After six years of tedious litigation, a court in Vancouver, British Columbia appears set to hand down a ruling involving one of the most controversial claims ever made in support of human-induced global warming.

The case pits two climatologists – Michael Mann of Pennsylvania State University and Tim Ball, retired from the University of Winnipeg – in a dispute rooted in data Mann used in creating his famous, or infamous, “hockey stick” graph. In 1999, Mann was the lead author of a paper that used an assortment of statistical techniques to reconstruct variations in atmospheric temperatures over the past 1,000 years. The graph made the Medieval Warm Period all but disappear and showed a sharp spike in temperatures at the end of the 20th century that resembled the blade of a hockey stick.

Mann was one of eight lead authors of the “Observed Climate Variability and Change” chapter in the United Nations Intergovernmental Panel on Climate Change (IPCC) Third Scientific Assessment published in 2001. A graph based on Mann’s work was highlighted throughout the IPCC report. It received widespread publicity and was touted by climate alarmists as further evidence of manmade global warming. Indeed, Mann’s hockey stick took on a life of its own and was repeatedly cited by the IPCC and numerous governments as justifying collective action to combat climate change. The hockey stick has also been cited in innumerable peer-reviewed papers on climate change.

“Secret Science”

Astounded by the sudden disappearance of the Medieval Warm Period — a time generally considered to have been warmer than the present — a growing chorus of critics demanded to see the underlying data on which the hockey-stick graph was based. Mann and his co-authors refused to release the data, even though their paper had been funded by U.S. taxpayers. The episode raised allegations that climate alarmists were engaging in “secret science.”

One of those critics was Tim Ball. In a 2011 interview, he quipped that Mann “should be in the State Pen, not Penn State.” Mann sued Ball for defamation in British Columbia under a procedure known as a Strategic Lawsuit Against Public Participation (SLAPP). SLAPP lawsuits are intended to censor, intimidate, and silence critics by threatening them with the cost of a legal defense until they abandon their criticism.

As the case unfolded, the BC Supreme Court directed Mann to turn over all data relating to his graph by Feb. 20, 2017. The deadline came and went without the data being handed over by Mann.

Ball believes that Mann’s refusal to disgorge the data by the court-ordered deadline has put the Penn State researcher in a precarious legal position. As Ball explains (

We believe that he [Mann] withheld on the basis of a US court ruling that it was all his intellectual property. This ruling was made despite the fact the US taxpayer paid for the research and the research results were used as the basis of literally earth-shattering policies on energy and environment. The problem for him is that the Canadian court holds that you cannot withhold documents that are central to your charge of defamation regardless of the US ruling.”

Mann’s Suit Against Mark Steyn

Once the BC Supreme Court has ruled in his suit against Ball, Mann will have another legal battle on his hands. Mann filed a SLAPP lawsuit in Washington, D.C. against writer and commentator Mark Steyn after the latter wrote in a 2011 National Review Online article that Mann “has perverted the norms of science on an industrial scale.” Judith Curry, a recently retired climatologist at Georgia Tech, has submitted to the court an Amicus Curiae brief critical of Mann’s scientific methods.

For his part, Ball has produced his own graph showing temperature variability over the past 1,000 years. Both the Medieval Warm Period and the following Little Ice Age can be seen on the graph. The graph also shows the gradual warming since the Little Ice Age, albeit to levels below what was experienced during the Medieval Warm Period. Unlike Mann, Ball has published the data on which his graph is based.