Remembering the Corruption of the IPCC Paleoclimate Chapter
With the economy booming and unemployment low, the Democratic Party has decided to make "Climate Change" a central feature of its 2020 campaign. Environmental fear-mongering is reaching levels not seen in the United States since the late '90s and 2000s. During that time, failed presidential candidate Al Gore tried his hand at being a movie director. His ironically-named film, An Inconvenient Truth, prominently featured the infamous "hockey stick" graph which purported to show that current levels of warmth were unprecedented in human history. The climate scientist who concocted the faulty graph, Michael E Mann (depicted) recently made headlines for himself by defending Alexandria Ocasio-Cortez and her Green New Deal proposal.
It is worth remembering who Michael Mann is, in case the Democratic Party decides to turn him into a celebrity or begins referring to him as a "leading expert" on the topic of Climate Change. Mann was the man who helped the IPCC get rid of an inconvenient truth: the historical record indicates that temperatures in the Middle Ages were warm enough that Norse Vikings were able to till the soil and produce crops in Greenland. Until the late '90s, the existence of a Medieval Warm Period was conventional wisdom among both scientists and the public. This conventional wisdom was reflected in the assessment of the first IPCC report in 1990:
"Because we do not understand the reasons for these past warming events, it is not yet possible to attribute a specific proportion of the recent, smaller warming to an increase of greenhouse gases."
This reasonable perspective on climate history severely limited the urgency with which the public viewed the human contribution to modern warming. This created a powerful incentive for climate scientists to find ways to reduce the size, scope, or importance of the Medieval Warm Period. In 1994, Malcolm K. Hughes and Henry F. Diaz used tree-ring research to claim that the Medieval Warm Period was merely a regional phenomenon. In 1995, after David Deming used boreholes to show 150 years of North American warming, a climate scientist named Jonathan Overpeck attempted to recruit him to help the IPCC "get rid of the Medieval Warm Period."
By the time the second IPCC report came around in 1995, the IPCC had changed its tune. In their view, the Medieval Warm Period could now safely be ignored because "[proxy] data prior to 1400 are too sparse to allow the reliable estimation of global mean temperature." A lack of data allowed them to come to the politically-expedient conclusion that modern warming was unprecedented:
"Based on the incomplete observations and paleoclimatic evidence available, it seems unlikely that global mean temperatures have increased by 1°C or more in a century at any time during the last 10,000 years."
After that report, the missing data that the IPCC had been looking for was produced by Michael Mann. In 1998, a team consisting of Raymond S. Bradley, Malcolm K. Hughes, and Michael E. Mann created a deeply flawed graph (MBH 98) which spliced two different datasets in order to show that the 1990s were the warmest decade since 1400.
The next year, the team extended the handle of their "hockey stick" all the way back to 1000 AD—where the data had supposedly been "too sparse" only years before—and made the Medieval Warm Period completely disappear.
In 2001, Michael Man headed the paleoclimate chapter of the IPCC's third assessment report. As lead author, Mann promoted his own work (MBH 99), thus turning the "hockey stick" into the IPCC's canonical interpretation of the last thousand years of Earth's global temperature. He used Phil Jones' and Keith Briffa's "spaghetti chart" (which use the same flawed data as Mann) and overlaid instrumental data to the graph in order to create the illusion that his hockey-stick construction was collaborated by other sources. At this point, the paleoclimate chapter of the IPCC was already reaching banana-republic levels of corruption.
After the third assessment report was published, the "hockey stick" representation of climate history went viral. Eventually, the graph was noticed by Canadian statisticians Steve McIntyre and Ross McKitrick who published a devastating critique of MBH 99. They demonstrated that Mann's methods produce hockey sticks from mere noise and also uncovered a number of problems with his data. (Two years later, McIntyre would found the blog climateaudit.org to fact-check claims by a variety of climate scientists). In 2004, two scientists named Wahl and Amman attempted to replicate the hockey stick, but only ended up proving that it fails verification statistics, which actually confirmed one of McIntyre and McKitrick's critiques).
By the time the fourth report rolled around, in 2007, Keith Briffa was made lead author of the paleoclimate chapter. He promoted his own work (the "spaghetti chart" above) as confirmation of Mann's earlier work. He also cited Wahl/Amman as independent verification of the canonical "hockey stick" interpretation of historic temperatures. This was off-the-rocker, politically-driven lunacy. Why do I bring all of this up? I am responding to this article which purports to debunk what became known as the "hide the decline" scandal. "Hide the decline" was part of the "ClimateGate" controversy where hundreds of private emails from IPCC-linked scientists were made public after a server at the Climate Research Unit was hacked. The article which supposedly debunks the scandal was retweeted by Dilbert creator, Scott Adams:
Dawson's article does not actually debunk the"hide the decline" scandal, but instead refutes one particular misinterpretation of it. When scientist Phil Jones emailed Raymond Bradley and told him that he had used "Mike's Nature Trick" to "hide the decline," he was not covering up a decrease in global temperatures. He was, instead, covering up the fact that the tree-ring proxy data were not reflecting modern temperatures. The very same tree-rings from which they extrapolated medieval temperatures were also indicating a sharp decline in temperatures in recent years. Including this data on graphs of historical temperatures diminished the "hockey stick" impression that their graphs were intended to convey, so they simply truncated the data (see the light blue line in the "spaghetti chart" above) in order to let instrumental data create the impression they desired.