In this
light paleo research is very important too — as
indeed when one looks at high - CO2
warm periods (for instance in the Tertiary) some data seems to suggest a climate sensitivity that would be somewhat higher than the IPCC range.
Earlier this year, a paper by Michael Mann - for years a leading
light in the IPCC, and the author of the infamous «hockey stick graph» showing flat temperatures for 2,000 years until the recent dizzying increase - made an extraordinary admission: that, as his critics had always claimed, there had
indeed been a» medieval
warm period» around 1000 AD, when the world may well have been hotter than it is now.