Chuck Hagel: “Climate change is a significant concern for DOD, affecting the operating environment as well the roles and missions.”

This is so unpredictable. And we've never seen anything quite like this in our lifetime, so there is no playbook here.

Climate change is a national security threat.

When you have a national leader, our national world leader, who has left dignity behind, decency behind, honesty, integrity behind them, that's where you start.

Not everyone at the White House has agreed with me.