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Guest “They Googled ‘global temperature change since the last ice age’ and found a hockey stick” by David Middleton

Global Temperatures Over Last 24,000 Years Show Today’s Warming ‘Unprecedented’
A UArizona team created maps of global temperatures for each 200-year interval since the last ice age.

By Mikayla Mace Kelley, University Communications
Wednesday

A University of Arizona-led effort to reconstruct Earth’s climate since the last ice age, about 24,000 years ago, highlights the main drivers of climate change and how far out of bounds human activity has pushed the climate system.

The study, published Wednesday in Nature, has three main findings: 

It verifies that the main drivers of climate change since the last ice age are rising greenhouse gas concentrations and the retreat of the ice sheets.

It suggests a general warming trend over the last 10,000 years, settling a decade-long debate the paleoclimatology community about whether this period trended warmer or cooler.

The magnitude and rate warming over the last 150 years far surpasses the magnitude and rate of changes over the last 24,000 years.

“This reconstruction suggests that current temperatures are unprecedented in 24,000 years, and also suggests that the speed of human-caused global warming is faster than anything we’ve seen in that same time,” said Jessica Tierney, a UArizona geosciences associate professor and co-author of the study.

[…]

An online search of “global temperature change since the last ice age” returns a graph of global temperature change over time that was created eight years ago.

“Our team’s reconstruction improves on that curve by adding a spatial dimension,” Tierney said.

[…]

University of Arizona

This is what they Googled…

Figure 1. Source?

The paper is paywalled. The references listed after the abstract don’t seem to provide a source for the Googled temperature reconstruction.

My first thought was that this was from the fatally flawed Marcott et al., 2013 (M13). It’s the only 2013 global climate reconstruction listed in their references. However, M13 only goes back 11,300 years and isn’t nearly as Hockey Sticky as this graph.

They also listed Kaufman et al., 2020 (K20). However, it’s not from 8 years ago, only goes back 12,000 years and all five methods contradict the Googled graph, even the Hockey Stickiest methods.

I Googled “global temperature change since the last ice age” and the first return was the Eureka Alert (You Reek Alert) for their paper. I have only been able to find this particular graph in articles about their paper. Surely, someone in the WUWT community can identify the source of the image.

Mystery solved. See addendum.

Moving on…

The intrepid team of Googlers claim to have demonstrated the following:

  1. “It verifies that the main drivers of climate change since the last ice age are rising greenhouse gas concentrations and the retreat of the ice sheets.”
  2. “It suggests a general warming trend over the last 10,000 years, settling a decade-long debate the paleoclimatology community about whether this period trended warmer or cooler.”
  3. “The magnitude and rate warming over the last 150 years far surpasses the magnitude and rate of changes over the last 24,000 years.”

If the “retreat of the ice sheets” was a primary driver of the warming, what caused the ice sheets to retreat? Driver and amplifier are not synonyms.

K20, a paper they cited, pretty clearly contradicts all three of their findings, particularly the “composite plus scale” (CPS) reconstruction method.

It sure looks like almost all of the post glacial warming took place with a relatively minimal rise in atmospheric CO2.

Figure 2. “A funny thing happened on the way to the Anthropocene.” (WUWT)

All five methods indicate warming up until about 6,000 years ago and cooling over most of the past 6,000 years. The CPS method is the only one fully consistent with deglaciation and the subsequent neoglaciation; indicating very pronounced warming up until about 6,000 years ago (deglaciation) and cooling for most of the past 6,000 years (neoglaciation).

Figure 3. CPS with historical climate periods and Neoglaciation (Grosjean et al., 2007), Early Holocene ice extent map (Dyke et al., 2003) and Alps tree line altitude (Bohleber et al., 2021). (WUWT)

Setting aside the Hockey Sticks

Assuming the global reconstruction of instrumental temperature records and climate models are reasonably accurate (they aren’t, particularly the models), there is no need to invoke any anthropogenic forcing for any of the warming that occurred before about 1975.

Figure 4. Modeled human climate forcing compared to three instrumental records (see Terando for specifics). (WUWT)

Does anyone else here remember 1975?

If not for all of the warming allegedly caused by the combustion of fossil fuels, it would be colder now than it was when The Ice Age Cometh!

Figure 6. Modified after IPCC AR4. (WUWT)

This proud member of the Climate Wrecking Industry, say’s “You’re welcome!”

Addendum

An colleague just emailed me a copy of the paper. The mystery graph is from the 2021 paper. It is not the graph they referred to in this passage:

An online search of “global temperature change since the last ice age” returns a graph of global temperature change over time that was created eight years ago.

They must be referring to M13.

References

Bohleber, P., Schwikowski, M., Stocker-Waldhuber, M. et al. New glacier evidence for ice-free summits during the life of the Tyrolean Iceman. Sci Rep 10, 20513 (2020). https://doi.org/10.1038/s41598-020-77518-9

Dyke, A.S., Moore, A. and L. Robertson. [computer file]. Deglaciation of North America. Geological Survey of Canada Open File 1547. Ottawa: Natural Resources Canada, 2003.

Grosjean, Martin, Suter, Peter, Trachsel, Mathias & Wanner, Heinz. (2007). “Ice‐borne prehistoric finds in the Swiss Alps reflect Holocene glacier fluctuations”. Journal of Quaternary Science. 22. 203 – 207. 10.1002/jqs.1111.

Kaufman, D., McKay, N., Routson, C. et al. Holocene global mean surface temperature, a multi-method reconstruction approach. Sci Data 7, 201 (2020). https://doi.org/10.1038/s41597-020-0530-7

MacFarling Meure, C., D. Etheridge, C. Trudinger, P. Steele, R. Langenfelds, T. van Ommen, A. Smith, and J. Elkins. 2006. “The Law Dome CO2, CH4 and N2O Ice Core Records Extended to 2000 years BP”. Geophysical Research Letters, Vol. 33, No. 14, L14810 10.1029/2006GL026152. LINK Data

Monnin, E., et al.. 2004. EPICA Dome C Ice Core High Resolution Holocene and Transition CO2 Data.
IGBP PAGES/World Data Center for Paleoclimatology. Data Contribution Series # 2004-055.
NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

Osman, M.B., Tierney, J.E., Zhu, J. et al. Globally resolved surface temperatures since the Last Glacial Maximum. Nature 599, 239–244 (2021). https://doi.org/10.1038/s41586-021-03984-4

Terando, A., Reidmiller, D., Hostetler, S.W., Littell, J.S., Beard, T.D., Jr., Weiskopf, S.R., Belnap, J., and Plumlee, G.S., 2020, Using information from global climate models to inform policymaking—The role of the U.S. Geological Survey: U.S. Geological Survey Open-File Report 2020–1058, 25 p.,
https://doi.org/10.3133/ofr20201058.

via Watts Up With That?

2021 November 12