Often we hear that 97% of climate scientists agree that anthropogenic climate change is occurring. This is repeated time and again to demonstrate the foolishness of 'deniers' ... how can they deny science? So where did this statistic come from? Well this isn't the origin of it... but it certainly is a popular statistic. First off there are two levels here... 1. The climate is changing. 2. The climate is changing because of mankind's influence. So where'd this come from? Well it started in 2004 with Naomi Oreskes published this short article https://science.sciencemag.org/content/306/5702/1686.full.pdf+html In this she clearly identified 100% of papers she studied to be endorsing the consensus view on Climate Change [that it is man made] Image 1: [from the above link] Oreskes later went on to write a book [ https://www.lpl.arizona.edu/sites/default/files/resources/globalwarming/oreskes-chapter-4.pdf ] where she discussed this further... offering this: Clearly scientifically there was a consensus... 100% of papers studied do indeed show no refutation of the idea of "global climate change". But the leap from "global climate change" to "man-made global climate change" is unsupported. Indeed in the very next line after image 1 Oreskes says that some study authors "might believe that current climate change is natural". While not damning, this caveat has been subsequently ignored in reporting. But in 2013 John Cook and others [see image below] published a report which was the strongest evidence yet to support the 97% claim. https://iopscience.iop.org/article/...E518E7763C764921E71.c1.iopscience.cld.iop.org This looked at nearly 12,000 report abstracts. Not the reports themselves. But the easily digested cover sheet. And what did they find? And there is the origin of the 97% claim. Out of 11,944 papers they found that 3,894 supported AGW. And this has spun out into meaning 97% of scientists. Not "97% of scientists who expressed an opinion"... just 97% of scientists. This paper has, of course, been a source of controversy. It was rebutted here: https://link.springer.com/article/10.1007/s11191-013-9647-9 Unfortunately only the abstract is available [ironically considering] This paper of course elicited a rejoinder from Cook: https://research-repository.uwa.edu...c-consensus-and-the-teaching-and-learning-of- defending their conclusions [as they are perfectly entitled to do]. Had to go looking for that one because it isn't on Cook's website. Not sure why. Cook also went on to publish: https://iopscience.iop.org/article/10.1088/1748-9326/11/4/048002/pdf Which has this handy little chart Always love a handy chart. Cook even produced this nice chart: After analysing surveys of peer reviewed articles. Cook was careful to say it was based on 'climate experts' but that didn't stop the media and politicians like Obama and John Kerry running with "97% of scientists" ... a statement that is just simply untrue. Unfortunately, Cook was not supported by many of the scientists who he'd surveyed. Even within those who do believe [accept] that humanity is playing a role in climate change [and I'm in that camp myself] there is a range of views. Source: http://www.hvonstorch.de/klima/pdf/CliSci2013.pdf 1 is not convinced and 7 is very convinced. So here we can see that 70% of scientists hold a very strong/strong belief in AGW. Whatever way that you look at it, the majority of climate scientists who've expressed an opinion do think that humanity is having a strong effect on the climate. But the next time you see "97%" quoted at you... just bear in mind how deeply inaccurate that is... and how nuanced the actual discussion is.