Sir David Attenborough has issued his strongest statement yet on the threat posed to the world by climate change.
In the BBC programme Climate Change - The Facts, the veteran broadcaster outlined the scale of the crisis facing the planet.
Sir David said we face "irreversible damage to the natural world and the collapse of our societies".
But there is still hope, he said, if dramatic action to limit the effects is taken over the next decade.
Sir David's new programme laid out the science behind climate change, the impact it is having right now and the steps that can be taken to fight it.
"In the 20 years since I first started talking about the impact of climate change on our world, conditions have changed far faster than I ever imagined," Sir David stated in the film.
"It may sound frightening, but the scientific evidence is that if we have not taken dramatic action within the next decade, we could face irreversible damage to the natural world and the collapse of our societies."
Speaking to a range of scientists, the programme highlighted that temperatures are rising quickly, with the world now around 1C warmer than before the industrial revolution.
"There are dips and troughs and there are some years that are not as warm as other years," said Dr Peter Stott from the Met Office.
"But what we have seen is the steady and unremitting temperature trend. Twenty of the warmest years on record have all occurred in the last 22 years."
The programme showed dramatic scenes of people escaping from wildfires in the US, as a father and son narrowly escape with their lives when they drive into an inferno.
Scientists say that the dry conditions that make wildfires so deadly are increasing as the planet heats up.
Some of the other impacts highlighted by scientists are irreversible.
"In the last year we've had a global assessment of ice losses from Antarctica and Greenland and they tell us that things are worse than we'd expected," said Prof Andrew Shepherd from the University of Leeds.
"The Greenland ice sheet is melting, it's lost four trillion tonnes of ice and it's losing five times as much ice today as it was 25 years ago."
These losses are driving up sea levels around the world. The programme highlights the threat posed by rising waters to people living on the Isle de Jean Charles in Louisiana, forcing them from their homes.
"In the US, Louisiana is on the front line of this climate crisis. It's losing land at one of the fastest rates on the planet - at the rate of of a football field every 45 minutes," said Colette Pichon Battle, a director of the Gulf Coast Center for Law & Policy.
"The impact on families is going to be something I don't think we could ever prepare for."
Sir David's concern over the impacts of climate change has become a major focus for the naturalist in recent years.
This has also been a theme of his Our Planet series on Netflix. His new BBC programme has a strong emphasis on hope.
Sir David argues that if dramatic action is taken over the next decade then the world can keep temperatures from rising more than 1.5C this century. This would limit the scale of the damage.
"We are running out of time, but there is still hope," said Sir David.
"I believe that if we better understand the threat we face the more likely it is we can avoid such a catastrophic future."
The programme said that rapid progress is being made in renewable energy, with wind now as cheap as fossil fuels in many cases. It shows how technologies to remove and bury carbon dioxide under the ground are now becoming more viable.
But politicians will need to act decisively and rapidly.
"This is the brave political decision that needs to be taken," said Chris Stark from the UK's Committee on Climate Change.
"Do we incur a small but not insignificant cost now, or do we wait and see the need to adapt. The economics are really clear on this, the costs of action are dwarfed by the costs of inaction."
The programme also highlights the rising generation of young people who are deeply concerned about what's happening to the planet.
Swedish teenager Greta Thunberg explained that things can change quickly, despite the scale of the challenge on climate change.
"The first day I sat all alone," she said, speaking of her decision to go on strike from school and sit outside the Swedish parliament to highlight the climate crisis.
"But on the second day, people started joining me... I wouldn't have imagined in my wildest dreams that this would have happened so fast."
"Change is coming whether you like it or not."
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Climate Change - The Facts was on BBC One on Thursday 18 April at 9pm and is available on iPlayer.