Study suggests a new structure for a carbon tax

A new peer-reviewed paper cuts against the grain by concluding that the most effective carbon tax structure should start high and decline over time.

Why it matters: It breaks with carbon tax bills floating around Congress and other proposals that begin modestly and then escalate.

What they found: The paper in the Proceedings of the National Academy of Sciences journal offers several reasons for flipping the script.

• Uncertainty around just how bad damage from climate change could be makes strong near-term steps vital.
• The high costs of delaying action.
• Falling costs of cutting emissions over time as technology improves.

The big picture: The paper's modeling suggests an optimal price would begin at well over $100-per-ton (or even much higher), rise for a few years, and then fall.

"[P]roperly taking climate uncertainty into account leads to the conclusion that we need to take stronger action today to give us breathing room in the event that the planet turns out to be more fragile than current models predict."

Where it stands: It's very different than what's out there now.

• The nonprofit Climate Leadership Council, which includes Big Oil backers, is circulating a plan that starts at $40-per-ton of CO2 and rises annually.
• A Columbia University energy think tank has a helpful tally of Capitol Hill plans that all start with far lower CO2 prices than the PNAS paper suggests.

But, but, but: "Treat carbon in the atmosphere like an asset (with negative payoffs) and apply Financial Economics 101, and its price appears to jump by quite a bit over typically modeled prices," PNAS co-author Gernot Wagner tells me.

Go deeper: Carbon tax campaign unveils new details and backers