Natural gas’s displacement of carbon-rich, toxic coal as the country’s top electric fuel source would have seemed a preposterous dream just a decade ago. It has come about with no government mandate and while saving consumers money. When the market demands an outcome, things change fast.

But even substantial reductions in greenhouse-gas emissions in the long term will not be enough to head off catastrophic climate change. The transition from coal to natural gas has been beneficial. But society must eliminate its carbon dependency. It cannot burn vast amounts of any fossil fuel for “decades and decades,” as Mr. Farrell hopes, unless there is a revolution in emissions capture technology. Even in the short term, U.S. emissions are rising, despite the restraint that stepped-up natural-gas burning has provided. The government must demand more change, more quickly.

Putting the planet first requires accepting both insights. The government should insist on cutting emissions but, to the largest extent possible, decline to dictate how, instead setting incentives and standards that unleash public and private effort.