The following editorial appeared in the Philadelphia Inquirer on Thursday, June 29:

“Carbon dioxide: It’s what we breathe out and plants breathe in. They call it pollution; we call it life.”

That paradox expressed by the free-market Competitive Enterprise Institute is being used to counter former Vice President Al Gore’s scary global warming documentary, “An Inconvenient Truth.”

How could a life-giving gas be dangerous to our planet? What right does a president or Congress have to regulate it as if it were smog, acid rain or arsenic?

Those are the central questions the U.S. Supreme Court agreed to answer by hearing Massachusetts v. Environmental Protection Agency next fall. It could be the most significant environmental case ever to come before the court.

The justices will decide whether the Clean Air Act requires the government to regulate carbon dioxide, which contributes to global warming, when it’s emitted from vehicles. The ruling could influence power-plant regulation as well.

Beyond federal policy, at stake are plans in 11 states, including Pennsylvania and New Jersey, to tighten vehicle emissions to improve air quality and fuel efficiency.

The nation needs more clarity on complicated environmental issues than the high court offered last week in a murky 4-4-1 wetlands decision. In typical hair-splitting, four justices wanted to reduce federal protection of wetlands; four backed more protection; and Justice Anthony Kennedy suggested case-by-case analysis. How will landowners, environmental groups, and government agencies proceed under those clear-as-bog-mud guidelines? Expect more lawsuits.

In the carbon-dioxide case, the three District of Columbia Circuit Court judges split three ways. Ice caps won’t stop melting while judges cogitate over global warming. Congress may need to step in.

The Clean Air Act specifies some pollutants for regulation, but not carbon dioxide. The act does allow the Environmental Protection Agency to regulate any pollutant that affects the “welfare” of “soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility and climate, and damage to and deterioration of property.” Global warming, caused, in part, by carbon dioxide coming from vehicles, is having those negative effects.

EPA already regulates other naturally occurring substances. Phosphorus, for example, is a critical nutrient for plants, but it’s regulated because in excessive quantities, it kills life in lakes and streams. Likewise, carbon dioxide, in excessive quantity, is hurting the planet.

Yes, the Earth needs carbon dioxide, but only so much. When the supply begins to endanger public health, government should act.

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