WASHINGTON — Greta Thunberg, the famous 16-year-old Swedish environmental activist who kicked off a global movement of students leaving school to demand action on the climate crisis, joined other youth activists at a rally outside the White House on Friday. A few hundred people, mostly teenagers and young children, gathered on the Ellipse south of the White House carrying signs that read “I want you to panic!” and “Why are we studying for a future we won’t have?” They chanted, “This is a crisis, act like it!” and “No more coal, no more oil, keep that carbon in the soil.” When someone mentioned President Donald Trump, the crowd booed and yelled “Shame!”

NICHOLAS KAMM via Getty Images Swedish environmental activist Greta Thunberg, 16, takes part in a climate protest outside the White House in Washington, D.C., on Friday.

After marching a short distance toward the White House, numerous protesters lay down on the ground for an 11-minute “die-in” ― what one speaker called a “mass extinction.” The protest represented the 11 years that scientists say world governments have to rein in greenhouse gas emissions to stave off potentially cataclysmic climate change. “We are striking today to save tomorrow!” Nadia Nazar, the 17-year-old co-founder of the Zero Hour movement. Trump has a long history of denying the threat of climate change, often arguing that spells of cold weather somehow disprove the long-term warming trend. His administration has taken an ax to a slew of environmental regulations meant to curb greenhouse gas emissions ― all part of its so-called “energy dominance” agenda. Thunberg told CBS in an interview last month that she wouldn’t “waste time” talking to Trump if given the opportunity. Thunberg spent most of the rally surrounded by peers and a throng of reporters wielding cameras. She quietly joined a series of chants, and when finally given a chance to speak, simply expressed her gratitude for such a large turnout. “This is very overwhelming,” she said. “Never give up. We will continue.”

NICHOLAS KAMM via Getty Images Greta Thunberg speaks at a climate protest outside the White House.