Ok, ethanol combusts to produce CO2 and H2O. The theory of global warming (yes, theory) is based on the idea that CO2 is a 'greenhouse gas'. So by burning something with carbon in it (and assuming that global warming is real) we are not solving this matter.
On another note. Ethanol-based gasolines (such as BP gas or E-85) are not only engine-corrosive, but significantly less fuel efficient (I think I remember hearing E-85 being 20% less mpg than standard unleaded). It's also only 10 cents (less than 5%) cheaper than regular 87 gasoline.
In closing, ethanol-based fuels are not only more expensive (as costs per distance you can drive with it) and bad for your engine, but they really don't offer much of a solution from an environmental standpoint.........E-85 SUCKS!!!!!!