Former Vice President Al Gore spoke about climate change Wednesday night at Tufts University, and challenged students there to do something about the crisis.

Gore shared some scary news about our climate, including that we’re in danger of losing half of all living species on the planet in this century. He spoke about the extreme weather events that have become commonplace around the globe. “Mother Nature has now joined the debate and is more persuasive than any of us could be,” he said.

He told students the technologies needed to solve the climate crisis currently exist.

“What we still lack is sufficient political will to implement them quickly enough to forestall the worst consequences of this crisis,” he said. “I’m an optimist. But my optimism is premised on the assumption that this awakening that we now see beginning will burgeon and will grow, and that we will find the political will.”

Gore asked the students to step up and become active on the issue. “I’m not here just to inform or entertain you,” he said to the packed auditorium. “I’m here to recruit you. I’m serious. This is the challenge of our time.”

Gore said fossil fuels still provide 80 percent of the world’s energy, putting 110 million tons of climate-changing greenhouse gases into the atmosphere every day. But he said our “official attitude” has been to not care about it.

“Well, we should care,” he said. “And the way we can embody that caring is by saying you have to pay a price if you're going to use the sky as an open sewer and the price ought to be high enough to discourage you from doing it and to steadily reduce the amount.”

A national price on carbon is unlikely under the Trump administration. But in Massachusetts, the Legislature’s omnibus energy bill coming out next week is expected to require Gov. Charlie Baker’s administration to choose a carbon pricing scheme for transportation and for buildings in the next four years. Carbon emissions from the state’s energy generation are handled through the Regional Greenhouse Gas Initiative (RGGI), a multi-state cap and trade system.

Gore pushed back on a student’s question that suggested there needs to be a choice between reduced emissions and economic growth. “You have achieved, in this Commonwealth, a significant reduction in greenhouse gas emissions and a significant increase in economic growth,” Gore said.

“We know the problem is real. We know how to solve it. And for those who think we don't have enough political will, just remember, political will is itself a renewable resource,” he told the students. “Help renew it.”