{"id":279180,"date":"2023-09-17T18:32:13","date_gmt":"2023-09-17T16:32:13","guid":{"rendered":"https:\/\/climatescience.press\/?p=279180"},"modified":"2023-09-17T18:32:34","modified_gmt":"2023-09-17T16:32:34","slug":"ipcc-guilty-of-prosecutors-fallacy","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=279180","title":{"rendered":"IPCC Guilty of \u201cProsecutor\u2019s Fallacy\u201d"},"content":{"rendered":"\n
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From Science Matters<\/a><\/p>\n\n\n\n

By\u00a0Ron Clutz<\/a><\/p>\n\n\n\n

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IPCC made an illogical argument in a previous report as explained in a new GWPF paper The Prosecutor\u2019s Fallacy and the IPCC Report.<\/strong><\/a>  Excerpts in italics with my bolds and added images.<\/p>\n\n\n\n

London, 13 September \u2013 A new paper from the Global Warming Policy Foundation reveals that the IPCC\u2019s 2013 report contained a remarkable logical fallacy.<\/strong><\/em><\/p>\n\n\n\n

The author, Professor Norman Fenton,<\/strong> 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<\/strong>. But as Professor Fenton explains, their logic in reaching this conclusion was fatally flawed.<\/strong><\/em><\/p>\n\n\n\n

\u201cGiven 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.<\/strong> They said there was less than a 5% chance that this was true.\u201d<\/strong><\/em><\/p>\n\n\n\n

\u201cBut they then turned this around and concluded that there was a 95% chance
that more than half of observed warming was man-made.\u201d<\/mark><\/strong><\/em><\/p>\n\n\n\n

This is an example of<\/strong> what is known as the Prosecutor\u2019s Fallacy,<\/strong> 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.<\/em><\/p>\n\n\n\n

As Professor Fenton explains<\/em><\/p>\n\n\n\n

\u201cIf 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\u2019s a classic error, and is precisely what the IPCC has done.\u201d<\/mark><\/strong><\/em><\/p>\n\n\n\n

Professor Fenton\u2019s paper is entitled The Prosecutor\u2019s Fallacy and the IPCC Report.<\/strong><\/a><\/em><\/p>\n\n\n\n

What the number does and does not mean<\/strong><\/em><\/h5>\n\n\n\n

Recall that the particular \u2018climate change number\u2019 that I was asked to explain was the number 95: specifically, relating to the assertion made in the IPCC 2013 Report of \u2018at least 95% degree of certainty that more than half the recent warming is man-made\u2019. <\/strong> The \u2018recent warming\u2019 related to the period 1950\u20132010. So, the assertion is about the probability of humans causing most of this warming.<\/em><\/p>\n\n\n\n

Before explaining the problem with this assertion, we need to make clear that (although superficially similar) it is very different to another more widely known assertion<\/strong> (still promoted by NASA) that <\/em>\u201897% of climate scientists agree that humans are causing global warming and climate change\u2019. That assertion was simply based on a flawed survey of authors of published papers and has been thoroughly debunked.<\/strong><\/em><\/p>\n\n\n\n

The 95% degree of certainty is a more serious claim.
But the\u00a0 case made for it in the IPCC report is also flawed.<\/mark><\/em><\/strong><\/p>\n\n\n\n

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