Boris Johnson has warned world leaders that they will be judged with “bitterness and resentment” by future generations if they fail to tackle global warming.

Addressing world leaders at Cop26, including US president Joe Biden, India’s Narendra Modi and German chancellor Angela Merkel, the Prime Minister said that while the technology existed to cut rising emissions, the question was whether they had the will to deliver.

He reminded them that while their average age was over 50, they would be judged by a world population – half of whom were under 30.

“The children who will judge us are children not yet born, and their children.

“We are now coming centre stage before a vast and uncountable audience of posterity and we must not fluff our lines or miss our cue.

They will judge us with bitterness and with a resentment that eclipses any of the climate activists of today and they will be right.

“Because if we fail, they will not forgive us – they will know that Glasgow was the historic turning point when history failed to turn.

“They will judge us with bitterness and with a resentment that eclipses any of the climate activists of today, and they will be right.”

Mr Johnson warned of the dangers of rising temperatures, jeopardising food supplies for hundreds of millions of people, more wildfires and eventually the loss of whole cities such as Miami, Alexandria and Shanghai.

“The longer we fail to act and the worse it gets and the higher the price when we are forced by catastrophe to act,” he said.

Coining a phrase from activist Greta Thunberg, he warned that the promises to limit global temperature rises under the Paris Agreement would be “nothing but blah blah blah”.

And the anger and impatience of the world would be “uncontainable” unless Cop26 was the moment leaders got real about climate change, he said.

Channelling his hero Sir Winston Churchill, Mr Johnson said: “While Cop26 would not be the end of climate change, it can and it must mark the beginning of the end.”

Mr Johnson took to the stage to make his speech after the delegates watched a performance by Skye piper Brighde Chaimbeul, a video narrated by Brian Cox and a poem by Yrsa Daley-Ward composed for Cop26.

Around 120 heads of state and government are attending the world leaders’ summit at the start of the Cop26 talks, where countries are under pressure to increase action in the next decade to tackle dangerous warming.

UN Secretary-General Antonio Guterres told the Cop26 summit the world’s “addiction to fossil fuels is pushing humanity to the brink”.

He told the opening plenary of the conference in Glasgow: “We face a stark choice: either we stop it — or it stops us.”

He warned the “sirens are sounding”, and said: “Our planet is talking to us and telling us something. And so are people everywhere. Climate action tops the list of people’s concerns, across countries, age and gender.

“We must listen — and we must act — and we must choose wisely. On behalf of this and future generations, I urge you: Choose ambition. Choose solidarity. Choose to safeguard our future and save humanity.”

We need a vast military-style campaign to marshal the strength of the global private sector.

And the Prince of Wales called for the world to be on a “war-like footing” to tackle climate change.

He said: “We know this will take trillions, not billions, of dollars. We also know that countries, many of whom are burdened by growing levels of debt, simply cannot afford to ‘go green’.

“Here, we need a vast military-style campaign to marshal the strength of the global private sector. With trillions at its disposal – far beyond global GDP and, with the greatest respect, beyond even the governments of the world’s leaders – it offers the only real prospect of achieving fundamental economic transition,” Charles urged.