Was the Medieval Heat Interval “regional”? – Watts up with that?

Reposted by MANHATTAN CONTRARIAN

January 03, 2021 / Francis Menton

Some commentators noted yesterday that the climate establishment has not entirely ignored the threat to its orthodoxy from the Medieval Warm Period and other similarly warm epochs prior to human emissions. It was initially recognized that this issue might be important and there was definitely an attempt to address it. However, as time went on, the accumulation of evidence, particularly for the existence of the Medieval Warm Period as a global phenomenon, has gradually become overwhelming.

So – given the evidence that under the normal prescriptions of the scientific method, the hypothesis that only human CO2 emissions could cause current warming becomes invalid – how can Orthodoxy be kept alive? The answer was almost entirely to resort to the waving of the hand of “recognition and attribution studies” and hope that no one would notice. And nobody notices it to a remarkable extent.

Readers may be interested in a brief history of this issue.

• The first IPCC assessment reports, published in the 1990s, included climate history charts showing that the Medieval Warm Period was warmer than the current period despite human CO2 emissions in the current period. In the late 1990s, the clique of climate researchers, primarily responsible for drawing up the next IPCC report, due in 2001, recognized this as a problem.
• In about 1996 a scientist named David Deming received an email from a member of the insider clique named Jonathan Overpeck. Deming later described the email as a testimony before the Senate Committee on Environment and Public Works. Deming’s statement is quoted as follows in a 2013 post in Watts Up With That: “With the publication of the article in Science [in 1995]I have gained considerable credibility in the community of scientists working on climate change. They thought I was one of them, someone who was going to pervert science in the service of social and political causes. So one of them let go of his guard. An important person in the field of climate change and global warming sent me an amazing email titled “We Must Get Rid of the Medieval Warm Period.” According to the WUWT post, Deming did not specifically identify Overpeck in his testimony, but it did circulate “Rumors” that the email was from Overpeck. Overpeck then declined to send such an email. However, after Overpeck made the rejection, another email emerged from Overpeck to Keith Briffa (another member of the Inside Climate clique) in 2005 in which Overpeck said, “I’m not the only one dealing with one wants to deal with fatal blow against the misuse of alleged terms and myths from the warm period in literature. “
• In 1998 and 1999, Michael Mann and co-authors published two articles in Nature describing temperature reconstructions from the year 1000 and beyond. Included in these articles was a diagram of a temperature reconstruction for the northern hemisphere dating back to 1000. The graph showed that temperatures remained essentially flat from around 1000 to around 1940, after which the steepest increase has occurred in recent years. In other words, the medieval warm period was gone. This graphic quickly became known as the “hockey stick” due to its iconic shape.
• In 2001 the IPCC published its third assessment report on the world climate. The hockey stick diagram had taken over the narrative in full and appeared as a guiding diagram in the executive summary and several other places in the report. The abolition of the MWP was never mentioned as such, but astute observers could easily see how the graph solved the problem of the gaping logical flaw in any argument that recent warming could have been caused only by human CO2 emissions. A version of the hockey stick diagram published in the 2001 Third Assessment Report is shown at the bottom of this post.
• Over the next five years, the basis for Mann’s hockey stick graphics was gradually and thoroughly destroyed. A longer version of the story appears in a post I wrote here in 2019. Decryption began around 2003 with a very talented Canadian mathematician named Stephen McIntyre trying to replicate Mann’s work and making a request for Mann’s complete data and methods. McIntyre was met with resentment and hostility. McIntyre then embarked on the very arduous process of replicating Mann’s work without access to the data and methods, and eventually found that Mann had used flawed statistical methods and selected data to get the reconstruction he wanted.
• After the hockey stick was demolished, an alternate narrative was needed to support the position that the Medieval Warm Period did not exist. By 2009, the main creator of Hockey Stick, Mann, had turned to the new narrative, namely that the evidence for the MWP had only come from certain limited “regions” and therefore it could not be said that the era was a global warm period like the current era was. Here is a 2009 Penn State News article (taught in Penn State Mann) that quoted Mann as saying, “These terms can be misleading,” Mann said. “Although the Middle Ages appear a little warmer around the world compared to the later centuries of the Little Ice Age, some key regions were actually colder. For this reason, we prefer to use the “medieval climate anomaly” to underline that while there were significant climate anomalies at the time, these differed greatly from region to region. “
• Nice try. Efforts to reduce MWP to just “regional” have inspired several organizations and individuals to compile lists of research that cover all areas of the world and reconstruct temperatures from the approximate MWP years 1000-1250. One of the most comprehensive collections I am aware of was compiled by Craig Idso of the Center for the Study of Carbon Dioxide and Global Change. Idso has listed well over 100 studies from literally all parts of the world, broken down into categories such as Africa, Antarctica, Asia, Australia / New Zealand, Europe, North America, Northern Hemisphere, Oceans, and South America. As with the hockey stick graphic, the idea that the MWP was merely “regional” was thoroughly destroyed.

The dozen of studies compiled by Idso and others have placed proponents of the “human causation” hypothesis in a near-impossible position. One or two or five studies can be flawed and / or easily refutable. But more than a hundred? And from all over the world?

And so the proponents of the “human causation” hypothesis have again changed the subject. Instead of following the scientific method of falsifying the hypothesis, we are now talking about the hocus-pocus of “cognition and attribution studies”. So far, this seems to have fooled almost all of the science, media, journalists, Hollywood stars, and billionaires. Also the incoming president.

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