The earth is a tiny little ball surrounded by and affected by the enormous energy generating forces of outer space (which include constant gama ray bombardment) and sun spots, not to mention the humungous heat generating power of volcanoes and ocean currents.
It is arrogance of the highest magnitude to think that mankind, who is akin to an amoeba on the butt of an elephant, can affect the earth's climate to any signifigant degree.
Yes, it might be a few degrees hotter in the city (due to heat retention in cement) and we might be able to warm up the atmosphere a tiny fraction if we were to light all the forests on fire at once.
But in the end, wouldn't most of the heat dissapate into outer space. And wouldn't the constant action of evaporation and rainfall continue to cleanse the earth of any particulates which would possibly be a detriment.
If there was ever a Jekyll-Hyde politician it's Arnold. Sometimes he makes me happy I live in the People's Republic of California and other times---like after reading this idiotic idea---I'm ready to pack up and move, but where???? ;)