Reasonable people may disagree about what policies will best fight climate change. But climate science makes one thing clear: The planet must limit carbon emissions, or face a bleak future. And we will never get there unless we make policy changes that align market incentives with this goal. It’s economics 101. There’s no way to avoid making polluters pay for the damage they cause, or they’ll keep causing it. That either starts with a price on carbon or, ideally, a cap on carbon emissions.