The United Nations Secretary General has called for world leaders to make “bold pledges”, and sign up to a new global agreement on climate change next year.

Speaking as the UN climate change summit opened in New York, Ban Ki-moon said carbon emissions had to be reduced to limit global temperature rises to under two degrees Celsius.

He cited public pressure seen at large worldwide demonstrations at the weekend.

“In cities around the world hundreds of thousands of people called for action. They demanded that leaders lead. That is why we are here today. We are not here to talk, we are here to make history, today. Thank you for your leadership, thank you,” he said.

Ban Ki-moon called for 100 billion dollars a year from governments for a global fund.

France has joined Germany in pledging a billion dollars.

Hollywood actor Leonardo DiCaprio, now a UN representative on climate change, called for more investment in renewable energy.

“We need to put a price tag on carbon emissions, and eliminate government subsidies for all oil, coal and gas companies. We need to end the free ride that industrial polluters have been given in the name of a free market economy. They do not deserve our tax dollars, they deserve our scrutiny, for the economy itself will die if our ecosystems collapse,” DiCaprio told the session.

This is the first top-level world gathering on climate change since the Copenhagen summit in 2009, which was widely seen to have failed.

Among the most highly anticipated speakers at the summit on Tuesday was US President Barack Obama.

On Monday night about 1,000 activists blocked parts of New York’s Broadway. It followed Sunday’s demonstration in which about 100,000 people marched in the city.

The organisers of #FloodWallStreet said the protest aimed to disrupt business in the financial district by targeting what they called “corporate polluters and those profiting from the fossil fuel industry.”

More than 100 people – including a person dressed as a polar bear – were arrested, mostly for disorderly conduct.