Former Texas Congressman Beto O'Rourke said on Thursday that he has not "seen anything better" than the Green New Deal proposed by Rep. Alexandria Ocasio Cortez, D-N.Y., to deal with climate change, an issue that he said could "at its worst, lead to extinction."

Speaking in a coffee shop in Keokuk, Iowa, on his first day as a candidate for president, the 46-year-old Democrat applauded supporters of the Green New Deal for tying environmental justice to the creation of new jobs and the rectification of racial inequities.

"So, some will criticize the Green New Deal for being too bold, or being unmanageable," O'Rourke said. "But, I'll tell you what. I haven't seen anything better that addresses this singular crisis that we face, a crisis that could, at its worst, lead to extinction."

O'Rourke painted a dour picture of the future, but urged those around him to "find a way to do this," noting that "literally the future of the world depends on us, right now."

He said that his 12-year-old son, Ulysses, "who in 2050 is going to be just about my age, is going to be looking back on this moment in 2019 in Keokuk and every moment thereafter to judge what we did or what we failed to do. Because his kids — his kids' life, whether they can even breathe, is dependent on what we do right now."

He said that to reduce dependence on fossil fuels "not only must we emit less greenhouse gasses — we must also plant those things that absorb greenhouse gasses and carbon, and we must also invest in the technology that will allow us to claim some of it that is in the air right now."

"Can we make it? I don't know," he said. "It's up to every single one of us."

The sweeping resolution, introduced by Ocasio-Cortez in the House of Representatives and Sen. Edward Markey, D-Mass., is not binding, but its proposals, if implemented, would be costly.

A report produced by the American Action Forum, a right-leaning think tank, pegged its total cost at between $51 trillion and $93 trillion, though most of that cost comes from planks of the proposal that are not directly related to climate, including roughly $36 trillion included for universal health care.

Even given the Green New Deal's ambitious goals, O'Rourke said it would not be enough to fully deal with the problem that climate change poses. But he said that "this is our final chance."

"Let us all be well aware that life is going to be a lot tougher for the generations that follow us no matter what we do. It is only a matter of degrees," O'Rourke said.

Republicans have mocked the Green New Deal for its hefty price tag, and even senior Democrats have balked at the proposal. Sen. Dianne Feinstein, D-Calif., made headlines last month after a video went viral of her telling young supporters in her San Francisco office that "there's no way to pay for it."

Its cosponsors in the senate include a number of presidential candidates, including Sen. Kirsten Gillibrand, D-N.Y., Sen. Bernie Sanders, I-Vt., Sen. Kamala Harris, D-Calif., Sen. Elizabeth Warren, D-Mass., Sen. Cory Booker, D-N.J., and Sen. Amy Klobuchar, D-Minn.

Scientists have warned that rapid, unprecedented change is necessary to prevent the worst effects of climate change, including extreme weather and loss of species.

Despite O'Rourke's strong talk on Thursday, he has been criticized by progressives for taking contributions from oil and gas executives despite signing a pledge to reject them during his failed bid for senate. In December, the investigative news outlet Sludge reported that he had been removed from the "No Fossil Fuel Money Pledge."