Superfact 26: The disputed Hockey Stick Graph showing that recent global warming is unprecedented in the context of the past thousand years has been shown to be correct.
The Mann, Bradley, and Hughes hockey stick curve published in 1998 in Nature and showing a sharp upturn in global temperatures in recent years as well as relatively flat temperatures in the previous 1,000 years, ignited a firestorm.
Initially some scientists criticized it for being wrong, and the rightwing media and think tanks, and especially politicians criticized the graph and even attacked the scientists involved accusing them of being frauds. Al Gore was harshly criticized for using the hockey stick in his documentary “an inconvenient truth”. There were congressional hearings, politicians intimidating scientists, fake scandals, threats, and lawsuits.
The propaganda campaign against the hockey stick graph succeeded in winning over the public and that included me. I was for the longest time convinced that the hockey stick graph was wrong and perhaps a fraud. I was wrong. I had been bamboozled just like large segments of the American public.
The scandal around the hockey stick curve and the related climate-gate (fake scandal) was used to question the entire concept of global warming / climate change. As you may know, the evidence clearly shows that global warming is happening and is caused by us.
It should be noted that the way Mann, Bradley, and Hughes implemented their statistical analysis was not 100% correct, but the discrepancy was very small and did not make a big difference. However, this discrepancy was very useful for their detractors.
The controversy led to an investigation resulting in the so-called North Report. The 2006 North Report published by the United States National Academy of Sciences endorsed the MBH studies with a few reservations.
Subsequent research has resulted in more than two dozen reconstructions, using various refined statistical methods and combinations of proxy records. They are not identical to the original hockey-stick graph but closely resemble it and consistently show a slow long-term cooling trend changing into relatively rapid warming in the 20th century.
Since there is now a scientific consensus supporting the hockey stick graph, it is important news, and a lot of people still have not gotten the memo or are refusing to believe it, I consider it a super fact.
Before The Hockey Stick Graph
Before the hockey stick curve there was a lot of talk about the medieval warm period and the little ice age. Many people used these periods to cast doubt on global warming claims by scientists. I should say that the climate scientists claim about global warming was not based on the temperature record for the last 1,000 years. It was because the observed recent uptick in average global temperatures was not expected naturally.
Their worries were based on the fact that our greenhouse gas emissions could explain the uptick whilst there was no climate cycle or natural phenomenon that could explain it. That combined with the fact that the manner in which the warming was happening (it’s fingerprint if you will) showed that it was our greenhouse gases causing it.
So, the comparably high temperatures during the medieval warm period and the very cold temperatures during the little ice age should not have mattered much. But as you can see in the graph below, the old temperature graphs could be used by global warming skeptics.
It should be noted that previous estimates for the temperatures during the medieval warm period and the little ice age were based insufficient data and guesstimates.
The graph below from the 1990 IPCC report shows three curves, a red, a blue and a black one, and a green extension to the blue from 1998 to 2007. The red graph shows a large bulge corresponding to the medieval warm period, a significant drop corresponding to the little ice age, and a minor uptick in recent temperatures. The blue curve shows a flattened medieval warm period with only a minor little ice age and sharper uptick in recent temperatures. The green extension stretching from 1998 to 2007 shows a significantly sharper uptick in temperatures. The black curve is an alternative temperature curve by Moberg.
As you can see the estimates for the average global temperatures during the medieval warm period and little ice age were too large. When the hockey stick curve came along (next graph), a propaganda tool was diminished, which led to the media storm.
Multiple Hockey Stick Graphs
As mentioned, various refined statistical methods and combinations of proxy records, has resulted in another couple of dozen hockey stick curves that largely agree with the original MBH hockey curve. Below are a few examples taken from various sources. The first two graphs below are taken from the real climate website, a website created by climate scientists.
IPCC 3rd Assessment Report
Eight Hockey Sticks by New Scientist
The graphics below are focused on the northern hemisphere. The top graph shows the 2001 IPCC hockey stick curve with data from thermometers (in red). Below that graph are eight more hockey stick curves plus a red dotted line corresponding to the instrumental record. This was compiled for New Scientist by Rob Wilson of the University of Edinburgh, UK.
The Hockey Stick Wars
I also wanted to add a few examples related to the propaganda wars against the first hockey stick graph and its author Dr. Michael Mann and climate science in general. If you haven’t followed this topic, I can add that it did get intense.
On April 23, 2010, Virginia Attorney General Ken Cuccinelli issued a Civil Investigative Demand (CID) to the University of Virginia (UVA). The CID demanded that UVA provide every email, record, or document it had related to Dr. Mann from his time there from 1999 to 2005. This resulted in a strong reaction from the scientific community.
On 2 March 2012 the Supreme Court ruled that Cuccinelli as Attorney General had no legal authority to demand the records from the university. Dr. Mann was also severely harassed and received chilling death threats against himself as well as his family, as documented in his book “The Hockey Stick and the Climate Wars: Dispatches from the Front Lines”.
In February 2024, Michael Mann won a defamation lawsuit against conservative writers Rand Simberg and Mark Steyn (Mann v. Competitive Enterprise Institute). The jury awarded Mann $1 million in punitive damages and $1 in compensatory damages. The lawsuit was over blog posts written by Simberg and Steyn that accused Mann of manipulating data in his famous “hockey stick” graph. It was not so much about questioning the science but rather about the fact that they intentionally tried to ruin his reputation using false information.
For example, they were comparing him to the infamous pedophile Jerry Sandusky. Jerry Sandusky was a football coach at Penn State University and Dr. Michael Mann is a distinguished Professor of Atmospheric Science at Penn State.
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