There two types of air pollution, the first one is the type that all the scientists are moaning about at the moment the CO2 type that's causing global warming. The second type is made of much bigger particles and is basically smoke; this bounces the sunlight off and causes global cooling.
Now in centuries past there was an equal amount of heating pollution and cooling pollution so the planet stayed in balance where the planet wasn't really heating up or cooling down. The problem now is thanks to the Clean Air Act 1956 all of the global cooling pollution was cured so then there was a great imbalance and so the planet now is warming up.
