"Global warming" does not necessarily mean a runaway greenhouse effect and global catastrophe a la Venerian persuasion. I think most people realize that the climate machine is filled with feedback mechanisms which can quickly set up a new equilibrium and the planet will soon settle down to a new stable state only a few percent distant from it's present condition. History seems to bear this out, the planet has survived billions of years without a runaway excursion inspite of numerous cosmic impacts, solar flares, volcanic eruptions, continental drifts, and massive lava flows, like the one that created the Deccan Plateau, and glacial periods. The earth climate engine is very stable in the long term.

The concern is that even a minor shift in the climate will cause relatively small shifts in wind and precipitation patterns which may interfere with global agriculture, fisheries, trade routes, which could in turn have disastrous results on our economies. Most of the world's breadbaskets have been gradually adapted and exploited over centuries to meet existing climatic conditions. It is not inconceivable that a global warming (or cooling, for that matter) might suddenly shift major grain or other resource-producing areas. Imagine a world where the Ukraine and the American Midwest are desert, but the Sahara suddenly becomes ideal for wheat cultivation, for example. Or perhaps where the Gulf Stream shifts south to deep-freeze Northern Europe, or where the Monsoon no longer waters Southern Asia.The world would not come to an end, wildlife and nature would adapt, but the political and economic stability of the world would be thrown into turmoil.

No one really knows what might happen, perhaps nothing. Perhaps it would happen anyway, even if we weren't here. But that's the whole point, isn't it? It ain't broke, so don't fix it. And certainly, don't think you can beat on it all you want just because it ain't broke yet.