Conventional wisdom holds that the efficient way to limit warming to a chosen level is to price carbon emissions at a rate that increases exponentially. We show that this "Hotelling" tax on carbon emissions is actually inefficient. The least-cost policy path takes advantage of the climate...

I show that commonly proposed emission taxes are not optimal for controlling climate change: they can achieve zero emissions but cannot induce negative emissions. The first-best policy charges firms period by period for leaving a stock of carbon in the atmosphere, not just for injecting carbon...

I analyze a novel climate policy instrument that attaches a transferable asset to each unit of carbon in the atmosphere. I show that this instrument improves on an emission tax by incentivizing both optimal emission reductions and optimal removal of past emissions. Emitters post a bond equal to...