Last week, a retired physics professor called Nick Cowern said it was time to get tough with ‘climate denialists’. ‘In my opinion the publication of climate disinformation should be a criminal offence,’ he posted on Twitter. He was ridiculed, but what sounds ludicrously over-the-top today could easily become the norm tomorrow. At least four EU member states have made it a criminal offence to spread disinformation – Hungary, Lithuania, Malta and France – and others including Ireland are preparing to do the same. In the UK, the Online Safety Bill will introduce a new false communications offence.

I have a dog in this fight since I run a news publishing website that’s frequently accused of spreading false information about climate change. Scarcely a week goes by without a fact-checking agency concluding that an article we’ve published – often by Chris Morrison, the environment editor – is false or misleading. If support for free speech continues to deteriorate, it’s possible that in about five years I’ll be found guilty of ‘denialism’ and sentenced to hard labour.

One of the problems with criminalising ‘climate disinformation’ is there’s no infallible authority the courts could rely on to determine whether a particular claim about something climate-related is true or false. Advocates of net zero and other measures designed to reduce carbon emissions often use the term ‘climate deniers’ to describe their opponents, thereby persuading themselves that proving them wrong would be easy. But even the most hardened sceptics wouldn’t dispute that average global temperatures have increased in the past 150 years. Rather, the argument is about the role of human activity, such as the burning of fossil fuels, in global warming and how much impact changing our behaviour would have. We also dispute just how catastrophic rising global temperatures are, and are unimpressed by the hyperbole of the environmental lobby (‘global boiling’). In other words, proving us wrong isn’t as straightforward as pointing to temperature data.

I suppose the prosecution could summon distinguished climate scientists as expert witnesses, but then so could the defence – for instance Dr John Clauser, last year’s joint winner of the Nobel Prize for Physics, who’s just signed a declaration stating there is no climate emergency. No doubt the would-be jailers would invoke the ‘97 per cent of scientists agree’ canard, but not only is that stat dubious, it’s also a non-sequitur. As Einstein said when 100 physicists published a book rubbishing his theory of relativity: ‘Why 100? If I was wrong, one would have been enough.’

Perhaps Exhibit A for the prosecution would be a ‘fact check’ by a reputable news organisation. Last year Reuters took issue with a piece by Chris Morrison in which he noted that Arctic sea ice was making a comeback and the coverage was well above a 2012 low point. This was said to be ‘misleading’, although the figures came from an official EU weather source. Reuters’ experts said that the sea ice was not recovering, pointing to a declining trend over a longer time period. One of them didn’t dispute the ice had recovered since 2012, but said it was a ‘wiggle’ and should not be cited as evidence that ‘climate change isn’t real’, which Chris hadn’t claimed. Nevertheless, he was accused of ‘cherry-picking’, although the sea ice improvement continues to this day. Send him down m’lud.

Or maybe not. I doubt the evidence of an ‘independent fact-checker’ would be taken as gospel by a jury. A defence barrister could ask them during cross-examination why they never scrutinise the statements of climate alarmists like Greta Thunberg. Last week, she pulled out of the Edinburgh International Book Festival, claiming the sponsor, Baillie Gifford, ‘invests heavily in the fossil fuels industry’. But wasn’t that a tad ‘misleading’? A spokesman for Baillie Gifford says just 2 per cent of its clients’ money is invested in companies with businesses related to fossil fuels. But assertions such as Greta’s, along with her pretence that western governments have done ‘nothing’ to tackle climate change, are never fact-checked.

Setting aside the difficulty of securing convictions, what would be the point of criminalising ‘climate disinformation’? History teaches us that you cannot legislate against ‘fake news’. Far from stopping its spread, it just adds to its allure. As the Supreme Court Justice Louis Brandeis said, the best way to counter what you think of as false speech is not enforced silence but more and better speech. If Nick Cowern is so sure he’s right, he shouldn’t be afraid to debate the ‘climate denialists’ in the public square.