Extreme weather: Are the recent storms and droughts unprecedented?

      |As another major storm hits the South and the East, sub-zero temperatures still grip the Midwest, Northern California received about 20 inches of rain - though that won't be enough to end the state's drought emergency. Michio Kaku, a physics professor at the City College of New York and a CBS News contributor, talks to the "CBS This Morning" co-hosts about the reasons for the extreme weather.