John Kerry has warned President-elect Donald Trump not to make any “irrevocable choices” before he has the chance to see for himself the devastating impact of man-made climate change.

The US Secretary of State’s arrival here at the UN climate summit in Marrakech brought with it a clear sense of urgency - as if it was dawning on delegates that they have little more than two days left to save the world from the looming threat of a Trump administration.

In his much-awaited address, the last he will give to a UN climate summit in his current capacity, Mr Kerry reached for the strongest language possible in a setting such as this, warning that a failure to tackle climate change would be a “moral failure, a betrayal of devastating consequences”.

But he also continued a theme that has emerged at the talks so far by failing to mention Mr Trump by name. It is as though some delegates hope that by ignoring the orange-tinted elephant in the room, he will simply go away.

Mr Trump is seemingly such a threat to these talks because he has previously described climate change as a hoax perpetrated by the Chinese, repeatedly questioning the scientific evidence for man-made global warming.

And the President-elect has specifically threatened to “cancel” the Paris Agreement, the plan for action to limit global temperature rises that has been ratified by 110 countries - including the US.

There was no mistaking the target of Mr Kerry’s keynote address on Wednesday afternoon, as he warned that the “overwhelming majority” of Americans were aware of the threat of climate change and praised the Paris deal as “built to last”. “We have to continue the fight,” he said.

Climate change: It's "game over" for planet earth

The closest he came to addressing Mr Trump directly came when he urged: “For those in power in all parts of world including my own, I ask you: see for yourself before making irrevocable choices.”

He said: "No one has the right to make decisions that affect billions of people based solely on ideology or without proper input“.

Moments before Mr Kerry’s speech, President Barack Obama was speaking on a state visit to Greece. He too refused to mention Mr Trump by name.

Climate activists admit there is still something of an air of disbelief to the conference, a week after their worst fears were realised at the US ballot box.

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Avipsa Mahapatra, from the Environmental Investigation Agency (EIA) campaign group, told The Independent that delegates were being “cautious” - hoping that if Mr Trump is not provoked too much, his newfound “politeness” since winning the election can be converted a full-blown change of heart.

“Right now he is still just President-elect - so it is tricky to talk about [a Trump administration] while there are no clear policies. We have to wait and watch what kind of Trump we get as president.

“After spending so much effort getting here, we don’t want to believe it could all fall apart,” she added.

But not everyone is refusing to tackle the issue of the US President-elect head on. In a joint letter revealed at a press conference at the summit, 366 American businesses and investors urged Mr Trump to see the financial sense behind supporting green initiatives.

Addressed to Mr Trump and speaking in a language that they hope he will understand, the business leaders warned that “failure to build a low-carbon economy puts American prosperity at risk”.

“Implementing the Paris Climate Agreement will enable and encourage businesses and investors to turn the billions of dollars in existing low-carbon investments into the trillions of dollars the world needs to bring clean energy prosperity to all,” the letter read.

A dozen Fortune 500 firms were among the signatories, and brands represented included Mars, Hewlett Packard, Hilton and General Mills.

Matt Patsky, CEO of Trillium Asset Management, said virtually every Fortune 500 business has acknowledged “the reality of climate change”.