As continental glaciers started rolling down from Canada, Siberia and Scandinavia over the temperate regions of the Northern Hemisphere the GOP would be able to claim "See, we told you there was no global warming."

Most people don't realize how much Northern Europe depends on the Gulf Stream to keep the climate moderate there. Look at a map, the UK, Germany and France are as far north as Labrador and Newfoundland. Without the Stream, Europe would return to Ice Age conditions. Of course, global warming would continue as the tropics continued to heat up. The boundary, the Intertropical Convergence Zone, would migrate south, and the weather there would become unstable and chaotic.

The good news is that sea level rise would probably be reversed. If it went on long enough, large portions of the continental shelves would be exposed and shallow water marine ecosystems would collapse: coral reefs, mangrove coasts, tidal biomes, the kelp forests. The world and life would survive, but the planet would look very different. And humanity could fall back on a more sustainable economy: hunter-gathering and slash-and-burn agriculture.