"Please save your praise. We don't want it."

That was the blunt message 16-year-old Swedish climate activist Greta Thunberg delivered directly to U.S. lawmakers Tuesday during a meeting of the Senate Climate Change Task Force, which featured testimony from young environmentalists demanding that members of Congress treat the ecological crisis with the urgency it deserves.

"Don't invite us here to just tell us how inspiring we are without actually doing anything about it because it doesn't lead to anything," said Thunberg. "If you want advice for what you should do, invite scientists, ask scientists for their expertise. We don't want to be heard. We want the science to be heard."

After Sen. Tom Carper (D-Del.) told the young activists that they will soon have an opportunity to run for political office, Thunberg said: "We don't want to become politicians, we don't want to run for office. We want you to unite behind the science."

"I'm sorry," Thunberg added, "I know you're probably trying very hard, and this is not personally to any one of you but generally to everyone. I know you're trying, but just not hard enough."

In a tweet following the meeting, Sen. Ed Markey (D-Mass.)—the lead sponsor of the Senate Green New Deal resolution—said that "by failing to take meaningful action on climate, our leaders failed the young people of the world."

"A generation of leaders owes our youngest generations an apology," said Markey, "and a commitment to finally take the bold action we've failed to achieve."

The task force meeting came just days before millions of people are expected to take to the streets for the youth-led global climate strikes on Friday. According to 350.org, there are more than 4,400 strikes registered across the globe and over 800 strikes planned in the U.S. alone.

Wednesday night, Thunberg—whose activism helped inspire the global strike—is set to deliver a major address to members of Congress on Capitol Hill.

"She's not known to mince words," said Jamie Henn, strategic communications director with 350.