Retiring Sen. Lamar Alexander (R-Tenn.) said on the Senate floor Monday that he believes climate change is real and that human emissions of greenhouse gases are a major cause — but that Democrats' "Green New Deal" is "so far out in left field that no one is going to take it seriously."

Why it matters: Alexander proposed a plan of his own called "The New Manhattan Project for Clean Energy," which argues that the United States' "extraordinary capacity for basic research" should be used to combat "10 Grand Challenges" in the next five years. Alexander said that meeting these challenges "would create breakthroughs in advanced nuclear reactors, natural gas, carbon capture, better batteries, greener buildings, electric vehicles, cheaper solar and fusion."

Alexander's 10 Grand Challenges