Tens of thousands of people marched through London today to demand urgent action on climate change, as events took place around the world ahead of a UN climate summit.
Celebrities including actress Emma Thompson, musician Peter Gabriel and designer and activist Vivienne Westwood joined an estimated 40,000 people to march through Westminster calling on politicians to tackle global warming.
The march and rally was one of 2,000 events taking place in 150 countries around the world ahead of a UN climate summit next week, which more than 120 leaders including David Cameron and US president Barack Obama are expected to attend.
Upwards of 100,000 people are expected to take to the streets of New York, where the summit is being held, for the People's Climate March.
The UN summit has been convened by Secretary General Ban Ki-moon in a bid to drive action and momentum towards talks in Paris in 2015, where it is hoped a new global climate treaty can be agreed.
In London campaigners carrying banners that said "renewables rock", and "for the love of polar bears and rhinos" marched through the streets, chanting "What do we want? Clean energy. When do we want it? Now."
Puppet giraffes, birds and zebras were joined by protesters dressed as pandas and parents with their children in push-chairs.
Nathan Williams, a TV director from Kilburn, north west London, carried his six-year-old daughter, who was dressed as the princess from the film Frozen and held a banner which said: "keep things frozen".
He said of climate change: "It's such a big issue for our lives, and even more for her life."
Speaking at the start of the march, Thompson said: "This is important for every single person on the planet, which is why it has to be the greatest grass roots movement of all time."
She said that fossil fuels had been a good idea at the time - like tobacco - but now it was clear they were killing people.
"Climate change has been a bit like everybody playing a deadly game of grandmother's footsteps for the last 20 years, now this climate change grandmother has turned around and started running towards us.
"It's touch and go whether we're going to survive what we've done."
Thompson has just returned from a trip to the Arctic where, she said, "the effects of the melting ice are written so clearly on the landscape".
She added that everyone has to act on cutting emissions.
But she said: "An international climate deal is of absolutely vital importance. It must be put into law. It can't be a non-binding agreement. Those agreements have fallen to pulp in our hands over the last 20 years."
She criticised David Cameron for encouraging oil, gas and coal, and said the politics of fighting climate change were "profound, and deep and dirty".
She added: "This is the battle of our lives. We're fighting for our children."
Greenpeace UK executive director John Sauven, who was also on the march, said scientists were clear about the dangers of climate change, and most world leaders understood the science, but were failing to respond to what needed to happen.
He said events were taking place today from Papua New Guinea and Australia to the march in New York.
"That is really what we need - global pressure coming from below on our political leaders."
He said Mr Cameron was going to the climate summit at a time when the UK was burning "unbelievable" amounts of coal, and called on the Prime Minister to announce a phase-out of coal power in the UK.
Leo Hickman, chief climate change adviser for conservation charity WWF-UK, said that while the risks of climate change had been well known for a decade or more, the opportunities associated with tackling the problem were emerging.
Recent research has shown that innovative technology and new investment in cities, energy and agriculture could cut emissions at the same time as saving money, boosting growth and improving health.
"We shouldn't be scared of decarbonising, it isn't going to wreck our economy. For the UK economy there's some really clear opportunities and co-benefits of decarbonising. We should grasp this moment rather than be scared of it," he said.
Campaign groups including Avaaz, Greenpeace UK, Christian Aid and Friends of the Earth took part in the march in London, while other events were taking place in cities around the UK.
Friends of the Earth's policy and campaigns director Craig Bennett said: "This is a global call for action that mustn't be ignored.
"It's time to end our dangerous addiction to dirty fossil fuels and plug into a clean energy system fuelled by the wind, waves and sun - with wealthy developed nations like the UK taking the lead.
"Half measures and empty promises are not enough. Our leaders must take urgent action to prevent the world speeding towards catastrophic climate change."
Christian Aid's senior climate change adviser, Mohamed Adow, who is taking part in the New York march, said: "People around the world have demonstrated just how much this issue means to them by coming out onto the streets of their cities in the biggest ever mobilisation for the climate.
He added: "There is still time for us to change our course and put the world on a trajectory which will secure a safe and healthy future for us all.
"But we need to see political commitments this year. We cannot leave it until next year's crunch meeting in Paris in December.
"The People's Climate March shows that the time for action is now. This week world leaders have a chance to prove they can be trusted to do the right thing."