No single artefact did more to launch the climate change scare than Professor Michael E Mann’s famous – or should that be infamous? – 1998 hockey stick graph, showing an unprecedented and sudden rise in global warming. Widely criticised on many counts it is again under fire, in a Washington courtroom drama significant for both free speech and climate science.

A 12-year defamation battle between Mann and the witty and acute conservative Canadian pundit Mark Steyn is culminating in Room 518 in D.C.’s Superior Court, after Steyn wrote a piece in National Review in 2012 referring to Mann as ‘the man behind the fraudulent climate-change “hockey stick” graph, the very ringmaster of the tree-ring circus’. Scientist blogger Rand Simberg, quoted in Steyn’s piece, is also being sued.

For those who have followed the climate-change gravy train for decades, as I have, this will be a walk down memory lane. All the old stagers are there, either listed as witnesses or mentioned in despatches – Steve McIntyre (‘human filth’, according to Mann), Roger Pielke Jnr, Ross McKittrick, ‘Mike’s Nature trick’, Climategate emails, tree rings and bristlecone pines. Even the catchy harmonies of ‘Hide the Decline’, the cult hit song by Minnesotans for Global Warming, have rung through the court.

The trial is pertinent because climate scientists have long avoided debating the science, saying it’s ‘settled’ and they don’t want to give ‘deniers’ a stage, although sceptics say that’s because the ‘settled science’ itself is so full of holes.

The evidence thus far includes jaw-dropping moments, such as when Mann declared that he had not, to his knowledge, paid one penny for his litigation involving three law firms and multiple lawyers over a dozen years. No such luck for Steyn, and Mann’s dark money donors remain unknown. The graph was first published in Nature magazine in 1998, starred in the 2001 IPCC report and became the poster child for global warming alarmism; it’s foundational to the IPCC’s climate-change case, so there are plenty of deep-pocketed left-leaning vested interests at stake.

The trial is occasionally rollicking and hilarious, given Steyn’s theatricality and turn of phrase, but also ugly. The court has heard of Mann’s abuse against ‘deniers’ (his preferred term) as evidenced in emails and Twitter posts – no playing the ball for Mann. In one email to a Wikipedia editor, with Nasa scientist Gavin Schmidt copied in, Mann accused climate scientist Judith Curry of engaging in an affair with a married academic while a student. ‘Sleeping her way to the top’, as the defence lawyer characterised it. In fact, she was on university staff and the colleague had separated from his wife; Mann had to admit that his gossip was false. He was only human, he said. Those who cherish science as a noble endeavour need to remember that those who practise it are ordinary humans, and sometimes very ordinary. But don’t take it from me – check out Mann’s long history of belittling Twitter posts for yourself.

One is tempted to see Mann’s abuse as par for the behavioural course from a scientist who frequently and falsely claimed to have won a Nobel prize, even after the Nobel committee said he had not. The court heard Mann was the only person the Nobel committee had ever asked to stop claiming to be a Nobel winner.

As the litigant, Mann must prove he suffered damages. No witnesses so far have been led to testify to his career suffering. His salary has risen, he has jet-setted to many international climate events, published a number of books and rubbed shoulders with the Clintons and Leonardo DiCaprio, as is typical of the climate glitterati. Much time was spent on his suffering ‘a mean look’ in his local supermarket from a stranger, and he claims his grant applications failed precipitously after the alleged defamation. However, Penn State had been hit by a child rape scandal around the same time, involving high-profile football coach Jerry Sandusky, who was ultimately jailed, and even the university’s president was charged, convicted and jailed, having tried to hush the crimes; that may have dried up the money flow. The two cases are connected by Steyn and Simberg’s claim that a corrupt Penn State tried to sweep both issues under the carpet, to protect their stars, and brand.

Further emails read to the court have hinted at Mann’s motivation; he hoped to ruin both National Review and Steyn himself, ‘this odious excuse for a human being’.

The case necessarily touches on climate science. I was curious to hear how Mann explained the use of two different temperature sets to create the hockey stick, the first one from tree-ring proxies dating back to the 1100’s, showing flat temperatures and switching to the second record, using modern thermometers, in the 20th century to get the final uplift of the hockey stick ‘blade’. Seemingly the proxies had become unreliable in the 20th century around the point when they contradicted the thermometer record. This at the time reportedly prompted even Phil Jones of the East Anglia University’s Climatic Research Unit to complain that Mann was comparing apples and oranges. Well, yes. In court, Mann had no explanation for why the tree-ring data became unreliable in the 20th century, it just had, he averred. It didn’t seem to occur to him that perhaps it was always unreliable, given that the graph had also erased the well-attested medieval Warm Period.

It has also emerged that Mann’s Ph.D expertise is in geology, not in statistics. Nor did he consult a statistician over the creation of the hockey stick graph, which Mann compiled from tree-ring data gathered by two climatologists; in court he admitted his original calculations were ‘pretty crude’.

(A note: I am taking much of my information from the podcast Climate Change on Trial, a daily enactment and account by awarded journalists Ann McElhinny and Phelim McAleer. There is little mainstream reporting; if the podcasters err, so will I.)

Given the vindictive USD$83 million damages found against Trump in his case against serial rape accuser E. Jean Carroll, one cannot be optimistic about any jury trial in deep blue Washington DC. But Steyn is going down fighting, and one cannot but admire his guts and brio, even if his bank balance has been cleaned out. Sadly Steyn, representing himself, is now in a wheelchair, having recently suffered three heart attacks. If ever there were a case deserving funding, it is his. The trial continues.