Roberts tries the Galilieo Gambit

In the often dry halls of Senate Estimates, we recently witnessed a masterclass in what can only be described as confident ignorance. Senator Malcolm Roberts, a man who has made a career out of "questioning" the atmospheric physics that the rest of the world accepts as reality, squared off against Dr. Karl Kruszelnicki.

When Dr Karl raised consensus among scientists as a point against Roberts’ arrogance. Roberts scoffed, pursuing an argument which, on the surface, seems profoundly intellectual: Science is based on evidence, not consensus. It is a line designed to frame the Senator as a modern-day Galileo, standing alone against a dogmatic priesthood of "alarmist" scientists.

But as Dr. Karl’s visible frustration suggested, this argument isn't just wrong - it’s a fundamental betrayal of how science actually functions. When Roberts invokes the "consensus vs. evidence" trope, he is leaning on the Galileo Gambit. The logic goes like this: The establishment once laughed at Galileo; the establishment now disagrees with me; therefore, I am Galileo.

The flaw in the argument is so large you could drive a proverbial coal train through it. Galileo wasn't right because he was a rebel; he was right because he had better data. He pointed a telescope at Jupiter and saw moons that shouldn't be there according to the prevailing model. He replaced a consensus of faith with a consensus of observation.

And Galileo ‘moments’ are extremely rare in science. When an engineer sees a crack in a bridge, they are drawing on a wealth of experience and observations accumulated over centuries. The consensus that the bridge is dangerous is not derived from some kind of popularity contest. The consensus comes from each engineer seeing the same thing and reaching the same conclusion because all other conclusions are stupid.

In contrast, modern climate sceptics aren't offering a new, more accurate model of the universe. They are cherry-picking the "cracks" in the concrete of a bridge that 99% of engineers are telling them is about to collapse.

The most exhausting part of this exchange - and the source of Dr. Karl’s palpable exasperation - is the suggestion that consensus and evidence are opposing forces.

In science, consensus is the result of evidence, not a substitute for it. Scientists are inherently competitive; you don't win a Nobel Prize by agreeing with everyone else. You win it by proving everyone else wrong. The reason we have a "consensus" on human-induced climate change is that for forty years, thousands of scientists have tried to disprove it and failed.

When Dr. Karl attempts to explain the basic physics of the greenhouse effect, he isn't citing an "opinion poll." He is citing the accumulated, peer-reviewed, and verified data of the global scientific community.
The vulnerability in the "consensus" argument is that it sounds like groupthink to the uninitiated. To someone like Roberts, the 97% figure feels like a conspiracy. But to a scientist, that 97% represents a mountain of data so high that you can no longer see the ground.

By framing the debate as "Evidence vs. Consensus," Roberts isn't engaging in science; he’s engaging in marketing. He uses the language of scepticism to shield himself from the results of actual sceptical inquiry.

Watching Dr. Karl navigate this exchange was a reminder of the "asymmetry of nonsense." It takes ten times more energy to debunk a fallacy than it does to invent one. When one side is armed with the laws of thermodynamics and the other is armed with a misunderstood history of 17th-century astronomy, "debate" becomes a farce.

We must stop pretending that "questioning the consensus" is a virtue when you are simultaneously ignoring the evidence that built it.