Patrick Moore's Carbon Dioxide Denial Debunked

Carbon dioxide levels are their highest in at least 14 million years — that’s the finding of the most complete reconstruction of paleo-CO2 ever assembled, and it means we’re on our way to matching Pliocene-era levels of roughly 3 million years ago, when giant camels roamed the Earth and sea levels stood about 30 feet higher than they do today. 

There is an undeniable correlation between carbon dioxide and climate change today and in other eras, but to understand the relationship between global temperatures and CO2 in the distant past, you have to learn about paleoclimatology, and what other factors contributed to temperatures during those times.

This article from Skeptical Science provides answers about high levels of CO2 in the past, written by real climate scientists, with actual research cited.

This speech by Richard Alley explains how Earth’s climate changed in the past, including the role of CO2.

It’s important to understand that Patrick Moore’s downplaying of the role of CO2 in controlling temperature is contrary to the scientific consensus. It's essential to rely on the collective expertise of the scientific community and the body of peer-reviewed research when assessing the impact of carbon dioxide on global temperature. The prevailing scientific evidence supports the theory that carbon dioxide is a significant driver of global temperature changes, and today it is the undeniable primary driver of global temperatures.

The Rate of Change Is the Point Moore Keeps Missing

Moore's entire chapter rests on comparing carbon dioxide levels across geologic time as if the raw level is all that matters. It isn't. What matters just as much is how fast that level changes, because oceans, ice sheets, and ecosystems can adapt to slow change in ways they cannot adapt to fast change.

In late 2023, a team of more than 80 researchers from 16 countries, led by paleoclimatologist Bärbel Hönisch at Columbia University's Lamont-Doherty Earth Observatory, published the most complete reconstruction of atmospheric CO2 ever assembled, spanning the last 66 million years. Their findings undercut Moore's argument rather than support it: the last time CO2 was consistently as high as today's roughly 420 parts per million was about 14 million years ago. The hottest stretch in that entire 66-million-year record was the early Eocene, roughly 50 million years ago, when CO2 spiked to about 1,600 ppm and global temperatures ran as much as 12°C (21.6°F) warmer than today.

Yes, that's a higher CO2 level than today — exactly the kind of data point Moore likes to wave around. But he leaves out the part that actually matters: that Eocene spike unfolded over hundreds of thousands of years, giving oceans, ice sheets, and ecosystems time to adjust. The increase we've caused since the Industrial Revolution, from about 280 ppm to over 420 ppm, has happened in roughly 150 years. There is no comparable rate of change anywhere else in that 66-million-year record. Moore's chapter never mentions rate, only level, because the rate is what collapses his argument.

His "Clincher" Comes From a Gold-Investment Blogger, Not the Study That Actually Settled It

Moore doesn't just gesture vaguely at the ice-core CO2 lag. He presents it as his chapter's decisive piece of evidence, built around a chart showing carbon dioxide rising roughly 800 years after temperature in Antarctic ice cores. If temperature moved first, the logic goes, CO2 can't be in charge. He calls it a clincher. His source for that chart is Joanne Nova's blog.

Here's what he doesn't tell you about that source. Joanne Nova holds a bachelor's degree in microbiology and molecular biology and a graduate certificate in science communication. She has no climate research background. Her self-published "Skeptics Handbook" was distributed in the United States by the Heartland Institute, a think tank built to manufacture doubt about climate science, and she also runs a gold-investment advisory business on the side. That's the source Moore reached for instead of the actual scientific literature on ice-core lags.

And that literature had already answered his exact question nearly a decade before his book came out. Shakun et al., published in Nature in 2012, assembled 80 global temperature proxy records spanning the last deglaciation. Averaged across the planet, they found CO2 began rising before temperature over most of the record, and that roughly 93 percent of the total warming coming out of the last ice age happened after CO2 started climbing, not before. The 800-year lag on Nova's chart describes a regional pattern at the very start of the sequence in the Southern Hemisphere. It is not the global relationship between CO2 and warming, which runs the opposite direction from what a single blog chart makes it look like.

Orbital cycles in Earth's tilt and orbit — Milankovitch cycles — are what actually trigger the initial warming at the end of an ice age, by changing how much summer sunlight reaches high-latitude ice sheets. That warming releases CO2 that had been locked in the oceans, and the released CO2 then does most of the work amplifying and prolonging the warming for thousands of years afterward. That mechanism is also the opposite of what's happening today. We are not waiting on an orbital nudge to slowly release CO2 from the ocean over centuries. Humans are injecting carbon directly into the atmosphere by burning fossil fuels, at a pace with no precedent anywhere in the ice-core record. We are the ignition source now, not the amplifier arriving late.

Why a Fainter Sun Makes Moore's Comparison Meaningless

There's a deeper problem with lifting a CO2 number out of the Eocene or some other distant epoch and setting it next to today's number as if the two are directly comparable: the sun itself was different.

Stars brighten gradually as they age. Going back just 50 million years, to that hot Eocene spike Moore's own logic depends on, the sun was putting out slightly less energy than it does now. Go back further, into the hundreds of millions to billions of years, and the effect becomes dramatic: during the Archean eon, the sun was roughly 30% fainter than today, an effect well-documented enough in astronomy to have its own name, the "faint young sun paradox." A fainter sun changes how much warming a given level of CO2 actually produces at Earth's surface. It's one of several variables, alongside continental position, ocean circulation, and vegetation cover, that shaped ancient climates. Comparing a raw CO2 number across tens of millions of years while ignoring the brightness of the sun that was heating the planet at the time isn't paleoclimatology. It's cherry-picking one variable out of a system that has several.

NASA's Own "Control Knob" Paper Says the Opposite of What He Claims

Moore also treats the phrase "CO2 is the control knob for Earth's temperature" as an alarmist talking point worth mocking in this chapter. He didn't invent that mockery, and neither did Al Gore. That phrase is the title of a real peer-reviewed paper: Lacis et al., "Atmospheric CO2: Principal Control Knob Governing Earth's Temperature," published in Science in 2010 by researchers at NASA's Goddard Institute for Space Studies.

That paper's actual finding is about as far from Moore's chapter as it gets. It concludes that CO2 supplies roughly 80 percent of the warming effect from Earth's non-condensing greenhouse gases, and that this is what sets the temperature stage that water vapor and clouds then amplify as fast-acting feedbacks. In the study's own model experiment, stripping CO2 and the other non-condensing gases out of the atmosphere collapsed global temperature by nearly 35°C (63°F) within 50 years. Moore cites NASA's own framing, or at least mocks its famous phrase, to wave away CO2's role. The paper behind that phrase is the reason scientists use it in the first place.

A "97 Percent Consensus Disproven" — By a Blog Post, Not Research

Elsewhere in the chapter, Moore claims the well-known "97 percent of climate scientists agree" figure has been disproven, citing a climate-skeptic blog rather than any peer-reviewed rebuttal. It hasn't been disproven. If anything, it was an undercount.

The most rigorous follow-up came in 2021, when Mark Lynas and colleagues published a study in Environmental Research Letters examining 88,125 climate-related papers published between 2012 and 2020. Using an algorithm built specifically to hunt for skeptical arguments — searching for terms like "solar," "cosmic rays," and "natural cycles" — they found only 28 papers, mostly in minor journals, that rejected the human role in climate change out of the entire sample. Consensus among papers that took a position: north of 99.9 percent. "We are virtually certain that the consensus is well over 99% now and that it's pretty much case closed for any meaningful public conversation," Lynas said. A blog post claiming otherwise doesn't move that number. It just tells you Moore didn't check.

This Isn't a Vote. Scientists Have Physically Measured CO2 Trapping Heat.

Moore's chapter keeps circling back to the idea that CO2's warming effect is a matter of consensus, opinion, or interpretation — something reasonable people could simply disagree about. That framing skips past the fact that CO2's heat-trapping property isn't a social construct. It has been directly measured, not just modeled.

In 2015, a team led by Daniel Feldman published a study in Nature that used spectroscopic instruments at two sites in the United States to directly measure the infrared radiation CO2 was absorbing and re-emitting back toward Earth's surface, continuously, from 2000 to 2010. They found CO2's radiative forcing at the surface increased by about 0.2 watts per square meter per decade, tracking the roughly 22 parts-per-million rise in atmospheric CO2 over that period almost exactly. "We see, for the first time in the field, the amplification of the greenhouse effect because there's more CO2 in the atmosphere to absorb what the Earth emits," Feldman said. That's an instrument reading, taken outdoors, over ten years. It doesn't care what percentage of scientists agree with it.

Moore's Own Sources Contradict Him

Professor Sean Holman’s excellent debunking of this book digs into the sources Moore used in this very chapter, and the pattern that emerges isn't of a careful skeptic weighing evidence. It's of a writer whose sources, checked directly, say the opposite of what he claims they say.

Moore uses a graph in Chapter 3 meant to show that "CO2 and temperature are out of sync more often than they are in sync." Holman contacted Christopher Scotese, the paleogeologist whose temperature curve underlies that graph, and Scotese told him his own updated chart "clearly shows" CO2 increases correlating with temperature rises — the opposite of the conclusion Moore draws from it.

Moore also cites a 2006 Nature paper by geochemist Mark Pagani to support his position. Read the actual paper, and its conclusion is that Earth's climate is "extremely sensitive" to carbon dioxide — again, the opposite of what Moore claims it shows.

And when Moore asserts that the IPCC hasn't concluded today's climate is changing unusually fast by historical standards, Holman simply quotes the IPCC's own language back at him: "The current rate of global climate change is much more rapid and very unusual in the context" of the past million years.

The same chapter leans on one more source worth naming. For his claim that no meaningful statistical link exists between CO2 and the Central England temperature record since 1950, Moore cites a report from the CO2 Coalition. That's not a neutral third party weighing in. It's the organization Moore has chaired since 2019, and whose funding and mission we cover in detail on our page about Moore's credibility. He isn't citing outside research here. He's citing himself.

Basically, Moore was caught recycling internet tropes and misdescribing his own cited sources rather than relying on the climate science.

Holman writes of the graph used in Chapter 3:

As for Ruddiman, he wrote in an email that his textbook, Earth’s Climate: Past and Future, isn’t the source of the graph’s data. “Someone else misquoted me as the source several years ago and Moore has repeated the error. I did not include that figure in my textbook because I did not trust the CO2/temperature data that far back.”

“If he’s saying that’s untrue, I’ll take it out,” responded Moore.

"No Hard Evidence" Is False on Its Face

Moore opens this chapter with a long list of climate predictions he says have "no hard evidence" behind them, calling all of it "conjecture based on the hypothesis" and computer models built by authors who supposedly decide what they want the model to predict. Set the list itself aside for a moment and look at the category error underneath it. A great deal of what he's dismissing isn't a model projection at all. It's a direct measurement.

Arctic sea ice extent has been tracked continuously by satellite since 1979 and shows a measured decline, not a projected one. Global sea level has been tracked by satellite altimetry, beginning with TOPEX/Poseidon in 1993 and continuing through today's Jason and Sentinel satellites, with NASA's own record showing the rate of rise has roughly doubled since the program began. Ocean acidification has been directly measured at Station ALOHA off Hawaii since 1988, tracking a steady, measurable drop in surface ocean pH as the ocean absorbs more atmospheric CO2. None of these are outputs of a climate model somebody tuned to get a scary answer. They're instrument readings — the exact kind of evidence Moore claims doesn't exist.

To understand CO2’s influence on climate change, it is essential to rely on credible sources and the overwhelming body of scientific evidence provided by climate scientists with the appropriate expertise and credentials — not a gold-investment blogger's chart, a mocked and misread NASA paper, or a report from the advocacy group Moore himself runs.

Read my rebuttal of the other Patrick Moore chapters here:

Exposing Patrick Moore
Patrick Moore Credibility
Chapter 1 Fact-check: Baobab Trees
Chapter 2 Fact-check: Coral Bleaching
Chapter 3 Fact-check: Carbon Dioxide
Chapter 4 Fact-check: Polar Bears
Chapter 5 Fact-check: Estimated Threats to Biodiversity
Chapter 6 Fact-check: The Great Pacific Garbage Patch
Chapter 7 Fact-check: Genetically Modified Foods
Chapter 8 Fact-check: Nuclear Radiation
Chapter 9 Fact-check: Wildfires Chapter 10 Fact-check: Ocean Acidification Chapter 11 Fact-check: Walruses