Sir David Attenborough will try again later this year to convince world leaders that immediate climate action is vital.
Sir David has been named the “people’s advocate” at the COP26 summit, to be held in Glasgow in November.
As part of the role, the 95-year-old will address political leaders about why action is needed to prevent the catastrophic consequences of climate change.
In a short video message, he said: “I am greatly honoured to be given the role of people’s advocate.
“There could not be a more important moment that we should have international agreement.
“The epidemic has shown us how crucial it is to find agreement among nations if we are to solve such worldwide problems. But the problems that await us within the next five to 10 years are even greater.
“It is crucial that these meetings in Glasgow, COP26, have success, and that at last the nations will come together to solve the crippling problems that the world now faces.”
He will also make a speech at the G7 leaders’ summit in Cornwall next month.
Prime Minister Boris Johnson said: “Sir David Attenborough has already inspired millions of people in the UK and around the world with his passion and knowledge to act on climate change and protect the planet for future generations.
“There is no better person to build momentum for further change as we approach the COP26 climate summit in November. I am hugely grateful to Sir David for agreeing to be our people’s advocate.”
COP26 president-designate, Alok Sharma, said: “Climate change is the greatest threat facing humanity and the stakes could not be higher for our planet.
“The next decade will be make, or break, for cutting global emissions sufficiently to avoid the worst effects of climate change.
“That is why I am delighted to be working with Sir David, a hero for our country and our planet, to inspire action ahead of COP26.”
Sky News has launched the first daily prime time news show dedicated to climate change.
The Daily Climate Show is broadcast at 6.30pm and 9.30pm Monday to Friday on Sky News, the Sky News website and app, on YouTube and Twitter.
Hosted by Anna Jones, it will follow Sky News correspondents as they investigate how global warming is changing our landscape and how we all live our lives.
The show will also highlight solutions to the crisis and show how small changes can make a big difference.