Polluting Non-Renewable Resources, Carbon Abatement and Climate Policy in a Romer Growth Model

We study how the availability of an abatement technology affects the optimal use of polluting exhaustible resources, and optimal climate policies. We develop a Romer endogenous growth model in which the accumulated stock of greenhouse gas emissions harms social welfare. Since the abatement technology allows reducing the effective pollution for each unit of resource use, extraction and pollution are partially disconnected. Abatement accelerates the optimal extraction pace, though it may foster CO2 emissions for the early generations. Moreover, it is detrimental to output growth. Next, we study the implementation of a unit tax on carbon emissions. Contrary to previous results of the literature, its level here matters, as it provides the right incentives to abatement effort. When it is measured internal good, the optimal (Pigovian) carbon tax is increasing over time, while it is constant when expressed in utility. Moreover, it can be interpreted ex-post as a decreasing ad-valorem tax on the resource. Finally, we study the impact of the climate policy on the decentralized equilibrium: in particular, it fosters both the intensity and the rate of carbon abatement. In the near-term, it spurs research and output growth, while decreasing output level.

Climate Change Mitigation Options and Directed Technical Change: A Decentralized Equilibrium Analysis

The paper considers a climate change growth model with three R&D sectors dedicated to energy, backstop and CCS (Carbon Capture and Storage) efficiency. First, we characterize the set of decentralized equilibria: A particular equilibrium is associated to each vector of public tools which includes a carbon tax and a subsidy to each R&D sector. Moreover, we show that it is possible to compute any equilibrium as the solution of a maximization program. Second, we solve the first-best optimum problem and we implement it by computing the vector of optimal tools. Finally, we illustrate the theoretical model using some calibrated functional specifications. In particular, we investigate the effects of various combinations of public policies (including the optimal ones) by determining the deviation of each corresponding equilibrium from the "laisser-faire" benchmark.climate change, energy, CCS, directed technical change, carbon tax, R&D subsidies