What is COP and why does it matter?

With the leaders of some of the world's most polluting countries - the US, China and India - set to skip it, is the COP climate conference irrelevant?

The event in Brazil next week marks three decades of target-setting and financial pledges - yet temperatures are still rising and so are emissions.

Were all those promises a load of hot air? Have dreams of net zero gone up in smoke?

Niall is joined by our science and technology editor Tom Clarke who is at the summit.

Producer: Araminta Parker

Editor: Mike Bovill