People gather near Columbus Circle before the People's Climate March in New York Sunday, Sept. 21, 2014.

People protest for greater action against climate change during the People's Climate March, in New York City, Sept. 21, 2014.

Activists lead with a float while taking part in the People's Climate March in New York City, Sept. 21, 2014.

Demonstrators make their way down Sixth Avenue in New York during the People's Climate March, Sept. 21, 2014.

From left, designer Vivienne Westwood, musician Peter Gabriel and actress Emma Thompson join an estimated 40,000 thousand people marching from the Embankment via Whitehall to the Houses of Parliament in London, Sept. 21, 2014, as part of the People's Climate March, a worldwide mobilization calling on world leaders to commit to urgent action on climate change and 100% clean energy.

Leonardo DiCaprio attends The People's Climate March on Sept. 21, 2014 in New York City.

Actress Emma Thompson with a placard made by her daughter Gaia joins an estimated 40,000 thousand people marching from the Embankment via Whitehall to the Houses of Parliament in London, Sept. 21, 2014 as part of the People's Climate March.

Sting attends The People's Climate March on Sept. 21, 2014 in New York City.

Actor Mark Ruffalo participates in the People's Climate March on Sept. 21, 2014 in New York City.

A woman with a green heart painted on her face holds a flag during the People's Climate March at Ipanema beach, Rio de Janeiro, Brazil, Sept. 21, 2014.

Demonstrators make their way down Sixth Avenue in New York City during the People's Climate March, Sept. 21, 2014.

People protest for greater action against climate change during the People's Climate March on Sept. 21, 2014 in New York City.

Demonstrators in animal costumes walk in the "People's Climate March" in central London, Sept. 21, 2014.