Interviewee makes false claims about warming, CO2, climate models
A British television interview viewed tens of thousands of times on social media features a man claiming that global warming is natural, CO2 has no provable effect on the climate, the greenhouse effect is negligible, and computer models used to measure climate change are skewed. But the speaker is not a climate specialist, experts say the claims are false, and world scientists overwhelmingly agree that humans are heating the planet by burning fossil fuels.
The interview with Brian Catt, introduced as a "physicist and electrical engineer and an MBA", was broadcast on the channel TalkTV and posted on its Facebook page on August 14, 2022. It was widely shared on Facebook and Twitter.
Asked whether people are "right to panic" about climate change, Catt replied: "They should relax basically, simply because if they were to go and look at the natural history of the Earth, which has all been unravelled since these climate myths were created by the UN, they'd find that actually what is happening now is almost totally normal."
In the eight-minute excerpt of the interview, Catt makes several further unfounded claims about global climate change. Climate specialists interviewed by AFP explained why the claims are false. Their responses are detailed below.
Catt's LinkedIn profile says he took a degree in physics in 1971 and later studied business. An article published on August 24 on the investigative climate website DeSmog detailed some of Catt's activities, including a blog post he published accusing the United Nations and green campaigners of using "Nazi" methods to impose a "Marxist dystopia".
"He doesn't have any qualifications or a scientific publication record in this area and he's essentially rejecting the expert conclusion of every credible scientific organisation around the world," said Bob Ward, policy and communications director at the Grantham Research Institute on Climate Change and the Environment at the London School of Economics.
Current climate change not part of normal cycles
Catt said global temperatures have risen and fallen over millennia and the heating of the planet in recent decades is not due to human causes, stating at one point that "CO2 has no provable effect on the climate."
"For the last 10,000 years, which is a short warm period within an ice-age cycle, it goes up and down about a degree at the equator, two degrees at the poles, about every thousand years and it's perfectly normal and the rates of rise now ... is not unusual either," he said.
Ward and Ed Hawkins, a professor of climate science at the University of Reading, said that temperature fluctuations comparable to the current warming have not happened on that timescale during the past 10,000 years.
"Global temperatures have oscillated over a large range in the past but those changes take tens of thousands of years to happen. We understand there are natural causes for those cycles, due to Earth's orbit around the sun. Climate scientists have studied this for centuries," Hawkins said.
"What we see over the last 2,000 years is a very gentle decline, then suddenly at the end you see a rapid uptick in temperature, way above anything we've seen in the last 2,000 years," he added.
"The claim that that is normal is simply not true -- it is very abnormal when we look back over the global records, way outside anything we've seen over the past 2,000 years in terms of the rapidity and the spatial coherence," of the rise.
The left-hand chart shows temperatures rising sharply in the past 150 years. On the right-hand chart, the blue line at the bottom shows how much lower global temperatures would be without the impact of humans releasing CO2 and other greenhouse gases by burning fossil fuels:
The claim that recent warming is normal because temperatures have been seen to rise and fall over millennia "is just stupid logic," said Mike Lockwood, professor of space environment physics, also at the University of Reading.
"It is of course true that temperatures have risen and fallen in the past but that is not a reason for assuming that the present change has the same causes as past ones."
The IPCC reviews studies to summarise the state of knowledge about how humans are driving climate change, using reports compiled by hundreds of scientists in dozens of countries. In the first part of its latest major report in 2021 it said: "It is unequivocal that human influence has warmed the atmosphere, ocean and land."
Sun doesn't cause global warming
Scientists agree that carbon emissions from humans burning fossil fuels have increased the greenhouse effect, driving up the level of carbon dioxide in the atmosphere that traps heat near the Earth's surface.
Catt downplayed the greenhouse effect and said other factors were causing global warming. "It's a very small effect, the greenhouse effect, within the overall parameters of the atmosphere. There are much bigger things at work like the sun shining on it and the gravity pulling the atmosphere onto the ground ... the clouds are the control of Earth's climate stability," he said.
Scientists responded by citing well-documented findings that show the Sun's variations have not been strong enough to change the Earth's climate.
Lockwood said solar activity rose in the 1950s-1960s and fell back again in 2008-2019 even as the rise in global temperatures accelerated. "This shows how very minor all solar effects are compared to the real causes of global temperature rise," he said.
He provided the following charts, drawn from the UK Met Office's HadCRUT climate data series. The top two curves show global temperatures (top) and CO2 concentration (second from top) rising since the 1960s, while the number of sunspots -- indicators of solar energy (third chart) -- and total solar irradiance (bottom chart) have declined overall:
Hawkins said: "We have good records of direct measurements of the amount of energy from the Sun from satellites and sun-spot numbers going back a very long way, so we understand variations in the Sun's output. The Sun has a roughly 11-year cycle. We don't see a big 11-year change in climate, so that can't be having a big impact."
He said what is known is "that the Sun's got slightly less bright over the past 50 years, which is when we've seen the most rapid warming."
The US space agency NASA sums up the impact of solar irradiance on the Earth's climate here. "The Sun's energy output only changes by up to 0.15% over the course of the cycle, less than what would be needed to force the change in climate that we see," it says.
"If the Sun were driving Earth's warming, one would expect to see that upper atmosphere getting increasingly hot," it adds. "Instead, measurements show the lower atmosphere is getting hotter, while the upper atmosphere is getting cooler."
The conclusion is echoed in a summary by the World Meteorological Association. "The rise in temperatures -- which are melting ice and heating the oceans -- is driven by long-lived greenhouse gases in the atmosphere," it says.
The confirmation that warming at Earth's surface is due to increased levels of CO2 came from a model developed by Japanese-US climatologist Syukuro Manabe. He won the Nobel Physics Prize in 2021 for the model:
Regarding the comment on gravity, scientists consulted by AFP said it was not clear what Catt meant.
"Does he mean Milankovich orbital cycles?" Lockwood said, referring to variations in the Earth's orbital movements. "Their effect is well known and understood. Changes are very slow compared to recent climate change."
Ward also said he was unsure about the gravity comment. "If gravity is pulling the atmosphere closer then we should be able to measure that and it would already be having an effect on us as people," he said.
As for clouds, the scientists said they do not drive climate change.
"Clouds are part of the climate system and not an external influence," said Lockwood.
Hawkins said that current models account for small changes to the properties of clouds. "They have an impact but it's factored in."
Climate models take natural variables into account
At the end of the clip Catt criticised the computer models used by climatologists to measure and forecast the impact of human-driven global warming. (Some users shared a shorter excerpt from the interview which did not include these claims.)
"The initial statement is CO2 causes the problem, when in fact it probably doesn't. So what they do is, they quietly skip around that, ignore the fact that climate changes naturally, feed into their models a causal relationship between carbon dioxide," he said.
The scientists interviewed denied that the models are skewed in this way. Hawkins said the natural factors mentioned have long been known about and factored in to calculations.
"The models are millions of lines of code in some cases. We encode in a computer all of our understanding of the physics, chemistry and biology of the atmosphere, the oceans and the land. This is the same basis as that of weather forecast models, which most people recognise represent the atmosphere very accurately," he said.
"But the fact that CO2 absorbs infrared radiation is something you can measure in a school laboratory. If you change the level of greenhouse gases in the atmosphere, the planet's temperature will change."
Lockwood said the whole point of models was to control for variables such as the natural factors mentioned.
"Detection-attribution techniques use climate models to identify the relative contributions of anthropogenic and natural causes," he said. "They can only do this specifically because the models predict and allow for both anthropogenic and natural effects. The idea that the latter are ignored is laughable."
Catt claimed that many of the studies citing forecasts based on climate models were "not reproducible" for purposes of scientific scrutiny.
"People make up these things, feed them into models and say we proved them because the model says so," he said. "The climate models on average are producing... 250 percent error in the amount of warming they predict."
He did not cite a source for the figure.
Ward of the Grantham Research Institute said the models have a long history and are repeatedly reviewed by scientists.
"The models are tested by their ability to reproduce recent trends in climate and those that are successful are the ones that end up being used to make projections of the future," he said.
"You wouldn't trust a car or a bridge or a building that had been designed without the use of a computer model. If any engineer tried to build anything nowadays without using a model, he'd be laughed out of town."
Regarding Catt's claim, he added: "The only way he can get away with it is if he claims there's a global conspiracy between hundreds of thousands of scientists who all know that these models are flawed but are refusing to say anything about it -- and that is just silly."
The Met Office published a description of its HadGEM3 climate model in a research article here.
Ward judged that coverage on TalkTV was "politically driven", addressing an audience of "hardcore climate sceptics who think that net-zero [climate targets policy] is to blame for the energy crisis".
He identified Catt as a regular commentator in climate-denial circles and media. Investigative site Desmog reported that Catt had been quoted by the British climate science denial group CAR26, which the site says has links to the right-wing Reclaim Party.
Tice also referred in passing to recent claims of "good news that the Great Barrier Reef" has "record levels of coral cover". AFP addressed related misleading claims on that subject in another recent fact check.
More of AFP's fact-checks on climate related claims are available here.
August 24, 2022 Updated to add link to article about speaker, add quotes in penultimate section and remove quote in last section.