Tom Harris distorts the maturity of global warming science and imagines expertise where little exists

The science supporting global warming theory has a history going back almost 200 years, but readers of Tom Harris commentaries might come away thinking that it’s all brand new science.

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 discussion about 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” S&R’s analysis found that Harris’ commentaries contained multiple examples of the very logical fallacies he was taking others to task for as well as disingenuous arguments and rhetorical boobytraps, all in an attempt to convince readers that the science of climate disruption is less certain than it actually is.

In Parts One through Three, S&R showed how Harris’ commentaries were filled with hypocrisy, illogical arguments, and misinformation and how he was making the bizarre and irrational argument that ignorance and inexperience should be considered equal to knowledge and expertise. Today S&R corrects Harris’ many misunderstandings about the present state of climate science and what makes someone a climate expert.

Global warming is a scientific theory, not a hypothesis

In his commentaries, Harris refers to climate disruption as the “dangerous human-caused global warming hypothesis1.” This is an attempt by Harris to belittle global warming theory by making it seem to be less well understood than it actually is. To understand how let’s start with the scientific definitions of both “hypothesis” and “theory.”

2 : a tentative assumption made in order to draw out and test its logical or empirical consequences (Merriam-Webster)
A tentative statement about the natural world leading to deductions that can be tested. If the deductions are verified, it becomes more probable that the hypothesis is correct. If the deductions are incorrect, the original hypothesis can be abandoned or modified. Hypotheses can be used to build more complex inferences and explanations. (National Academies of Science)
5 : a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena (Merriam-Webster)
In science, a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses. (National Academies of Science)
Milankovich cycles (Scott Rutherford)

Milankovich cycles (Scott Rutherford)

Global warming theory is comprised of many individual hypotheses. For example, scientists originally thought that the Sun was the dominant factor driving climate changes. Given life wouldn’t exist on the Earth without the sun, it’s a reasonable hypothesis. But then scientists discovered that the last million or so years of ice ages split up by warmer periods (aka interglacials) didn’t really follow any known solar processes. Instead, the cycles matched gradual changes in the Earth’s orbit (Milankovitch cycles). So scientists formulated a new hypothesis that Milankovitch cycles could be the cause of recent global warming. But when they looked closely at the Earth’s position in a cycle, they found that the Earth should be cooling at this point, not warming, so clearly that hypothesis wasn’t right either. Something else was overwhelming the natural Milankovich cycles. And so scientists formulated new hypotheses to test every other plausible (volcanoes, human burning of fossil fuels) and several not-so-plausible (galactic cosmic rays, geothermal heating from the Earth’s core) cause for the observed global temperature rise.

Anthropogenic vs. natural radiative forcing (IPCC AR5 WG1 Figure TS.6)

Anthropogenic vs. natural radiative forcing (IPCC AR5 WG1 Figure TS.6)

Last year the Intergovernmental Panel on Climate Change published the latest and best understanding of what actually drives climate disruption, pictured at right. This figure shows that, while carbon dioxide (CO2) is the dominant human effect, methane (CH4), ozone (O3), halocarbon refrigerants and propellants, carbon monoxide (CO), and even dust and soot also have significant effects on the global climate. Clearly, scientists are well past the “hypothesis” stage and well into the “theory” stage with respect to the causes of global warming.

In fact, scientific understanding of each of the following areas is sufficiently advanced that none of them can be legitimately considered hypotheses any more:

Given that all these hypotheses have been tested and are well established in the peer-reviewed scientific literature, and since they’re all connected to global warming theory, it’s clearly not accurate to call global warming a mere “hypothesis.”

Global warming theory is not a “rapidly evolving field”

Jean-Baptise Joseph Fourier (Wikipedia)

Jean-Baptise Joseph Fourier (Wikipedia)

Harris also mischaracterizes climate disruption as a “complex, rapidly evolving field.2” The reality is that scientists have known that something had to be keeping the Earth from freezing solid (now known as the greenhouse effect) since Joseph Fourier proposed the idea in the 1820s. S&R recommends that readers interested in the details read “The Discovery of Global Warming,” exhaustively researched by Spencer Weart and maintained online by the American Institute of Physics. What follows is a summary of the critical discoveries made over the last 200 years that have led to our modern understanding of climate disruption.

Scientists have known that CO2 and water vapor are greenhouse gases since 1859 when John Tyndall demonstrated it via laboratory experiments. In the 1890s Svante Arrhenius made the first crude (by modern standards) calculations showing that CO2 changes in the atmosphere could drive global temperatures up and down and he published a book on this and related subjects in 1908. In 1952, Lewis D. Kaplan discovered that adding CO2 to the top of the atmosphere would change how the Earth emitted heat it had absorbed from the sun, and in 1956 an early model of the Earth’s atmosphere created by physicist Gilbert N. Plass showed that the Earth’s surface would warm by 3-4 °C for a doubling of CO2. And in 1955, chemist Hans Suess discovered that the CO2 in the atmosphere was coming from burning fossil fuels.

Scientists have been accurately measuring the amount of CO2 in the atmosphere since Charles Keeling started making regular, high accuracy measurements above Mauna Loa, Hawaii, in 1959. Two Princeton computer scientists (Syukuro Manabe and Richard T. Wetherald) built one of the first climate models that accurately produced climate features (temperate zones, deserts, etc.) on a simulated planet, and when they doubled CO2, the temperature of their simulated planet increased by about 2 °C – in 1967. Chlorofluorocarbons (CFCs) were identified as significant greenhouse gases by Veerabhadran Ramanathan in 1975, and methane and NO2 were similarly identified in 1976. And this is just the science of greenhouse gases. There are similar histories stretching back decades regarding the effects of aerosols like smog and volcanic ash, black carbon like soot from cooking fires, and clouds.

Of course, climate scientists don’t know everything. Clouds are still a complicated and confounding subject. There are some areas of climate disruption where the science is evolving rapidly. But just because scientists are making regular discoveries about how clouds work doesn’t mean that climate science in general is “rapidly evolving.” First, that’s a logical fallacy known as “composition,” where attributes of a small part of something are applied to the whole. It’s like Harris is saying “The first M&M I pulled from this bag of M&Ms is orange, therefore all the M&Ms are orange” – it’s completely illogical.

Second, even if scientists are lacking knowledge about one area of a theory doesn’t mean that they’re lacking knowledge about other aspects of the theory. That would be like saying “you don’t know to operate your car stereo, so you probably don’t know how to operate your turn signal either.”

Actual fingerprint of greenhouse gas-caused global warming (RealClimate/Skeptical Science)

Actual fingerprint of greenhouse gas-caused global warming (RealClimate/Skeptical Science)

Occam’s Razor, as it’s applied in science, states that the simplest explanation that fits all the facts is the most likely explanation. With respect to climate disruption, the simplest explanation that fits all the facts is that the Earth is heating up because greenhouse gases emitted by human industry are enhancing the greenhouse effect. Solar heating can’t explain why the stratosphere has cooled while the troposphere has warmed (compare TLT vs TLS trends at the link) – but this is expected from greenhouse gas-driven warming. There’s no physical mechanism for direct geologic heat from the Earth’s core to get enough energy through the Earth’s crust to cause the observed warming, and it also doesn’t explain the atmospheric fingerprint. The CO2 in the atmosphere has the wrong isotopic signature to be coming from the mid-ocean ridges and volcanic eruptions. Galactic cosmic rays (GCRs) do not, as yet, have a physical mechanism by which they can seed cloud formation, and even if one is discovered there’s still the fact that there is no significant correlation between GCRs and global temperature variations.

Global warming theory is the only theory we have that that matches all the facts. No alternative theory even comes close.

Real vs. imaginary expertise

Global warming theory is complicated. To have a good understanding of the subject requires knowledge of physics (atmospheric, particle and quantum), chemistry (atmospheric, geochemistry, and oceanic), biology (ecology, forestry, microbiology, marine biology), geology (oceanography, volcanology), and more. As such, climate science is not so much a single field of study as an interdisciplinary collection of expertise. It takes years, perhaps even decades, to acquire the necessary expertise to speak authoritatively on the subject. Yet Harris wants the scientific debate about climate disruption moved out of the peer-reviewed scientific literature and into the public domain where, he claims, “opinion leaders2” and “specialists on all sides of the issue2” including “leaders in science, engineering, economics, and public policy1” can participate.

What expertise, exactly, do “opinion leaders” bring to the interrelated scientific fields of global warming theory? There are precious few commentators or politicians who have the necessary scientific background to understand climate science, never mind having well-informed opinions. There are scientists who study marine biology or atmospheric physics who lack the expertise to have well-informed opinions on climate disruption because their specialties don’t directly involve the Earth’s climate. It’s therefore unrealistic to think that an engineer or an economist or a scientist involved in some unrelated field of study (say, lunar geology) can contribute meaningfully to a public debate on the science of global warming. There are exceptions, but anyone claiming to be an exception needs to demonstrate their expertise before they should be taken seriously. And until someone has demonstrated that they have the necessary understanding of climate science, they shouldn’t participate in any scientific debate.

Anderegg et al 2010 Figure 1 (PNAS)

Anderegg et al 2010 Figure 1 (PNAS)

A study published in 2010 looked in part at the relative level of expertise among people who participated in open letters and similar position statements. Expert credibility in climate change by Anderegg, Prall, Harold, and Schneider (Anderegg et al 2010) found that climate experts overwhelmingly agreed that industrial climate disruption was real and caused by human industry, and the greater the level of expertise (as measured by peer-reviewed papers), the greater the agreement. S&R asked the study’s authors if the data could be analyzed for an estimate of the relative level of expertise of both scientists who are convinced by the evidence and those who are not. The results were striking (although not peer-reviewed):

Mean number of climate papers
Convinced scientists: 107.5
Unconvinced scientists: 14.2
Scientists with 50 or more climate papers
Convinced scientists: 68.2%
Unconvinced scientists: 7.0%
Scientists with 10 or fewer climate papers
Convinced scientists: 3.7%
Unconvinced scientists: 79.2%
Scientists with zero climate papers
Convinced scientists: 0.6%
Unconvinced scientists: 35.8%

By the most important measurement of expertise – peer-reviewed publications – unconvinced scientists have much less expertise than convinced scientists do. Simply put, the overwhelming majority of actual experts agree that climate disruption is real and caused by human activity. And they’ve reached this conclusion because it’s the only rational conclusion given the data.

At this point the scientific debate about the reality of climate disruption is essentially over. Climate science is as mature as the science that shows smoking causes lung cancer and DDT is bad for birds. There remains some debate about how bad things will get, but ultimately humanity gets to make that choice, just as we did with acid rain and CFCs vis-a-vis the ozone hole.. If we do nothing, the effects of climate disruption will be wide-ranging and generally terrible. If we take action, the effects will be less widespread and less dire.

If Harris wants to have a public policy debate about the best policies to address climate disruption, how much we should spend today to save future generations, and the like, then that’s a completely appropriate public debate to have. And that debate should include engineers, opinion leaders, economists, and others who have a vested interest in the outcomes. Unfortunately, Harris’ commentaries contain so many misrepresentations of the science and attacks on scientists and climate experts that it’s clear he wants more than a policy debate.

The evidence to date suggests that Harris wants to derail the scientific debate as much as he can to raise questions about climate scientists’ objectivity and to poison the well against anyone who does enter into the debate as a result of his commentaries. S&R will go into greater detail about these points in Part Five.


  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

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