I expect this could be controversial for many reasons, not the least of which being that I'm not the environmental scientist in the family. Hopefully my husband will weigh in if I go too far afield. But I ran into a few places today where people talked about global warming as though it means that basically their local temperature will go up, with perhaps some vague mentioning about it being bad for the planet. My thought is - well, not exactly.
The concept of global warming does indicate that the temperature of the planet (in total) is going up. But you have to think about the ecology of the planet, which means you have to think about the systems and how they will react to that. The worst-case scenario is that the extra CO2 in the atmosphere changes the reflective properties of Earth, causing us to absorb more of the sun's radiation, this will cause our ice caps to have excessive melting (already starting, btw), the sea levels to rise and the Deep Atlantic Conveyor - which is driven by the salinity level in it's current - to break down. The conveyor is credited with 'evening out' our climate and creating those temperate climates that we humans love so much and have flourished in. What this means is that the climate will become erratic and that we surface dwellers will actually have to deal with some COLDER temperatures in most of the places we live, with some HOTTER temperatures in the tropical areas.
Now, all that said, I do have two points to make. 1) George Carlin was right, we're not so much worried about the Earth as we are about the environment that makes us comfortable. The Earth has been through worse. So I'm not saying these potential events are catastrophic to the planet, just to the little humans and their favorite friends. 2) Scientists don't know half as much as we hope they did. The human mind seems drawn to absolutes for comfort, but we are nowhere near knowing everything we think we do. But we have developed a pretty good idea that some of our activities are trying to assist the Earth in creating the next ice age. Ice Age was a cute movie, but I think it would suck as a place to live.