FILM
AN INCONVENIENT SEQUEL: TRUTH TO POWER ★★★

(PG) Selected cinemas (100 minutes) 

It's been a little over a decade since the release of former US vice president Al Gore's famous lecture-documentary An Inconvenient Truth – the film which made us all rethink our habits of consumption and prompted a worldwide shift to clean energy, bringing global warming to a standstill overnight.

Just kidding. Greenhouse gas emissions from the burning of fossil fuels, while not rising as fast as previously, continue at a steady rate. The last three years have been the hottest on record, with oceans warming even faster than studies anticipated. Polar ice caps are shrinking rapidly, extreme weather events becoming ever more common, and we're entering into what scientists are describing as Earth's "sixth mass extinction".

As Gore's South Park namesake Big Gay Al once sang: "The whole world's gone to hell, but how are you?" In one sense at least, Gore is flourishing – as a revered public spokesman for a cause which needs all the publicity it can get. Since An Inconvenient Truth took off, he's been on his own version of Bob Dylan's never-ending tour, presenting his famous slideshow around the planet and holding climate leadership workshops enabling others to do the same.

This activity is the subject of Bonni Cohen and Jon Shenk's​ An Inconvenient Sequel: Truth to Power which, like its predecessor, is more agitprop than objective journalism, though Cohen and Shenk don't have to strain too hard to make their subject look impressive. The film proceeds in the traditional concert documentary manner, combining extracts from the slideshow itself with glimpses behind the scenes: these show Gore as not just a passionate speaker but an expert negotiator, especially during the film's climax at the 2015 Paris climate talks.

Though the point isn't laboured here, one key to Gore's drive is clearly his not unwarranted belief that he would have won the 2000 US presidential election had every vote been properly counted. To miss out like this would be a traumatic experience for anyone – and if he's embarked on his crusade partly as a means of psychological renewal, this seems about the best decision possible under the circumstances.

The Gore of today is unquestionably a man of conviction, which may help explain why he has become a warmer, more personable screen presence than he used to be. The stock line about him during his political career was that he was wooden, and there's still something of the uncanny valley about his slow delivery, rehearsed one-liners and crafted hand gestures. But the stiffness is part of the charm, aligning him with a distinctly American archetype that retains a wide appeal: the slightly bumbling, cornball dad who's steely when he needs to be.

Gore's willingness to put himself out there means his enemies will never have a shortage of ammunition. An Inconvenient Truth was caught in a handful of factual errors, and it's very possible this will happen again with the sequel. Certainly, we'll continue to hear the complaint that Gore's globetrotting lifestyle undercuts his message – the most tedious kind of ad hominem argument, leaving aside the question of how far his trips are "offset". On a more serious level, it's been pointed out that he avoids certain issues, such as the relative carbon footprints of meat-eaters and vegetarians, though he himself became a vegan a few years back.

There's also the question of Gore's optimism, which is surely sincere but also a deliberate choice, guided by long practice in selling a message to the public. In the face of grim reality, it's hard to find his stance completely persuasive; but equally, his example forces the question of whether anyone can afford the luxury of despair.