As world leaders begin arriving for a summit at the United Nations on accelerating action to address climate threats, adults are planning to join students in an unprecedented wave of youth-led climate protests on Friday, organizers said. More than 1,000 strikes are planned across the United States and some 5,200 globally in more than 150 countries, said Alexandria Villaseñor, co-founder of the US Youth Climate Strike movement, and May Boeve, head of climate group 350.org. The protests will mark the first time adults are joining student strikes on a significant scale, likely giving them added numbers, publicity and impact, organizers said. “Expect tomorrow to be the largest global mobilization in climate action that has ever been seen in history,” Villaseñor said. Swedish teen activist Greta Thunberg will lead the protest in New York City, which is allowing children to miss school, joined by labor union activists and others, Villaseñor said. “We need everyone,” Villaseñor said. “Make your voices heard.”Protesters are demanding an immediate end to expansion of fossil fuel infrastructure and that major producers of climate-changing emissions be held accountable for damages, he said. They also want stronger efforts to spur transitions to renewable energy with opportunities for workers who may lose their jobs in fossil fuel businesses, Villaseñor said.