SCOTT SIMON, HOST:
Thousands of environmental activists from around the world are expected to march in New York City tomorrow. Organizers of the People's Climate March say it will be the largest climate change demonstration in history. They're trying to send a message to world leaders gathering for the United Nation's Climate Summit next week. NPR's Joel Rose reports.
JOEL ROSE, BYLINE: The biggest previous climate change protest was five years ago in Copenhagen, where an estimated 100,000 people showed up. The organizers of the People's Climate March hope to crush that record.
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MARILYN VASTA: Hi. Join us for the march on Sunday. Great, great, hope you can make the march.
ROSE: Marilyn Vasta is handing out fliers in midtown Manhattan. She's part of the host committee that spent five months organizing tomorrow's march, along with more than 1,400 schools, faith groups and other organizations.
VASTA: I think if we have a massive turnout, it will really say to world leaders, people get this. You can't be a world leader if you are doing nothing about the biggest crisis this civilization has ever faced. You're not leading.
ROSE: Those leaders are gathering for a U.N. Climate Summit next week, at the invitation of Secretary-General Ban Ki-moon. The goal is to work toward international agreements that would lower greenhouse gas emissions. So far, that's been a tough sell with many governments, including the U.S.
BILL MCKIBBEN: We won the argument 20 years ago. Science is not in doubt. We've just lost the fight.
ROSE: Bill McKibben is a writer, professor and activist, who led the call for the massive march in New York. There will be no speeches, no stage, no celebrity headliners. McKibben says the size of the march is the message, and that protesters are encouraged to bring trumpets, whistles and anything else that makes noise.
MCKIBBEN: We're going to sound the climate alarm. We're going to sound the smoke alarm for a planet on fire. We're going to make a hell of a lot of noise. The time has come for these guys to stop talking and offering fine speeches and start actually doing something.
MOISES NAIM: What matters as much as how many people show up in the March, is what happens the day after.
ROSE: Moises Naim is with the Carnegie Endowment for International Peace. And he says most street protests don't work. He points to Occupy Wall Street as an example of a protest that had no specific demands, and therefore little concrete impact. Naim is concerned that the agenda of this Climate March is similarly vague.
NAIM: Because they are not connected with a political machine. There is a lot of energy in that street; a lot of people with a lot of passion. But in fact, they are not targeting anyone concretely because when you target everyone, you're not targeting anyone specific.
ROSE: But the Climate March's organizers say it's already built connections that will help them ahead of next year's big climate conference in Paris. And they say they're inspired by past protests that did leave a mark on history, like the Civil Rights March on Washington in 1963. That's what motivates demonstrator Kim Morrow. She and her daughter rode the train to New York this week from Nebraska.
KIM MORROW: People turn out in the streets when the issue boils over to that level of just absolutely demanding change to happen. And now we're seeing that climate change is the most pressing moral issue of our time.
ROSE: Organizers say they're expecting more than 400 buses full of protesters from around the country. Even U.N. Secretary-General Ban Ki-moon will walk with the demonstrators. They hope the sound of the march will still be ringing in the ears of world leaders when the Climate Summit opens on Tuesday. Joel Rose, NPR News, New York. Transcript provided by NPR, Copyright NPR.