Over one million young people marched in cities across the globe on Friday in what organizers expected to be the largest #schoolstrikeforclimate actions yet.

With chants including "Save our planet, save our future," and placards with messages such as "Act like the house is on fire," the youth-led actions represented a unified call for urgent and sweeping measures to address the climate crisis.

Organizers said over 1.8 million people took part in over 2,000 actions in 125 countries—a participant figure that, if confirmed, would surpass the massive turnout for the previous coordinated global strikes in March.

Claudia Sachs kicked off the student climate strike in front of the White House with her original song, “Future of Humanity.” I am SO inspired by these teenage activists calling for a Green New Deal. Now on to a march to the Capitol. pic.twitter.com/yWOPa2f7Dy — Noah Sachs (@nsachs1) May 24, 2019

Images of the actions—from London to New Delhi to Cape Town—were widely shared on social media.

Amanda Rodrigues, a junior who co-organized the day's action at Farmington High School in Connecticut, explained her motivation for the mobilization.

"The world is our home, right?" Rodrigues told the Hartford Courant. "So we have to do the best we can to preserve it. If the adults in our politics aren't making a change, then we have to take a stand."

Doing so, said Swedish teen Greta Thunberg, whose picketing outside the Swedish parliament catalyzed the weekly climate strikes, indeed has an impact.

"Activism works," she tweeted ahead of the marches. "So act. Join us!"