Implementation of many policies intended to reduce fuels’ contribution to global warming require an estimate of the global warming intensity (GWI) of various fuels. Determining the climate effect of a direct substitution of fuels is not the same as determining the official value of each...

We analyze the policy implications of aversion to Knightian uncertainty (ambiguity) about the possibility of tipping points. We demonstrate two channels through which uncertainty aversion affects optimal policy in the general setting. The first channel relates to the policy's effect on the...

I analyze the marginal value of reducing greenhouse gas emissions (the "social cost of carbon") under uncertainty about warming, under uncertainty about how much warming reduces consumption, and under stochastic shocks to consumption growth. I theoretically demonstrate that each of these sources...

We find that plug-in hybrid electric vehicles (PHEVs) could significantly reduce automotive greenhouse gas (GHG) emissions and petroleum consumption, while improving energy security and urban air quality. Widespread PHEV adoption will depend upon technological and economic advances in batteries...

We analyze the efficient subsidy for durable good technologies. We theoretically demonstrate that a policymaker faces a tension between intertemporally price discriminating by designing a subsidy that increases over time and taking advantage of future technological progress by designing a...