Climate scientist Michael Mann's defamation trial enters closing arguments phase

Court case could hinge on 'actual malice' legal threshold

Mann's graph and the 'Climategate' allegations

Michael Mann achieved fame due to the 'hockey stick' graph he published in 1998, illustrating the rapid warming of global temperatures.

This work was picked up by a UN climate panel in 2001 and featured in Al Gore's documentary 'An Inconvenient Truth'.

However, Mann's research became subject to increased scrutiny following the 'Climategate' leaks in 2009, where his emails were published.

skeptics claimed Mann manipulated data. Mann has sued two writers for defamatory comments made following these leaks.

The defendants argue the comments were expressions of opinion

Rand Simberg, author of the original blog post, wrote:

"Mann could be said to be the Jerry Sandusky of climate science, except for instead of molesting children, he has molested and tortured data".

Mark Steyn, who referenced Simberg's article, called Mann's research 'fraudulent'.

Both have argued that their comments were protected free speech.

Actual malice legal threshold

For Mann to succeed in his lawsuit, he must prove that the writers made false and defamatory statements with actual malice. This means the defendants knew their statements were false or acted with reckless disregard for whether they were true.

This is a higher legal threshold to prove when addressing public figures.

Defamation in the age of social media

The trial comes as misinformation about climate change is widespread online.

Many scientists have paid attention to Mann's case and hope for a verdict in his favor.

Law professor Lyrissa Lidsky said:

"A jury's decision in one case about a climate scientist will not stop climate skepticism, no matter what the outcome of the trial".

This story highlights the ongoing polarization of climate change in the US.