1. We have a climate that is greatly affected by the sun. The sun varies in the amount of light we get from it.
We have truly, absolutely zero ability to modify anything about the sun.
We couldn't even place a probe or device within 10,000 miles of the surface of the sun, if our survival depended on it.
2. Even if the USA cuts their emissions in half tomorrow, with China and India increasing their use of autos and other emissions producing devices, would that be enough? And how exactly is it that USA spends more on reducing emissions while others spend zero? How much of a hit to the economy does this entail, for essentially zero world wide benefit?
How many remember Canada's 180 degree turnaround a few years ago, when they realized that conforming to the Kyoto protocol meant a 10% GDP hit?