They have little backing. The 30 governments that have ratified it DO have the backing of their electorates. The atmospheric destabilization that's typical for GHGs is different from effects of solar spots.
Volcanoes see below.
You're quite right. In a technical sense they also require major changes. Well, I don't know what Bush's real motivation is. On some subjects the voters are too uninformed to make sensible decisions. This opens the door to vested interests.