The spectre of humanity's failure to curb heat-trapping emissions hangs over climate negotiations in Brazil, after the UN confirmed the planet is now certain to "overshoot" 1.5C of warming and faces a tough battle to bring temperatures back down.

Global tensions, economic uncertainty and a US administration under Donald Trump that is hostile to climate science have snatched political focus away from tackling the fossil fuel pollution and environmental destruction driving warming.

With tepid climate ambition and emissions still rising, UN Secretary-General Antonio Guterres recently acknowledged that crossing 1.5C in the coming years was now inevitable.

But he insisted the world must not give up on the Paris Agreement's safer goal.

"The path to a livable future gets steeper by the day. B

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