FLOODS
Although a significant increase in global warming would likely increase the magnitude of all manner of natural disasters, one can be sure that the danger of huge floods would increase exponentially.
This is a picture from 1993, when the Mississippi River flooded.
One of the most popular theories concerning global warming is that, eventually, it will melt the polar ice caps. Although the temperature of the earth would have to rise much more than it has by now, if global warming were to get so serious that the polar ice caps, or any other large segments of ice, melted, it would result in devastating and seriously life-threatening floods.
What's even worse is that these floods could do more than just make people homeless or dead. If the polar ice caps were to truly melt, oceans would overflow. Large portions of land would be flooded. This would be very serious.
Not all theories about the polar ice caps are correct. No matter how serious the melting problem gets, there simply isn't enough water contained in the caps to cause a disaster of the magnitude seen in the Kevin Costner bomb "Waterworld."