I'm fairly ignorant in terms of the science behind this, and one thing in the article raises some questions for me:

  > Sea level has risen a lot — 10 to 20 meters — in warm
  > periods in the past

Presumably this is in the distant, pre-industrial past. If so, what caused the warm period and, assuming sea level subsequently dropped afterwards, what caused the warm period to end? Other than human activity contributing to the current warm period, why is it different than previously?