NEW YORK- An international day of action on climate change brought tens of thousands onto the streets of New York City on Sunday, with organizers predicting the biggest protest on the issue in five years.

Some 100,000 people, including United Nations Secretary-General Ban Ki-moon, former U.S. Vice President Al Gore, actor Leonardo DiCaprio and elected officials from the United States and abroad joined the People’s Climate March, ahead of Tuesday’s United Nations hosted summit in the city to discuss reducing carbon emissions that threaten the environment.

Organizers said some 550 busloads of people had arrived for the rally, which followed similar events in 166 countries including Britain, France, Afghanistan and Bulgaria. Thousands more came by public transportation, walked or traveled in private cars. “Today I am marching for my children. I am marching so they can live in a world without worrying about the next big storm destroying their community,” said Bill Aristovolus, the superintendent of an apartment building in New York City’s working-class Bronx borough.

A crowd including U.S. senators Bernard Sanders of Vermont and Sheldon Whitehouse of Rhode Island marched along the city’s Central Park, through midtown Manhattan to Times Square, where they stopped for a moment of silence at 12:58 p.m. (1658 GMT).

Ki-Moon, wearing a blue T-shirt that read “I’m for climate action” marched arm-in-arm with primatologist Jane Goodall and French Ecology Minister Segolene Royal.

“This is the planet where our subsequent generations will live,” Ki-Moon told reporters. “There is no ‘Plan B,’ because we do not have ‘Planet B.’”

The drums, horns and chants that had echoed off skyscrapers halted and the bulk of the marchers stood still at 12:58 p.m. ET (1658 GMT) for a moment of silence.

Organizers billed the event as the largest gathering focused on climate change since 2009, when tens of thousands gathered in Copenhagen in a sometime raucous demonstration that resulted in the detention of 2,000 protesters. The march comes days after the U.S. National Oceanic and Atmospheric Administration reported that August 2014 was the warmest on record, some 1.35 degrees Fahrenheit (0.75 C) above the 20th century global average of 60.1 F (15.6 C).

New York City Mayor Bill de Blasio on Sunday unveiled a new plan for the city to reduce its greenhouse gas emissions by 80 percent from 2005 levels by 2050.

All 3,000 major city-owned buildings would be retrofitted with energy saving heating, cooling and light systems by then, he said.

, though meeting the commitment will also require significant investments by private landlords.

DiCaprio marched towards the front of the group, with members of an Ecuadorean tribe who have fought a years-long legal battle with Chevron Corp over Amazon pollution.

“This is the most important issue of our time,” DiCaprio said. “I’m incredibly proud to be here.”