Climate Policy

With the nation’s borrowing limit looming, Washington is struggling to find a solution to America’s mounting debt. The Bi-Partisan Tax Commission laid out the harsh reality in a 2010 report: Closing the deficit would require both tax increases and cuts to social programs such as Medicare, Medicaid and Social Security. But a new study out of MIT shows there may be another alternative to stave off some of what would be difficult tradeoffs.

We outline a benchmark carbon dioxide (CO2) intensity system with tradable permits for the aviation industry that will incent in-sector emission abatement opportunities that cost less than the social cost of carbon (SCC). The system sets benchmark emission intensities (CO2 emissions per revenue ton kilometer) by route group and facilitates flexibility in meeting the benchmarks by allowing airlines to sell permits if they operate more efficiently than the benchmarks, and buy permits if they do not meet the benchmarks. The CO2 benchmark system could operate concurrently with existing measures to mitigate aviation CO2 emissions, will reduce the number of offsets needed to achieve carbon-neutral growth, and provide another (optional) lever to address fairness issues in climate regulations. Moreover, by providing a blueprint for other industries to price marginal emissions at the SCC, a CO2 benchmark system could preserve the ‘carbon budget’ for use by high-cost abatement industries such as the aviation industry. 

A primary reason for implementing a carbon or greenhouse gas tax is to reduce emissions, but in recent years there has been increased interest in a carbon tax’s revenue potential. This revenue could be used for federal deficit reduction, to help finance tax reform, support new spending priorities such as infrastructure spending, offset the burden of the tax on households, or other purposes. With an environmental goal to reduce emissions to very low levels, programs that become dependent on the revenue may come up short when and if carbon revenue begins to decline. To date, the revenue potential of a carbon tax has not been studied in detail. This study focuses on how much carbon tax revenue can be collected and whether there is a carbon “Laffer Curve” relationship, with a point where revenue begins to decline. We employ the MIT U.S. Regional Energy Policy (USREP) model, a dynamic computable general equilibrium model for the U.S. economy, for the numerical investigation of this question. We consider scenarios with different carbon prices and emissions reductions goals to explore how they may affect whether and at what tax rate revenues peak. We find that a sufficiently high tax rate would induce a revenue peak between now and 2050. For the scenarios we study, however, we find that carbon tax revenue is a dependable source of revenue to finance federal fiscal initiatives over a thirty-year period at the minimum. We also explore how the cost of low-carbon technology and existing energy policies interact with tax rates and revenues. Our results indicate that lower costs of abatement technology make emissions more responsive to the tax rate, and removing regulations on renewables and personal transportation results in more carbon tax revenues. Our results also show that either lowering technology costs or removing existing policies would reduce the welfare cost of a carbon policy with specific reduction goals, with a larger offsetting gain from eliminating distortions associated with existing policies.

We estimate Engel Curves based on Chinese household microdata and show in general equilibrium simulations that they imply substantially lower energy demand and CO2 emissions, relative to projections based on standard assumptions of unitary income elasticity. Income-driven shifts in consumption reduce the average welfare cost of emissions pricing by more than half. Climate policy is also less regressive, as rising income leads to rapid convergence in the energy intensity of consumption baskets and more evenly distributed welfare loss across households. Our findings underscore the importance of correctly accounting for the relationship between income and energy demand in high-growth economies.

A new study by MIT climate scientists, economists, and agriculture experts finds that certain hotspots in the country will experience severe reductions in crop yields by 2050, due to climate change’s impact on irrigation.

The most adversely affected region, according to the researchers, will be the Southwest. Already a water-stressed part of the country, this region is projected to experience reduced precipitation by midcentury. Less rainfall to the area will mean reduced runoff into water basins that feed irrigated fields.

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