I was sceptical when I went to see Al Gore deliver his first PowerPoint presentation on global warming in 2005. I had heard good things, but couldn't shake this image of Gore as a smart but stone-faced US politician who fumbled his words and had to be told to dress in earth tones. Instead, what I encountered at Harvard University was a dynamic speaker who had transformed a complex topic into an accessible and generally fair presentation, which he delivered with passion and a healthy dose of humour. If this Gore had run for president, I thought, he could have changed history. Six years later, on 14 September, I tuned in to Gore's spectacularly ambitious attempt at a sequel with a similar mixture of curiosity and trepidation, only this time my fears were confirmed.

The former US vice president's 24 Hours of Reality kicked off in Mexico City and then followed the Sun around the world with a series of rallies in multiple languages, all of which were webcast and translated into English. In keeping with the model of training a small army of presenters to expand Gore's reach, at the centre of each rally was a single PowerPoint presentation highlighting floods, storms, landslides and fires that have wreaked havoc around the world over the past year (G. Beattie, Nature Clim. Change 1, 372–374 2011). The presentation sought to reinforce the link between extreme weather and global warming, to give a sense of urgency to a long-term problem and, most importantly, to put a face on the issue. “The climate crisis isn't a political problem,” Gore said in kicking off the event. “It's a human problem.”

Broadcasting disaster: 24 Hours of Reality showed images of extreme weather events, including floodwater incursions in Brazil, as evidence for the impact of climate change around the world. Credit: © VLADIMIR PLATONOW/AGÊNCIA BRASIL VIA WIKIMEDIA COMMONS

It's an interesting idea with honest intentions, and at a gut level it was effective. How could one not feel for the Brazilian woman who had had to put her faith in a rope and jump off her own roof into a muddy torrent that washed her home away moments later? And how could one not be angry, after realizing the simplicity of the physical argument — more heat equals more water vapour equals more intense storms — linking that flood to global warming? What's more, we have a culprit for the crime: high rollers who deal in fossil fuels and question simple science just like Big Tobacco did a few short decades ago. “We've seen this before,” I heard the interpreter say as renewable energy businessman Gerardo Pandal delivered the opening presentation in Mexico City.

It's a dramatic tale, but the most powerful images are also the weakest link. Many scientists are increasingly willing to link global climate change to local weather extremes, but some are not. Regardless, such connection would not mean global warming is now responsible for all extreme weather. A week before Gore's event, the US National Oceanic and Atmospheric Administration reported that a common Pacific Ocean trend known as La Niña probably contributed to many of the same events Gore cited — flooding in Australia, drought in eastern Africa, and both drought and flooding in the United States. Although these nuances were discussed at various points during scientific panels in between the events, Gore's presentation itself didn't mention La Niña, nor did it acknowledge recent research suggesting that global warming need not be invoked to explain last year's fires in Russia.

But in many ways, the problem is with the message itself. Gore's goal is not to disseminate science so much as to cultivate an idea. Maybe that idea is fresh in many parts of the world, maybe viewers in Tonga felt inspired. But the issue of global warming became politicized long ago at home. Gore may have briefly pumped up his disillusioned environmental base, but it's hard to imagine such a polarizing figure convincing anybody who has honest doubts about the severity of the problem, let alone the diehard sceptics.

I dropped in periodically over the course of the 24 hours, so that by the time Gore himself took the stage I knew the presentation quite well. His talk felt forced, and it occurred to me that I was watching the same Gore who lost the election in 2000. I couldn't help but anticipate him when he compared climate deniers to the tobacco industry. I've seen this before, I thought, in three languages no less. In the end, I found myself paying more attention to the live chat stream posted on the web page. After Gore finished up, the compliments flew. “That was amazing!!!!!!” “Bravo! Bravo! Bravo!” Then this popped up: “I'm bored, are you?” Yes.