Major disruption is expected in central London this weekend as environment activists engage in a day of action dubbed "Rebellion Day".
Organisers from the Extinction Rebellion movement told Sky News that more than 1,000 protesters are planning to block Blackfriars, Waterloo, Westminster, Lambeth and Southwark bridges as part of the event.
The protest is to draw attention to the group's campaign for immediate and dramatic action on climate change by the UK government.
"A little incremental change will do nothing," Miles Glyn, an activist involved in organising Saturday's protest told Sky News. "It's only a massive change that may mitigate what is happening and maybe make a better future."
The group claims scientific data, that shows the enormity of climate change, has been ignored by governments across the world and that ecological catastrophe, and subsequent social collapse, is possible within a generation.
"I hear more and more information and I feel like I can't ignore it anymore," one Extinction Rebellion volunteer told Sky News. "It's undeniable what is happening and a lot of people in authority know all of this."
A leading climate change scientist told Sky News that although the UK has ambitious climate change targets, it has yet to implement them fully.
Swenja Surminski, head of adaptation research at London School of Economics, said: "On paper, the UK is actually a world leader in terms of technology, and also in terms of ambitions. We have a climate change act, which sets out what we need to do, but unfortunately the policies are lagging behind.
"If we wait, the cost, in terms of the catastrophes, in terms of impact on our economic system and things like water shortages which was have already seen, the longer we wait, the costs will just get higher."
Extinction Rebellion uses mass acts of civil disobedience to draw attention to its concerns and to galvanise change.
The group compares itself to the suffragette and US civil rights movements and says many of its volunteers are prepared to be arrested, or go to jail, for their convictions.Among its demands are:
Actions over the past week have included spray-painting the walls surrounding the Houses of Parliament and protesters gluing their hands to the entrance to the Department of Energy in central London.
But Saturday's Rebellion Day is set to the be the biggest yet.
Organiser Dr Gail Bradbrook said: "What's really happening is that [our volunteers] say 'I've tried everything else, I've been on marches, I've signed petitions, I've donated money, I've been to my MP.' What's left to do but to break the law? Because within that spirit you are saying enough is enough."