Our discussion continues with David Doniger, Natural Resources Defense Council senior attorney, who notes that flexible market-based emissions cap-and-trade programs have been applied somewhat ubiquitously to address a range of environmental issues, from eliminating lead in gasoline, to combatting acid rain, to phasing out ozone-depleting chemicals – even to allocating catch limits for herring, an issue incidentally connected to cases now pending before the Supreme Court challenging the long-standing legal precedent known as the Chevron doctrine.

But Congress and the Supreme Court have rejected attempts to apply this flexible market-based approach to controlling greenhouse gas emissions. Today, few in Washington even attempt to suggest emissions cap-and-trade as a response to greenhouse warming, and instead call for Congress to put a "price" on carbon. But Doniger notes that putting a price on carbon involves establishing a new tax, and he doesn't see a carbon tax gaining traction among Republicans in Congress.

"I don't think we're going to see carbon taxes because the one whole party has become the anti-tax party. It's a dead letter to one whole party," Doniger says. But he does see merit to cap-and trade, and points to bipartisan congressional agreement in 2017 to employ cap-and-trade in phasing down ozone-depleting HFCs. 

"There is life in the old cap-and-trade design yet," Doniger says. "There are variations of emissions trading that we continue to promote because the flexibility reduces costs for industry and therefore lets them reach farther for the same total regulatory costs."