What is climate change?

The UK, France and the UN are hosting a virtual climate meeting on Saturday. About 75 world leaders will attend, marking five years since the adoption of the Paris climate agreement. Pope Francis will also address the meeting.

This virtual gathering is taking place after the pandemic caused the postponement of the annual Conference of the Parties, due to take place in Glasgow this year.

Nations will be revealing how they intend to cut their greenhouse gas emissions which means we’ll find out if their commitments are ambitious enough to stop the worst effects of climate change. But just what is climate change? And why are scientists calling for urgent action?

The BBC's global science correspondent Rebecca Morelle explains.

Produced and edited by Larissa Kennelly

Graphics by Terry Saunders

This video was first published in January 2020.