Climate Change Economics

This paper is an introduction to, “The EMF 32 Study on U.S. Carbon Tax Scenarios,” part of the Stanford Energy Modeling Forum (EMF) Model Inter-comparison Project (MIP) number 32. Eleven modeling teams participated in this study examining the economic and environmental impacts of various carbon tax trajectories and differing uses of carbon tax revenues. This special issue of Climate Change Economics documents the results of this study with four cross-cutting papers that summarize results across models, and ten papers from individual modeling teams.

The Energy Modeling Forum (EMF) 32 study on carbon tax scenarios analyzed a set of illustrative policies in the United States that place an economy-wide tax on fossil-fuel-related carbon dioxide (CO${}_2)$ emissions, a carbon tax for short. Eleven modeling teams ran these stylized scenarios, which vary by the initial carbon tax rate, the rate at which the tax escalates over time, and the use of the revenues. Modelers reported their results for the effects of the policies, relative to a reference scenario that does not include a carbon tax, on emissions, economic activity, and outcomes within the U.S. energy system. This paper explains the scenario design, presents an overview of the results, and compares results from the participating models. In particular, we compare various outcomes across the models, such as emissions, revenue, gross domestic product, sectoral impacts, and welfare.

The Stanford Energy Modeling Forum exercise 32 (EMF 32) used 11 different models to assess emissions, energy, and economic outcomes from a plausible range of economy-wide carbon price policies to reduce carbon dioxide (CO${}_{\mathrm{\text{2}}})$ emissions in the United States. Here we discuss the most policy-relevant results of the study, mindful of the strengths and weaknesses of current models. Across all models, carbon prices lead to significant reductions in CO₂ emissions and conventional pollutants, with the vast majority of the reductions occurring in the electricity sector. Importantly, emissions reductions do not significantly depend on the rebate or tax cut used to return revenues to the economy. Expected economic costs, as modeled by either GDP or welfare, are modest, but vary across models. These costs are offset by benefits from avoided climate damages and health benefits from reductions in conventional air pollution. Using revenues to reduce preexisting capital or labor taxes reduces costs in most models relative to lump-sum rebates, but the size of the cost reductions varies significantly. Devoting at least some revenue to household rebates can significantly reduce adverse impacts on low income households. Carbon prices at $25/ton or even lower levels cause significant shifts away from coal as an energy source with responses of other energy sources highly dependent upon technology cost assumptions. Beyond 2030, we conclude that model uncertainties are too large to make quantitative results useful for near-term policy design. We close by describing recommendations for policymakers on interacting with model results in the future.

This paper presents a multi-model assessment of the distributional impacts of carbon pricing. A set of harmonized representative CO₂ taxes and tax revenue recycling schemes is implemented in five large-scale economy-wide general equilibrium models. Recycling schemes include various combinations of uniform transfers to households and labor and capital income tax reductions. Particular focus is put on equity — the distribution of impacts across household incomes — and efficiency, evaluated in terms of household welfare. Despite important differences in the assumptions underlying the models, we find general agreement regarding the ranking of recycling schemes in terms of both efficiency and equity. All models identify a clear trade-off between efficient but regressive capital tax reductions and progressive but costly uniform transfers to households; all agree upon the inferiority of labor tax reductions in terms of welfare efficiency; and all agree that different combinations of capital tax reductions and household transfers can be used to balance efficiency and distributional concerns. A subset of the models go further and find that equity concerns, particularly regarding the impact of the tax on low income households, can be alleviated without sacrificing much of the double-dividend benefits offered by capital tax rebates. There is, however, less agreement regarding the progressivity of CO₂ taxation net of revenue recycling. Regionally, the models agree that abatement and welfare impacts will vary considerably across regions of the U.S. and generally agree on their broad geographical distribution. There is, however, little agreement regarding the regions which would profit more from the various recycling schemes.

This paper provides a detailed, cross-model analysis and discussion of the implications of carbon tax scenarios on changes in sectoral output, energy production and consumption and the competitiveness of the United States’ economy. Our analysis focuses on the broad patterns apparent across models in both qualitative and quantitative terms at the sector level, with a focus on energy-intensive, trade-exposed sectors. We identify how variations in carbon tax trajectories and different options for using the revenue from the tax drive these results.

I examine the general equilibrium costs of climate policies that levy taxes on carbon dioxide (CO₂) emissions in the United States and return the revenue in the form of lump-sum rebates and tax relief over the years 2020 to 2040 using the US regional version of the Applied Dynamic Analysis of the Global Economy (ADAGE-US) forward-looking dynamic Computable General Equilibrium (CGE) model. I approximate the value of co-benefits to these policies that arise from concomitant reductions in nongreenhouse gas (GHG) emissions using the CO-Benefits Risk Assessment model (COBRA). There is significant heterogeneity in costs and co-benefits from climate policies across space and income. Policy costs are generally less than 0$.$5% in equivalent variation terms (between a few tens of dollars and several hundred per household, depending on the income quintile), can be fully neutralized for the lowest- quintile households at a modest increase in overall policy cost, and tend to be lower for upper-quintile households in coastal regions. The policy co-benefit values range widely across regions, approximately $150–1250 per household, exceeding the gross cost of the policy for many households, particularly those in the Midwest. Last, I identify a marginal welfare cost of $58$∕$tCO₂ and a marginal co-benefit of $31$∕$tCO₂ at a national level over all households, which implies a required climate benefit of $27$∕$tCO₂ or less to justify the level of abatement achieved by a $25$∕$tCO₂ tax growing at 5%.

We examine the lifetime incidence and intergenerational distributional effects of an economy-wide carbon tax swap using a numerical dynamic general equilibrium model with overlapping generations of the U.S. economy. We highlight various fundamental choices in policy design including (1) the level of the initial carbon tax, (2) the growth rate of the carbon tax trajectory of over time, and (3) alternative ways for revenue recycling. Without revenue recycling, we find that generations born before the tax is introduced experience smaller welfare losses, or even gain, relative to future generations. For sufficiently low growth rates of the tax trajectory, the impacts for distant future generations decrease over time. For future generations born after the introduction of the tax, the negative welfare impacts are the smallest (largest) when revenues are recycled through lowering pre-existing capital income taxes (through per-capita lump-sum rebates). For generations born before the tax is introduced, we find that lump-sum rebates favor very old generations and labor (capital) income tax recycling favors very young generations (generations of intermediate age).

This paper examines impacts of nationally-imposed carbon taxes on different regions of the United States. The goal is to see what can be learned about the drivers of regional political support for and opposition to such measures. Whether at the state, regional or national levels, carbon taxes are one option for reducing greenhouse gas emissions; several state and regional programs are already under way and lowering emissions. This analysis uses a U.S. regional version of the DIEM computable general equilibrium model to explore relationships between carbon taxes, emissions, and economic growth. One area of emphasis is how the distribution of impacts may be affected by differences in regional household spending patterns, the types of industries and electricity generation situated in those regions, and the locations of energy production and energy-intensive manufacturing. The modeling also explores how carbon tax revenues can be used to offset impacts on regional factor earnings.

Carbon pricing generates revenues which can be recycled back into the economy in different ways to help mitigate the economic cost of abatement. These include, lump-sum transfers to households; reducing existing distortionary taxes, such as income taxes on labor and capital; investment in technology funds leading to energy/emissions efficiency improvements; and/or infrastructure developments that help expedite the adoption of low or lower carbon-intensive technologies. In this paper, we undertake illustrative simulations to explore how different revenue recycling options influence the overall economic outcome in terms of broad macroeconomic indicators, such as Gross Domestic Product (GDP) or household welfare. Environment and Climate Change Canada’s (ECCC) multi-sector, multi-region Computable General Equilibrium (CGE) model (EC-MSMR) is used to simulate various revenue recycling options. These simulations are undertaken for the U.S. economy. The main findings of the paper are: (i) using carbon revenue for a general income tax reduction or investment subsidy is more advantageous than a lump-sum transfer to U.S. consumers in terms of welfare or GDP; and (ii) using carbon revenue for a sector-based subsidy such as renewable energy is more disadvantageous than a lump-sum transfer to consumers. In terms of accumulated welfare effects, our results indicate that the best carbon revenue recycling option is the investment subsidy or capital income tax reduction in the longer horizon; labor tax reductions yield the best outcome in the shorter horizons.

This paper documents application of the Future Agricultural Resources Model (FARM) to stylized carbon tax scenarios specified by the Stanford Energy Modeling Forum (EMF). Model results show that the method of tax revenue recycling makes a difference. Either labor-tax, or capital-tax, recycling can reduce the welfare cost of a carbon tax policy relative to lump sum recycling. Of the two tax recycling options, reducing capital taxes provides the greater reduction in welfare costs. However, carbon tax revenues decline with stringent carbon dioxide (CO₂) emission targets and the availability of a negative-emissions technology such as bio-electricity with CO₂ capture and storage (BECCS). As BECCS expands, net carbon tax revenues peak and decline due to an offsetting subsidy for carbon sequestration, limiting the potential for labor- or capital-tax recycling to reduce welfare costs of a climate policy.

This paper examines carbon tax design options in the United States using an intertemporal computable general equilibrium model of the world economy called G-Cubed. In this paper, we discuss four policy scenarios that explore two overarching issues: (1) the effects of a carbon tax under alternative assumptions about the use of the resulting revenue, and (2) the effects of a system of import charges on carbon-intensive goods (“border carbon adjustments” or BCAs).

Consistent with earlier studies, we find that the carbon tax raises considerable revenue and reduces CO₂ emissions significantly relative to baseline, no matter how the revenue is used. Gross annual revenue from the carbon tax with lump sum rebating and no BCA begins at $110 billion in 2020 and rises gradually to $170 billion in 2040. By 2040, annual CO₂ emissions fall from 5.5 billion metric tons (BMT) under the baseline to 2.4 BMT, a decline of 3.1 BMT, or 57%. Cumulative emissions over 2020 to 2040 fall by 48 BMT.

Also consistent with earlier studies, we find that the carbon tax has very small overall impacts on gross domestic product (GDP), wages, employment, and consumption. Different uses of the revenue from the carbon tax result in slightly different levels and compositions of GDP across consumption, investment and net exports. Overall, using carbon tax revenue to reduce the capital income tax rate results in better macroeconomic outcomes than using the revenue for lump sum transfers.

Counter to their purported purpose of protecting U.S. trade strength, for a given revenue policy, BCAs tend to produce lower net exports than the carbon taxes alone. This is generally because the BCAs raise the value of the dollar relative to other currencies, thus lowering exports more than they lower imports. This is consistent with standard results in the international trade literature on the effects of import tariffs and export subsidies on real exchange rates, a result that is often overlooked in the discussion of domestic carbon policy.

In a finding new to the literature, our results show that BCAs can have strikingly different effects depending on the use of the revenue. Under a lump sum rebate, BCAs exacerbate the impact of the carbon tax by lowering domestic output further than it would fall under the carbon tax alone. Under a capital tax swap, however, BCAs have a moderating effect: they reduce the impact of the tax on most industries.

Future carbon dioxide (CO₂) emissions under a carbon tax depend on the time-path of the economy under baseline (business-as-usual) conditions as well as the extent to which the policy reduces emissions relative to the baseline. Considerable uncertainties surround the baseline forecasts for fuel prices, energy efficiency (energy-GDP ratios), and GDP, as evidenced by the significant ranges in the forecasts by government agencies and research institutions in the U.S. This paper assesses the significance of these uncertainties to the path of CO₂ emissions under a carbon tax. We do this by examining the emissions levels and quantities of abatement that result from the E3 general equilibrium model under a range of alternative baseline forecasts for fuel prices, energy efficiency, and GDP, where the different baselines are produced through suitable changes to key model parameters. In addition, we consider how the time-profile of the carbon tax needed to achieve specified CO₂ abatement targets is affected by such forecast-linked changes in parameters.

We find that the sensitivity of baseline emissions to alternative forecasts depends on the particular forecasted variable under consideration. Baseline CO₂ emissions are highly sensitive to alternative scenarios related to the rate of energy efficiency improvements in the nonenergy sector and the rate of general economic growth. In contrast, such emissions are much less sensitive to alternative scenarios related to the productivity of fossil fuel production. The extent of abatement from the baseline is generally fairly insensitive to changes in the scenarios for time-paths of fuel prices, energy-efficiency and GDP. We also find that short-term emissions targets can be achieved with relatively moderate carbon taxes under all of the baseline scenarios considered.

For EMF 32, we applied a new version of our Intertemporal General Equilibrium Model (IGEM) based on the North American Industry Classification System (NAICS). We simulated the impacts arising from the Energy Modeling Forum’s broad range of carbon taxes under three revenue recycling options — lump sum redistributions, capital tax reductions, and labor tax cuts. We examined their consequences for industry prices and quantities, for the overall economy, and for the welfare of households, individuals, and society, the latter in terms of efficiency and equity. We rank recycling mechanisms from most to least favorable in terms of the magnitudes of their impacts on net social welfare — efficiency net of equity — recognizing that other objectives may be more important to policy makers and the public. Finally, we and the EMF 32 effort focus only on the economic effects of carbon taxation and revenue recycling; the environmental benefits arising from emissions reductions are not within our scope of study.

We find CO₂ emissions abatement to be invariant to the chosen recycling scheme. This means that policy makers need not compromise their environmental objectives when designing carbon tax swap options. We also find additional emissions reductions beyond the scope of coverage and points of taxation.

Reducing capital taxes promotes new saving, investment and capital formation and is the most favorable recycling mechanism. In 2010 dollars, the welfare loss per ton abated ranges from $0.19 to $3.90 depending on the path of carbon prices. Reducing labor taxes promotes consumption and work through real-wage incentives and is the next most favorable recycling scheme. Here, the welfare loss per ton abated ranges from $11.09 to $16.49 depending on the carbon tax trajectory. Lump sum redistribution of carbon tax revenues is the least favorable recycling option. It incentivizes neither capital nor labor. Consequently, the damages to the economy and welfare are the greatest among the three schemes. With lump sum recycling, the welfare loss per ton abated ranges from $37.15 to $43.61 as carbon taxation becomes more aggressive. While this ranking is common among the participating EMF 32 models, the spread in our results is the greatest in comparison which we attribute to the substitution possibilities inherent in IGEM’s econometrics, the absence of barriers to factor mobility, and likely differences in the manner in which tax incentives are structured.

We find welfare gains are possible under capital and labor tax recycling when emissions accounting is viewed from a top-down rather than a bottom-up perspective and carbon pricing is at an economy-wide average. However, these gains occur at the expense of abatement.

We find capital tax recycling to be regressive while labor tax recycling is progressive as is redistribution through lump sums. Moreover, we find that the lump sum mechanism provides the best means for sheltering the poorest from the welfare consequences of carbon taxation. Thus, promoting capital formation is the best use of carbon tax revenues in terms of reducing the magnitudes of welfare losses while the lump sum and labor tax options are the best uses for reducing inequality.

We show results from the National Energy Modeling System generated during the Energy Modeling Forum 32 study — focusing on macroeconomic responses to different methods of recycling carbon tax revenue. We find that recycling such revenue directly to consumers in the form of lump sum payments results in smaller negative GDP impacts than using the revenues to reduce business taxes.

This paper provides a comprehensive exploration of the impacts of economy-wide CO₂ taxes in the U.S. simulated using a detailed electric sector model [the National Renewable Energy Laboratory’s Regional Energy Deployment System (ReEDS)] linked with a computable general equilibrium model of the U.S. economy [the Massachusetts Institute of Technology’s U.S. Regional Energy Policy (USREP) model]. We implement various tax trajectories and options for using the revenue collected by the tax and describe their impact on household welfare and its distribution across income levels. Overall, we find that our top-down/bottom-up models affects estimates of the distribution and cost of emission reductions as well as the amount of revenue collected, but that these are mostly insensitive to the way the revenue is recycled. We find that substantial abatement opportunities through fuel switching and renewable penetration in the electricity sector allow the economy to accommodate extensive emissions reductions at relatively low cost. While welfare impacts are largely determined by the choice of revenue recycling scheme, all tax levels and schemes provide net benefits when accounting for the avoided global climate change benefits of emission reductions. Recycling revenue through capital income tax rebates is more efficient than labor income tax rebates or uniform transfers to households. While capital tax rebates substantially reduce the overall costs of emission abatement, they profit high income households the most and are regressive. We more generally identify a clear trade-off between equity and efficiency across the various recycling options. However, we show through a set of hybrid recycling schemes that it is possible to limit inequalities in impacts, particularly those on the lowest income households, at relatively little incremental cost.