A Donald Trump triumph in the US presidential election would be a "disaster" for the environment, a climate scientist has warned.
Joanna Haigh, professor of atmospheric physics at Imperial College London, said it is "terribly worrying" to think about what the consequences would be if Mr Trump were to become president.
Her comments come just days ahead of the world's first comprehensive climate treaty coming into force.
The Paris Agreement commits countries to cutting greenhouse gas emissions to net zero to stop dangerous climate change.
Prof Haigh told the Press Association: "Donald Trump actually refutes climate change as a human-induced temperature increase and has said he will withdraw from any internationally-agreed climate change, so if the US then says it's not going to participate, I can't imagine what will happen, because how will other countries, especially those that have more difficulty, developing countries, how will they manage to do it without the US? It's just terribly worrying."
Speaking on whether it would be detrimental if Mr Trump were to attend key environment-related meetings or conferences as president, Prof Haigh said: "If it's him, or his administrators that go along with whatever he says, then yes it would be a disaster."
She said it would be a disaster "for the world", adding: "That's not overstating it."
Asked if she thinks he could be convinced to change his views on the issue, Prof Haigh said: "I doubt it. I think from what I've seen he's only got one thing that he cares about, which is his own career and his own persona and how he's perceived."
Prof Haigh said she would hope UK leaders would not allow themselves to be influenced by Mr Trump if he was to become president.
"Let's hope they'd have a bit more oomph to them, a bit more backbone. But of course they will have to go to meetings and talk to him.
"They'll have to enter negotiations with him. I don't know. I'd hope it wouldn't water down their commitment and certainly the information that the British Government will be getting from us and from other people around - 'We still need to carry on and do this if we don't want a much warmer world'."
Prof Haigh was speaking after a briefing on the state of the climate at the Science Media Centre in London.