no no... that story supports the removal of cats. see, cats convert unburnt hydrocarbons, nitrogen oxide and carbon monoxide into carbon DIoxide. so what we get is less smog and less acid rain, but a whole lot more carbon dioxide... the stuff that's leading to the melting of polar ice caps. when a hydrocarbon burns, it produces carbon dioxide and water as byproducts, but since our engines cannot burn all of the gasoline, there are "other" products that result.
so now do we let our cars emit carbon monoxide (that cannot be reformed into oxygen through plants) or do we keep both cats and have them convert these byproducts to carbon dioxide? maybe we shouldn't be clear cutting so much forest then? it's a smoggy situation, to say the least.