What could happen?
Well
The Day After Tomorrow had examples of what could happen. Here is a list of things that could happen; some of them were shown in the movie.
Sea levels would indeed rise due to the heating of the oceans, and the melting of the glaciers and sea ice.
Because of this, cities on coasts would flood.
Droughts, hotter, and or drier weather may appear in places that receive lots of rain/snowfall.
Say goodbye to lakes, rivers, and pounds. Because they could indeed dry up.
Due to the increase of droughts, it would be hard to grow crops, and there wouldn’t be as much water for drinking,
and showers.
Some animals and plants couldn’t survive because of the heat, so they might become extinct.
Powerful storms like tornadoes, hurricanes, and thunderstorms would get more common because of the change
in heat and water evaporation.