Rishi Sunak has promised the UK's global leadership on fighting climate change will continue after its COP presidency ends - ahead of the prime minister attending the summit after a U-turn.
Mr Sunak was speaking at a gathering of world leaders, business figures, environmentalists and NGOs at Buckingham Palace ahead of the COP27 climate summit in Egypt.
He will be heading to the Red Sea resort of Sharm El-Sheikh on Sunday for the summit, which runs from 6-18 November, after being forced into a U-turn by environmental campaigners and MPs on Wednesday.
The prime minister previously said he would not be attending due to "other pressing domestic commitments".
But he has now thrown himself fully behind the summit, kicking it off by telling a reception hosted by King Charles the world will experience "more human suffering" if we continue to allow "climate change to ravage our planet".
The King will miss the gathering after a "unanimous agreement" was made during Liz Truss's brief premiership he should not attend following advice from his office.
The new monarch has been a long-time campaigner on environmental issues and last autumn told the COP26 talks in Glasgow the world has had enough of talking, and commitments needed to be put into practice.
Speaking in the Buckingham Palace ballroom on Friday, Mr Sunak said: "As recent events have shown, delivering on the promise of Glasgow is more important than ever.
"More important because, as we have seen so starkly with the war in Ukraine, it is vital to invest in secure, renewable sources of energy and sustainable food production.
"More important because every moment we allow climate change to ravage our planet we will see more human suffering like the devastating floods in Pakistan.
"And more important because if we do not act today, we will risk leaving an ever more desperate inheritance for our children.
"The UK's presidency may be coming to an end, but our global leadership will continue."
COP26 President Alok Sharma will be handing over the UK's presidency to Egypt at the summit and has said he would "welcome" the King's presence at COP27.
The US special envoy on climate change, John Kerry, who was also at the palace on Friday, told Sky News it would be "very powerful" if the King was in Egypt.