The IPCC’s latest report uses a hockey stick-shaped reconstruction of global temperatures that wholly contradicts previous records  produced by the same PAGES 2k and Oceans 2k consortiums from 4 years earlier.

In 2015, the PAGES 2k Consortium published an updated (“corrected”) 0-2000 AD global reconstruction that showed a large portion of the 1st millennium was globally as warm or warmer than the last 30 years of the 20th century.

The authors added a red-hot near-vertical line to to the 30-year bins to emphasize modern warmth even as they acknowledged the late 300s CE, as well as the 1941-1970 period, were warmer (Arctic) than 1971-2000.

As the pink-blue graph on the bottom of the image below shows (coloration/annotation added, red line removed), the anomalous temperatures (blue) in the last 2000 years occurred during the globally-coherent Little Ice Age. Late 20th century warmth was only a partial return to the 1st millennium climate “normal” (pink).

Image Source: PAGES 2k Consortium

Just 4 years later (2019), PAGES 2k scientists apparently decided an as-warm or warmer 1st millennium did not sufficiently advance the anthropogenic global warming narrative. So they flattened the 1st millennium warmth so it was effectively indistinguishable from the Little Ice Age.

Image Source: PAGES 2k Consortium (pdf)

After making 1st millennium warmth and Little Ice Age cooling disappear, the PAGES 2k agenda was then to create a hockey stick blade clearly distinguishable from the rest of the record. This served to make modern warmth appear unprecedented.

Image Source: PAGES 2k Consortium (pdf)

The newly-created hockey stick blade not only contradicted PAGES 2k (2015), it also was wholly incongruent with Oceans 2k (2015), the PAGES 2k Consortium global sea surface temperatures reconstruction (representing 71% of the Earth’s surface).

Notice the Oceans 2k authors indicate there was a warming trend of just 0.08 of a standard deviation unit per 100 years during the 1801-2000 AD period, whereas there was a temperature variation (cooling) of more than twice this rate (-0.17 and -0.18 s.d. unit/100 years) during the “globally coherent” Little Ice Age bins (1201-1400 and 1601-1800 AD). Also notice the 1st millennium was nearly a full 1 standard deviation unit warmer than 1801-2000.

Image Source: McGregor et al., 2015 and supplemental data 

Here’s how the 20th century warming would likely appear had the authors been willing to display it at the end of the record.

This manifestation undermines any claims of an unprecedented, hockey-stick-shaped warming in the modern era.

Image Source: McGregor et al., 2015 and supplemental data 

Other global ocean (Gebbie and Huybers, 2019) and land (Northern Hemisphere, Büntgen et al., 2020) reconstructions also contradict PAGES 2k (2019), as they show both a globally coherent Medieval Warm Period and Little Ice Age.

Of course, these temperature records must be excluded and/or ignored in IPCC AR6.

Image Source: Gebbie and Huybers, 2019

Image Source: Gebbie and Huybers, 2019 and supplemental data

Image Source: Büntgen et al., 2020

via NoTricksZone

August 16, 2021