People organize to march in the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
People practice yoga before marching in the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
People organize to march in the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
Actor Leonardo DiCaprio walks down 6th Avenue during the the People's Climate March on September 21, 2014 in New York. Activists mobilized in cities across the globe Sunday for marches against climate change, with one of the biggest planned for New York, where celebrities, political leaders and tens of thousands of people were expected. The march comes before the United Nations Secretary-General Ban Ki-moon convenes a climate change summit of 120 world leaders . AFP PHOTO/Timothy A. Clary (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images)
People's Climate March
People march down Sixth Avenue during the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
People protest for greater action against climate change during the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
People protest for greater action against climate change during the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
People protest for greater action against climate change during the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
People protest for greater action against climate change during the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
People protest for greater action against climate change during the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
People march down Sixth Avenue during the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
People protest for greater action against climate change during the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
A demonstrator poses during the People's Climate March on September 21, 2014, in New York. Activists mobilized in cities across the globe Sunday for marches against climate change, with one of the biggest planned for New York, where celebrities, political leaders and tens of thousands of people were expected. The march comes before the United Nations Secretary-General Ban Ki-moon convenes a climate change summit of 120 world leaders . AFP PHOTO/Timothy A. Clary (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images)
People's Climate March
A demonstrator takes part in the People's Climate March on September 21, 2014, in New York. Activists mobilized in cities across the globe Sunday for marches against climate change, with one of the biggest planned for New York, where celebrities, political leaders and tens of thousands of people were expected. The march comes before the United Nations Secretary-General Ban Ki-moon convenes a climate change summit of 120 world leaders . AFP PHOTO/Timothy A. Clary (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images)
People's Climate March
A demonstrator takes part in the People's Climate March on September 21, 2014, in New York. Activists mobilized in cities across the globe Sunday for marches against climate change, with one of the biggest planned for New York, where celebrities, political leaders and tens of thousands of people were expected. The march comes before the United Nations Secretary-General Ban Ki-moon convenes a climate change summit of 120 world leaders . AFP PHOTO/Timothy A. Clary (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images)
People's Climate March
United Nations Secretary General Ban Ki-Moon participates in the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
Primatologist Jane Goodall, Former U.S. Vice President and environmental activist Al Gore, New York City Mayor Bill deBlasio and United Nations Secretary General Ban Ki-Moon participates in the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
Primatologist Jane Goodall, Former U.S. Vice President and environmental activist Al Gore, New York City Mayor Bill de Blasio and United Nations Secretary General Ban Ki-Moon participates in the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
Primatologist Jane Goodall participates in the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)
People's Climate March
Actor Mark Ruffalo participates in the People's Climate March on September 21, 2014 in New York City. The march, which calls for drastic political and economic changes to slow global warming, has been organized by a coalition of unions, activists, politicians and scientists. (Photo by Andrew Burton/Getty Images)