UN chief on streets for climate deal
UN Secretary General Ban Ki-moon and actor Leonardo di Caprio will join thousands in a march for climate action in New York on Sunday.
The Manhattan demonstration is part of a global protest, with over 2,000 marches taking place around the world.
Mr Ban will also tackle the issue with 125 heads of state and government on Tuesday at UN headquarters.
It will be the first such gathering since the unsuccessful Copenhagen conference in 2009.
The meeting will attempt to push forward political momentum towards a new universal agreement on climate to be signed by all nations at the end of 2015.
To maintain pressure on the political leaders, the People's Climate March has been carefully organised to show that there is popular support for action to curb carbon emissions.
Speaking before the event Mr Ban said he wanted to take part to show he supported the need for rapid action.
"I will link arms with those marching for climate action," he told a news conference.
"We stand with them on the right side of this key issue for our common future."
Joining him will be the Wolf of Wall Street star, who has recently been appointed a UN Messenger of Peace with special responsibility for climate change.
Mr Di Caprio tweeted at the time that he was "honoured to accept at this key moment".
In New York, the march will also be attended by former Vice President Al Gore and French Foreign Minister Laurent Fabius.
It will feature thousands of colourful displays of art, all designed to enhance an intended narrative that the time for dithering is over.
"I think at this point everyone around the world is feeling the urgency and our institutions are behind the curve," said Gal Golan, one of the artists working on the march.
"This moment becomes crucial for asserting that action is necessary immediately, and we have very limited time to make changes to avoid unprecedented levels of catastrophe."
Explaining why the UN secretary general was taking part, Mary Robinson, former UN special envoy, explained: "I think the Secretary General recognises that this is for everyone, and it is important that in every country civil society comes out and puts pressure on their leaders to make the changes necessary so that we will have a safe world.
"He doesn't see the marchers as them and the insiders as being an us, rather he sees the two as part of building a momentum, it is civil society asking their leaders to be more ambitious."
The artists are being joined by a diverse range of people including scientists, religious leaders, and farmers. Also in attendance will be survivors of Tropical Storm Sandy and Hurricane Katrina, as well as indigenous tribes from South America and elsewhere.
Organisers have spent six months preparing the protests in places as diverse as Papua New Guinea, Lagos, London and Rio where the famous statue of Christ will be turned green.
They believe that a huge global turnout can't be ignored by the heads of state and government that will convene at UN headquarters on Tuesday.
"The march is incredibly important, because it will help draw policy makers and corporate leaders' attention to the importance of climate change, including the need to adapt to climate change," said Dr Jessica Hellmann, associate professor of biological sciences at the University of Notre Dame.
"The march demands that government grow its commitment to adaptation. The diversity of people participating in the climate change march all around the world, sends a strong message that everyone is affected by climate change."
Mr Ban has asked that the political leaders come to UN headquarters bearing pledges of action. He wants to hear commitments to cut carbon and offers of finance for those most affected.
It remains to be seen how significant these will be.
The leaders of China, India, Australia, Russia and Canada won't be here. Observers believe the meeting can still achieve political momentum. After all, there will be more leaders in New York than in Copenhagen in 2009 when hopes of a last minute deal were dashed in confused and rancorous discussions.
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