"An Inconvenient Sequel: Truth to Power" received a special screening at Cannes after premiering at the Sundance film festival in January.
"An Inconvenient Sequel: Truth to Power" received a special screening at Cannes after premiering at the Sundance film festival in January, a decade after Gore's first documentary warned of environmental catastrophe.
Today, the White House is occupied by a man who has called global warming a "hoax" perpetrated by China, wants to encourage US coal production and vowed to reverse fossil-fuel curbs imposed by his predecessor, Barack Obama.
But Gore said there were few reasons for pessimism, arguing that hard economic reality now weighed heavily in favour of climate activism.
Smarter technology means cleaner energy increasingly makes better economic sense than fossil fuels -- a formula endorsed by hundreds of billions of dollars of investment.
"We now know after four months of the Trump administration that no one person, not even a president, can stop the climate movement," Gore told reporters in Cannes.
"We have seen large states like California and New York and many others now making faster progress than the commitments made by former president Obama during the Paris Agreement."
Gore repeated his optimism that the US will stay in the 2015 landmark agreement to curb global warming, despite Trump's campaign promise to "cancel" it.
"I do believe there is a better-than-even chance that he will surprise many by keeping the US in the Paris Agreement," Gore said.
Uncertainty over the position of the United States, the world's second biggest carbon emitter, has cast a long shadow over the 196-nation Paris accord.
Divisions are reported to have emerged within the Trump administration over the political cost of abandoning the pact.
The deal is strongly supported by Europe and China as well as by vocal US lobbies for the environment and cleaner technology.
Trump will "not be making an announcement regarding that agreement" until his return to Washington after the G7 summit in Sicily on Friday and Saturday, the White House said on May 9.
"An Inconvenient Sequel" comes 11 years after the original, which won two Oscars, took $50 million (44.5 million euros) at the box office and helped propel Gore to the Nobel Peace Prize, which he co-won in 2007 with the UN's panel of climate scientists.
As before, it points to extreme droughts, record-breaking downpours and melting Arctic ice as evidence of climate change, but has a more hopeful message than before.
- 'Solutions now'
"The exciting new reality depicted in this film is that in a growing number of areas around the world, it is now cheaper to get electricity from the sun and the wind... than it is to continue using the dirty, polluting fuels of the past."
He added: "We have the solutions now, and the remaining task is to summon the political will to implement these solutions quickly enough."
Gore suggested that in the era of fake news, cinema might have a better chance of persuading people.
"Film as a long-form medium now is the premier way to deliver a powerful message with integrity that the world needs to hear.
"It may be in part because the news environment is so chaotic and messy now," he said.