Obama called for action on climate change during State of the Union

U.S. President Barack Obama mocked congressional Republicans' popular "I am not a scientist" demurral on climate science, and vowed to prevent Congress from undermining his administration's steps to reduce greenhouse gas emissions.

Obama elevated global warming to the top of the list of challenges facing us, saying, "And no challenge — no challenge — poses a greater threat to future generations than climate change."

Here's his retort to the "I'm not a scientist" rhetoric, used by Republican Sen. Marco Rubio and House Speaker John Boehner, among many others. Obama first auditioned these lines during a speech at the University of California at Irvine last year.