A new paper from the Global Warming Policy Foundation reveals that the IPCC’s 2013 report contained a remarkable logical fallacy.
The author, Professor Norman Fenton, shows that the authors of the Summary for Policymakers claimed, with 95% certainty, that more than half of the warming observed since 1950 had been caused by man. [emphasis, links added]
But as Professor Fenton explains, their logic in reaching this conclusion was fatally flawed.
“Given the observed temperature increase, and the output from their computer simulations of the climate system, the IPCC rejected the idea that less than half the warming was man-made. They said there was less than a 5% chance that this was true.”
“But they then turned this around and concluded that there was a 95% chance that more than half of observed warming was man-made.”
This is an example of what is known as the Prosecutor’s Fallacy, in which the probability of a hypothesis given certain evidence is mistakenly taken to be the same as the probability of the evidence given the hypothesis.
As Professor Fenton explains:
“If an animal is a cat, there is a very high probability that it has four legs. However, if an animal has four legs, we cannot conclude that it is a cat. It’s a classic error, and is precisely what the IPCC has done.”
Professor Fenton’s paper is entitled The Prosecutor’s Fallacy and the IPCC Report.
Norman Fenton is Professor Emeritus of Risk at Queen Mary University of London (retired as Full Professor, December 2022) and a Director of Agena, a company that specializes in artificial intelligence and Bayesian probabilistic reasoning. He is a mathematician by training, with a current focus on quantifying risk and uncertainty using causal, probabilistic models that combine data and knowledge (Bayesian networks). He has published seven books and over 350 peer-reviewed articles. His work covers multiple domains, including law and forensics, health, and system safety. Since 2020 he has been active in analysing data related to Covid risk.
Sorry, but this is NOT a logical fallacy. You have an exclusive binary question, is the anthropogenic share above, or below 50%. It is either this, or that. We can substitute and say it is either a or b. If it is a it will not be b, and if it is b, it will not be a. If a has a chance of 5%, b will necessarilly have a chance of 95%. It is all fine.
Now it [doesn’t] mean the models have it right, but that is a different story. Also there are massive fallacies in the science, but this ain’t one of which.
E.,could you please tell us what you meant to say in that last paragraph?
Sonnyhill, I am thinking that the third word in the paragraph was supposed to be doesn’t. Then the paragraph makes sense.
Correct, sorry
The fallacy is the false claim that ANY HUMAN KNOWS THE PERCENTAGE OF CLIMATE CHANGE THAT IS NATURAL vs. MANMADE.
Agreed, but I can control the temperature in my house. That’s man made, and that ability and our choices are threatened by climate alarmist charlatans that want to rule the world. Weed them out.
The IPCC Summary for Policy Makers quite often omits good research. Censorship? Smells like it. The Summary stokes climate alarmism, makes Al Gore a very rich man. We’re going to boil the oceans? Propaganda.
The UN set up the IPCC in 1988 specifically to deliver meta-analyses of papers on man-made climate change. They therefore ignore the many findings to the contrary.