The United States presidential election will be "make or break" for the planet after four years during which Donald Trump frustrated global efforts to slash emissions, climate experts warn, fearing his re-election may imperil the world's chances of avoiding catastrophic warming.
In a year dominated by the coronavirus pandemic, increasing signs of the brutal impacts of climate change have come into view, with record temperatures, sea ice loss and enormous wildfires scorching parts of the Arctic Circle, Amazon basin and the US itself.
Scientists say the window of opportunity to contain Earth's warming is narrowing fast. This deadline magnifies the global significance of American voters' choice between Trump and his Democratic challenger Joe Biden to lead the world's second-largest emitter for the next four years.
Trump, who has described climate change as a hoax, has doubled down on support for polluting fossil fuels and revoked or rolled back a host of environmental standards.
On Thursday's last presidential debate, Trump charged that Biden's climate plan was an "economic disaster" for oil states such as Texas and Oklahoma. Biden said that climate change is "an existential threat to humanity. We have a moral obligation to deal with it."
And just a day after the US vote on November 3, the country will formally withdraw from the Paris agreement, the international accord aimed at restraining emissions and averting runaway warming.
Trump's signature act of climate disruption has "already diminished our moral standing, taking us from a leader to the rear of the pack", climate scientist Michael Mann told AFP.
Without US climate leadership "I fear that the rest of the world will not take seriously enough their obligations to reduce emissions in time to avert the worst impacts of climate change," he said. "That's why I've called this a make-or-break election when it comes to the climate."
US withdrawal has not dampened others resolve, at least for now. The European Commission now wants emissions in Europe cut 55 percent by 2030. But it was China's recent vow to go carbon neutral by 2060 that has the potential to be a "game-changer", according to Lois Young, Belize's envoy to the UN, although she noted the plans unveiled by the world's largest emitter were still light on detail.
But the US is still crucial.
Laurence Tubiana, who was a key architect of the Paris deal as France's top negotiator, said the rest of the world simply "cannot compensate" for the country's emissions. While US states and businesses have independently acted to cut carbon, Tubiana predicted their efforts would fall short without new government policy.
In this context, she said a second Trump term would be "very bad news".