Not because it will be necessarily bad, while ours now is good...the kind of changes we can expect from global warning will not be that extreme before the planet adjusts into a new equilibrium.

The world will be worse because it will be different and WE will have to make adjustments to it. Assume the American wheat and corn belts become deserts, but the Sahara makes up for it by becoming a fertile, well-watered plain. Sure, the number of arable hectares may work out to be the same, but populations, markets, cultures, industry and trade will be turned upside down. They will have to adapt. The current American agribusiness industry just can't move to N Africa, along with all the infrastructure needed to support it. At least not overnight.

Keep in mind, the above is just an example, I'm not making any specific predictions. THere's no telling what might happen. Canada and Siberia may become temperate, but Western Europe may become like Labrador. We don't know what will happen but this is just the sort of thing that might happen. If global warming happens, and if it manifests itself the way I expect it to, and if it happens in less than a century, or even less than a lifetime like I expect it might, the world will not become an uninhabitable wasteland. In fact, overall, it may not look that much different than it does now. But locally, the effects will be catastrophic. Areas now highly populated will have to be evacuated, and areas now mostly empty will become prizes everyone will want. Political and economic structures which have taken centuries to adapt to current geography will suddenly have to be reorganized, or move.

This is what's scary about global warming. Not that the world will become uninhabitable, the earth has easily survived catastrophes much worse than a minor change in temperature, and there are many feedback mechanisms operating to keep it from a runaway excursion. We will not become like Venus or Mars. But the finely tuned civilization we have built over centuries will have to adapt to new conditions over a period of just a few decades. We're going to wake up one morning with all our assests in the wrong places.