Some blame can also be apportioned to global warming: thirteen of the fifteen hottest years on record (since the start of record-keeping in 1880) have been since 2000, with 2015 being the hottest year ever recorded. Even though summers are getting hotter, driving up air-conditioner usage nationwide, there have also been some spectacular cold snaps as well, the polar vortex in 2014 being among the most memorable in recent times. All of these extreme weather events, including entire years that are hotter than they should be, cause more crisis points for the grid.
