World Wildlife Fund is asking everyone to switch off their lights for an hour at 8.30pm this Saturday to show their support for global action on climate change.

WWF wants a billion people around the world to take part – making this the biggest campaign in history.

And of all the cities in the world to spearhead the campaign, it has chosen Bristol because of its eco-friendly credentials.

Bristol city council has signed up to WWF's Earth Hour as well as tourist attractions such as the SS Great Britain.

Organisers are hoping that even the lights on the Bristol suspension bridge will switch off at 8.30pm and Bristol Zoo will have a torchlit event.

Some 1180 cities from 80 countries across the globe have signed up, including Nelson's Column, The London Eye and Sydney Opera House.

WWF says time is running out to implement an effective global response to the threat of climate change.