The epilogue. We have been discussing the hockeystick here over the years now, a few threads: https://www.physicsforums.com/showthread.php?t=49049 https://www.physicsforums.com/showthread.php?t=61419 https://www.physicsforums.com/showthread.php?t=75609 https://www.physicsforums.com/showthread.php?t=94621 The wrap up of the story very shortly, In the 1990ies the IPCC wanted to determine the forcing function of greenhouse gasses. But this is hard as the signal is contaminated with natural climate variation. So one of the areas of research was the last millennium, which appeared to be characterized by an early Medieval Warm Period to be followed by a Little Ice Age. Both were obviously not related to greenhouse gas variation and would blur the investigation about empiric greenhouse forcing significantly However as soon as the IPCC started to work, both those periods started to become doubtful and in the fall meeting of the American Geologic Union in 1998, Overpeck had got rid of the Medieval Warm Period. (Surprisingly it’s no longer on the net, but googling you may find some references to it). To prove that those periods have not existed, Mann Bradley and Hughes (MBH) carried out ‘multiproxy’ studies, reconstruction the climate of the past. The graph of the global temperature of the last millennium, the hockeystick promoted to Fig 1B of the http://www.ipcc.ch/pub/spm22-01.pdf [Broken], page 3 which correlated incredibly accurate with the CO2 hockeystick (fig 2a) on page 6. So, apparently no more doubt, and from the spikes in the last century it seemed obvious that greenhouse gasses have a very dominant role in global temperatures and that natural variability had been very small in the last millennium. But somehow some people were not convinced of such a construction and these people became known as skeptics. Curiously enough skepticism is an intrinsic part of science, and the core of the scientific method but somehow in climate science it became equivalent to immoral greedy hoodlums. But anyway, Several attacks were made on the poster child graph, the most persistent being from Steve McIntyre and Ross McKitrick (M&M), who audited the methods, showing that a lot was wrong. More details here. Incidentally, the geologic fieldwork continued and evidence of a worldwide Medieval Warm Period accumulated as can be seen http://www.co2science.org/scripts/CO2ScienceB2C/data/mwp/mwpp.jsp [Broken]. The same is true for the Little Ice Age. So,two committees looked at the work. The NAS committee agreed with the critique of M&M but confirmed also the dire climate changes brought about by anthropogenic greenhouse gasses. Then the Wegman report for the Barton hearing also confirmed the “errors” in the MBH methodology, as Mann could not defend these “errors” adequately yesterday the hockeystick can be considered death. I wonder how long the burial will take. It may also be clear that normally the damage for climate science would be considerable, the Third Assessment Report and it Executive Summary hinged completely on the hockeystick and so do numerous other publications. So the natural variation is indeed much larger than the hockeystick intended to suppress. A genuine mistake or a hoax? It may also be clear that further reference to the Hockeystick as official information regarding climate issues could be subject to nationals laws pertaining integrity and honesty for disclosure of information.