We know that we are contributing to global warming. What we do not know is whether we are the sole cause of global warming. Remember, the planet has gone through an ice age before, and dinosaurs didn't drive Hummers.

What should be done to fight global warming, is to levy taxes on all items that are inefficiently emitting co2 (example: cars that get less than 20 mpg), and simultaneously increase subsidies for technologies like solar and wind power.

Once solar, wind and other alternative energy technologies mature, the cost will go down, which will allow them to compete in a free market with oil.

And once alternative energies are able to compete in a free market with oil, we will be able to pass this technology along to developing countries.