( CNN ) -- Tens of thousands of people marched through Manhattan sounding an urgent call for action to reverse global climate change Sunday . One marcher 's sign read `` cut your emissions or you 'll sleep with the fishes . '' The `` People 's Climate March '' in New York was billed as the largest of several protests held around the world two days before the start of the United Nations ' Climate Summit . U.N. Secretary General Ban Ki-moon walked with former U.S. Vice President Al Gore along the 2Â½-mile route . Celebrity protesters included comedian Chris Rock and actors Leonardo DiCaprio and Mark Ruffalo , who said he was marching for his children 's future . `` I see the world changing very quickly already , and I want to do my best to give them the best world that they deserve to have and that I was fortunate to come up into , '' Ruffalo told CNN . Opinion : Re : No one cares about climate change . Ricken Patel , the founding executive director of march organizer Avaaz , told CNN the `` solution is so clear . It 's to get to a 100 % clean energy power society and economy . '' `` We 're seeing massive droughts across the Midwest and California , '' Patel said . `` We 're seeing storms that are devastating the East Coast and the Gulf Coast . We 're seeing flooding that 's threatened this city and many others . All of those impacts that are happening , but it is just a taste test of what 's to come if we do n't urgently reverse course . '' The Environmental Defense Fund said it expected up to 100,000 people to walk , while the New York Police Department predicted about 30,000 would participate . Rallies were also held in London , Paris , Berlin , Tokyo and Bogota , Colombia . Opinion : Why climate change is an 'everybody issue ' now . World leaders converge on the U.N. headquarters in New York to offer and discuss climate change proposals starting Tuesday . Speakers will include President Obama and DiCaprio , who was recently appointed as U.N. Messenger for Peace with a focus on climate change . CNN 's Alison Kosik contributed to this report .
`` Cut your emissions or you 'll sleep with the fishes , '' marcher 's sign warns . `` People 's Climate March '' in New York is one of several around the world Sunday . Activist : Droughts , storms and floods are `` a taste test of what 's to come '' World leaders converge on the U.N. to discuss climate policy Tuesday .