An Australian senator has attempted to undermine the entire theory of the greenhouse effect with a bizarre viral claim that scientists have been ignoring gravity’s role in heating the planet.
The tweet from the Queensland senator Gerard Rennick, a member of the conservative Liberal National party of Queensland which is part of the main opposition Coalition, has gone viral this week and has been met with scorn, derision and plenty of corrections from high-profile climate scientists.
“Senator, you should be thankful you can’t be impeached for ignorance,” wrote Prof Michael Mann, a leading climate scientist at the University of Pennsylvania.
In the tweet, made last month and viewed more than 850,000 times, Rennick posted a video with the words “scientists ignore the fact that gravity plays a role in heating the earth … That’s why ‘Net Zero’ CO2 emissions won’t stop ‘Climate Change’.”
The video features Rennick appearing in a session of parliament where he asked a bemused head of a government science agency whether “gases [in the atmosphere] trap convection”.
CO2 is a gas, it cannot trap convection. This matters because convection is the process by which heat is carried away from the earth.
— Senator Gerard Rennick (@SenatorRennick) March 16, 2023
What traps convection is gravity. It’s why the surface of the earth is warmer than say the top of Mt Everest...
More 👇https://t.co/pad5svjAhT pic.twitter.com/HpEAGiGVK1
Dr Chris Colose, a climate scientist at Nasa, replied on Twitter that Rennick’s question “do gases trap convection”, “doesn’t even make sense as a statement. Nor does it discount the importance of [greenhouse gases].”
In an article linked from the tweet, Rennick, whose biography says he has degrees in taxation, commerce and finance, wrote that gravity was “overlooked by climate scientists who want to blame CO2 for trapping heat in the atmosphere”.
All of this, according to Rennick, meant CO2 was not responsible for global heating. Climate change was “junk science”, he wrote.
Engaging on Twitter, Mann described Rennick’s statement as “gibberish” and a “stringing together of scientific terms reminiscent of monkeys typing on a typewriter”.
When Rennick accused Mann of “cancelling gravity” in his explanations of the greenhouse effect, Mann showed him a mathematical explanation of how air temperatures change depending on altitude.
p.s. "canceling gravity"? Given your extensive background in atmospheric physics, surely you're aware of what "g" stands for in this derivation? 😆https://t.co/vsPEMxko13
— Prof Michael E. Mann (@MichaelEMann) April 2, 2023
Associate Prof Sarah Perkins-Kirkpatrick, a climate scientist at the University of New South Wales Canberra, pointed to Rennick’s areas of expertise, which don’t include atmospheric physics or climate science.
“He’s got no expertise whatsoever. It’s a bit like me going and doing someone else’s taxes. I wouldn’t. There’s no point,” she said.
Rennick wrote that adding CO2 “doesn’t add to the overall heat in the system” but Perkins-Kirkpatrick said it does trap more heat – a property of CO2 established in the 19th century.
Rennick tried to argue the “first law of Thermodynamics” meant “energy can neither be created or destroyed, only transferred or transformed”.
He wrote any radiation absorbed or emitted by CO2 “doesn’t add to the overall heat in the system”.
But Perkins-Kirkpatrick said Rennick had again misunderstood the basics because energy entered the Earth’s atmosphere from the sun, and energy also left the atmosphere.
“Yes, energy can’t be created or destroyed but it does leave the Earth’s system. The Earth isn’t closed off. It’s part of the universe,” she said.
Scientists measure the Earth’s energy imbalance – that is, the difference between how much energy from the sun is absorbed by the Earth and how much radiation is emitted back out to space.
A 2021 study found this imbalance – caused mostly by adding greenhouse gases to the atmosphere – had doubled between 2005 and 2019, causing the Earth to gain more heat.
Rennick, who once accused the country’s weather bureau of engaging in a conspiracy to alter climate records, said it was “categorically false” that CO2 trapped heat like a greenhouse, because a greenhouse or blanket “traps convection because it a solid object”.
The common analogy that greenhouse gases act like a blanket around the planet is not supposed to describe exactly how the atmosphere works.
Perkins-Kirkpatrick said the analogy “isn’t perfect” but it gave a good example of how adding extra greenhouse gases to the atmosphere trapped more heat near the Earth’s surface.
Prof Steven Sherwood of the Climate Change Research Centre at the University of NSW, said: “There’s a saying in science when you really want to cut something down. ‘It’s not even wrong.’”
He said the role of convection was well understood. “It’s important and it is part of global warming. It is how heat gets to upper parts of the atmosphere. But we know that. It doesn’t falsify global warming. There’s just no logic [to Rennick’s tweet].”
Dr Andrew King, a climate scientist at the University of Melbourne, said both gravity and convection were included in climate modelling, and to suggest they were ignored was “complete nonsense”.
“It’s quite concerning that this is coming from an elected official. I think often as scientists we think people are sick of hearing about climate change and have quite a good grasp of the greenhouse effect. But maybe not. There’s still a big knowledge gap there in the office of Senator Rennick.”
