I haven't read all pages, stoped somewhere on page 3. But, I've seen people typing that it would be incorrect that call it Global Warming, and that they should use the term Nuclear Winter instead. Because that is what would follow from a global nuclear war. While this is correct, a nuclear winter would never be that long, it would only affect some parts of the world, following the wind current and not be longer than maybe a few months. Within this time, it will of course be cold, but when the nuclear dust settles, the sun will reach the surface and heat the earth again, and its here a global scale warming will begin, since the nukes probably will damage the ozon layer ALOT, increasing the UV-heatning/radiation tremendous.
Edit: I should add, that after a warm period, that would come after a while, there will be a ice age, its the natural cycle, and then the climate will even out, and then it will restart again. It has to do with the natures will to disturb things, because of the sun, the climate will never be stable. We, us, (humans), just speeds it up a bit.
Edit 2.0: It would be very cool to see a ice age effect in CIV4 with the new 3D engine, it could be done very cool I think. Feeling the ice crawl down, and over the sphere.
Sorry for bad english, tired as hell now.