The Earth's climate is cyclical, fact. The Earth will have another ice age.
Whether we affect it or not is open to debate.
Global warming causing another ice age may seem counter intuitive but it makes a lot of sense. The way it would affect the deep ocean circulation as mentioned in the film.
The super cold hurricanes were complete BS, hurricanes happen because there is to much heat in the ocean's surface waters. A storm has to have energy, heat is energy.
This could not happen in the time frame portrayed in the movie. Heat is energy, it has to go somewhere, radiate in to space or whatever. For one gram (about one ml) of water to lower one degree C one calory of energy has to be removed from it, that energy has to go somewhere. For the Gulf Stream/ North Atlantic current to drop 13 degrees, (how many ml of water is that??? you do the math) that energy would have to go somewhere. Where???
I'm not a professional climatologist, just a half assed marine scientist.