With US President Donald Trump and other sceptics calling climate change a hoax, the UN's climate science body must tell the world in a "very clear way" that humans are heating the planet, its chairman told AFP.

Jim Skea, a Scottish professor, chairs the Intergovernmental Panel on Climate Change (IPCC), which held a five-day meeting in a skyscraper outside Paris this week to begin drafting the next major UN climate assessment.

The gathering of more than 600 scientists from around the world, which ends Friday, kicked off a process that will culminate in the publication of the massive report by 2028 or 2029.

Established in 1988, the IPCC assesses global climate research and issues comprehensive reports every five to seven years to inform policymakers and guide climate negotiations.

QUESTION: You said recently it is "almost inevitable" the world will cross the 1.5C warming threshold. If this happens before the next IPCC assessment is published, what should it emphasise to remain relevant and impactful?

ANSWER: "The messages are that if we want to return global warming to 1.5C, it's quite clear what steps need........

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