Wall Street Journal: The Environmental Protection Agency’s decision to classify rising carbon-dioxide emissions as a hazard to human health is the latest twist in a debate that has raged for decades among politicians, scientists and industry: whether a natural component of the earth’s atmosphere should be considered a pollutant. The EPA’s finding doesn’t say carbon dioxide, or CO2, is by itself a pollutant — it is, after all, a gas that humans exhale and plants inhale. Rather, it is the increasing …