Video of Dr David Deming's statement to the U.S. Senate Committee on Environment & Public Works on December 6, 2006. Dr Deming reveals that in 1995 a leading scientist emailed him saying "We have to get rid of the Medieval Warm Period". A few years later, Michael Mann and the IPCC did just that by publishing the now thoroughly discredited hockey stick graph.
https://www.youtube.com/watch?v=u1rj00BoItw