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
