by P. Homewood, Aug 16, 2021 in NotaLotofPeopleKnowThat
That there has been 1.1°C of warming since 1850 is not especially controversial. There is some disagreement about the degree to which it reflects the “recovery” from the mini-Ice Age (when there were Ice Fairs on the Thames among other events not seen today) and the effects of increased CO2 emissions.
The controversial part is the removal of temperature oscillations commonly thought to have occurred over the course of the past 2,000 years. These include warming that was known to have occurred in Roman times and again in the tenth century when the Vikings colonised Greenland until 1250, and the cold period 1400-1700. Such events are downgraded as being either exaggerated or localised.
The earlier iteration of the IPCC 2021 picture was the notorious hockey stick fabrication by Michael Mann. Mann cherry-picked data from tree rings and spliced together incongruent data sources, and reported his “findings” in a 1998 paper. Like the latest IPCC report, this showed a flat temperature trend until the 20th Century, then a sharp rise.
The IPCC in its 2001 report used Mann’s graph as its poster child to substantiate human-induced global warming. In the years after 2001 the IPCC quietly dropped Mann’s “hockey stick”. Its discreditating was completed by 2009 release of confidential emails (dubbed “Climategate”), which showed Michael Mann as the conductor of other climate scientists seeing a need to eradicate the “medieval warming period” in order to make the case that the modern warming is unique.
The chicanery under which this strategy was conducted resulted in legal cases. Canadian scientist Tim Ball called Mann a fraud, Mann sued and the subsequent court case lasted a decade before finding against Mann. (Mann has managed to string out another case that he brought against Mark Steyn for even longer).
But in the 2021 climate review the “hockey stick” is again the main feature.