No, it is not the global warming/ice age plot of The Day After Tomorrow that frightens me the most. It is this scene:
Snow/icebound with others (including some whiz kids) in the New York Public Library, the character played by Jake Gyllenhaal suggests that they burn library books to keep them warm. Never mind that they are in a room with wooden walls and wooden bookshelves (and wood gives off more warmth than books when burned!). Then some whiz kids engage in a debate on which works by whose authors to burn!
The horror! The terror I felt as I watched those precious being burned! Up to now, I still remind myself - It's ONLY a movie!