DES MOINES — During Saturday night’s Democratic debate here, Bernie Sanders stuck to his assessment that climate change is the biggest national security threat facing the United States.

The senator from Vermont made the same assertion in the first debate, and he was pressed by CBS News’s John Dickerson, the debate moderator on Saturday, on whether his view had changed in light of the terrorist attacks in Paris a day earlier. Sanders said it had not.

On Sunday, Dickerson followed up with Sanders as the senator made an appearance on CBS's “Face the Nation,” which Dickerson hosts. Sanders said the CIA and the Defense Department back up the notion that climate change can lead to terrorism, and aides later pointed to a report bolstering his case.

“If we are going to see an increase in drought, flood and extreme weather disturbances as a result of climate change, what that means is that people all over the world are going to be fighting over limited natural resources,” Sanders said. “If there is not enough water, if there is not enough land to grow your crops, then you’re going to see migrations of people fighting over land that will sustain them, and that will lead to international conflicts.”

“But how does drought connect with attacks by [the Islamic State] in the middle of Paris?” Dickerson asked.

“When you have drought, when people can’t grow their crops, they’re going to migrate into cities, and when people migrate into cities and they don’t have jobs, there’s going to be a lot more instability, a lot more unemployment and people will be subject to the types of propaganda that al-Qaeda and ISIS are using right now,” Sanders said, using an alternative name for the Islamic State. “So where you have discontent, where you have instability, that’s where problems arise, and certainly, without a doubt, climate change will lead to that.”

When another Democratic contender, former Maryland governor Martin O’Malley, made a similar argument this summer, Republicans ridiculed him.

In a statement at the time, Republican National Committee Chairman Reince Priebus branded O’Malley’s position “absurd,” adding that “it’s abundantly clear no one in the Democrat Party has the foreign policy vision to keep America safe.”

An aide to O’Malley said the Republicans were denying science.

Sanders, who is competing with Hillary Rodham Clinton for the Democratic nomination, could be in for some of the same criticism.

Later Sunday on "Face the Nation," panelist Peggy Noonan, a Wall Street Journal columnist and former speechwriter for President Ronald Reagan, said Sanders's comments made him look "slightly daffy."