I see there is a new study which attempt to quantify the full cost of the Iraq war. The best estimate seems to be $1.8 trillion. Compare this with the cost of the Kyoto protocol, which has been derided by right wingers for years as too expensive. It's cost was estimated at 56 billion-427 billion by 2010.
Not to mention that the Kyoto protocol would, umm, fight global warming, whereas whether the Iraq war will ever benefit the US or Iraq depends on the success of the US project there, which is currently uncertain.