earth’s greater than expected warming then we’d see effect B
    We don’t see B
    Therefore A isn’t the cause

    which is correct. Harris simply doesn’t understand, or for the purposes of his argument pretends he doesn’t understand, how science is done.

  2. I’ll note, somewhat facetiously, that if there really were a conflation of “climate-science denier” with “Holocaust denier” operating, we should expect to find Holocaust deniers complaining of being equated with climate-science deniers. Such complaints, however, are notable for their absence.

  3. Brian, youi’ve destroyed your own case. Read the latest IPCC report. It says there was no warming trend over the fifteen years 1998 to when the report was drafted in 2012. No warming and lots of CO2 in the atmosphere and lots more added. You’ve really set youself up for a fall if you still think that there’s concrete evidence that CO2 is a major tempeature driver. Not even the IPCC can show that. Sure it *claims* that to be true but it uses climate models to figure it out and the latest report shows that 97% of climate models wrongly predicted warming, so how can anyone take their output seriously?

    But then you also didn’t do yourself any favours by suggesting that scientific truths are determined by the level of support for an idea. Anyone with any knowledge of science knows that. I can see what you’re trying to do but you’re really making a mess of it.

    • First, let’s not cherry-pick endpoints like 1998. When the full dataset is considered, there is a great deal of statistical correlation between CO2 and temperature. Correlation doesn’t prove causation, but neither does lack of correlation since 1998 disprove causation. It simply means that something else has affected the global temperature more than CO2 in the last 15 years and is masking the influence of CO2. And this is what the IPCC AR5 WG1 found – that internal variability is the most likely cause. And let’s not forget that the data has lots of possible flats or even declines – that’s the whole point of the escalator graph:

      Also, allow me to refer you to Tamino’s post about the 2014 data and the fact that we’re actually still totally within the 95% confidence interval. And if you prefer your science peer-reviewed, here’s Foster & Rahmstorf 2011, which shows that, once internal variability has been removed, the trend is proceeding apace. And Risbey et al 2014. And Trenberth and Fasullo 2013. And a host of others as well.

      As far as the supposed wrongness of models, so far as I can tell that claim is based on a non-peer reviewed graph by Roy Spencer, and the graph has been shown to be an artifact of improper baselining. Essentially, Spencer chose a baseline that falsely shows the models are out of step with the data. And Spencer has a history of shopping around for naive journals and editors and pushing pal review for dodgy papers.

      Finally, I didn’t claim that scientific truth is determined by the level of support. It’s determined by evidence. But evidence can lead to a very large level of support, and when it does, we’d be fools to ignore it.