Two weeks before Dr. Michael E. Mann and colleagues published their 23 April 1998 “hockey stick” chart in Nature, a peer-reviewed journal published a paper asserting “an overwhelming majority of climate scientists” (50 out of 60) view catastrophic human-caused global warming – and even global warming itself – as an “unsupported assumption”.
At the time, satellite data indicated the lower troposphere had cooled by 0.13°C between 1979 and 1994. The Arctic had cooled by -0.88°C since the 1940s.
It was thought the IPCC had just (1995) perpetrated a “disturbing corruption of the peer-review process” in manipulating the conclusions of scientists to support favored government policies.
Image Source: Gardner, 1998
As of 1994 there was still so much uncertainty in the global temperature record that the 1995 IPCC report suggested the estimated warming since the mid-19th century was somewhere between 0.3 and 0.6°C, or about 0.45°C (IPCC TAR 2001).
Just 6 years later the IPCC emphasized a newly fangled certainty and precision in identifying global temperature trends. The “best estimate” was the Earth had warmed 0.61°C from 1861 to 2000.
Image Source: IPCC TAR 2001
In 2015 there were still scientists insisting there had been “no discernible warming since about 2000” (Dai et al., 2015).
Image Source: Dai et al., 2015
By 2019 – just four years later – it was claimed the globe had warmed 1.2°C since the 19th century and the IPCC warned the Earth has 12 years left (2030) to avert a “climate catastrophe” (Gunningham, 2019).