Publications by Author: Metcalf, Gilbert

2020
Metcalf, Gilbert, and James H. Stock. “Measuring the Macroeconomic Impact of Carbon Taxes.” Harvard Environmental Economics Program Discussion Paper Series (2020).Abstract
Economists have long argued that a carbon tax is a cost effective way to reduce greenhouse gas emissions. Increasingly, members of Congress agree. In 2019, seven carbon tax bills were filed in Congress (Kaufman et al., 2019). In addition, the Climate Leadership Council has built bipartisan support for a carbon tax and dividend plan (Baker et al., 2017). In contrast, the Trump Administration is retreating from any climate policy and has taken steps to withdraw from the Paris Accord, citing heavy economic costs to the U.S. economy from meeting the U.S. commitments made during the Obama Administration. In his June 1, 2017 statement on the Accord, for example, the President claimed that the cost to the economy would be “close to \$3 trillion in lost GDP and 6.5 million industrial jobs…” (Trump, 2017). What is the basis for claims about the economic impact of a carbon tax? Economic impacts of a carbon tax typically are estimated using computable general equilibrium (CGE) models (as was done for the report on which Trump based his claims). These models, while helpful, make many simplifying assumptions to remain tractable, including optimization, representative agents, and simplified expectations and dynamics, so at a minimum those estimates would ideally be complemented by empirical evidence on the macroeconomic effects of carbon taxes in practice. With carbon taxes in place in twenty-five countries around the world, including some dating to the early 1990s, empirical analysis of historical experience is now possible. This paper considers carbon taxes in Europe to estimate their impact on GDP and employment.
dp_86_metcalf_stock.pdf
2015
Metcalf, Gilbert, and James H Stock. “The Role of Integrated Assessment Models in Climate Policy: A User’s Guide and Assessment.” Cambridge, Massachusetts, USA: Harvard Environmental Economics Program, 2015.Abstract

This paper considers the role of integrated assessment models (IAMs) in the construction of climate policy. We focus on questions involving the role of IAMs in estimating the social cost of carbon (SCC), how best to handle the considerable scientific uncertainty underlying the IAMs from the perspective of estimating the SCC, and whether an IAM‐based SCC should be abandoned and replaced by expert judgment or another substitute. The perspective we adopt in tackling these questions is rooted in the specific needs of the existing U.S. institutions responsible for making and implementing climate policy, specifically regulatory agencies within the Executive Branch and Congress should it choose to take up climate legislation. Our discussion has three premises. First, policy makers need a numerical value and an uncertainty range for the SCC for policy evaluation and implementation. Second, whatever the true value of the SCC is, it is not zero. Third, considerable uncertainty surrounds the current state of scientific knowledge about the current and future costs of climate change. The evolving nature of the science and the ultimate goal of informing first‐best policy suggests to us that the official SCC – the SCC used for regulatory analysis by the U.S. Government – should not be thought of as a single number or even a range of numbers, but more broadly as a process that yields updated estimates of those numbers and ranges. Viewed in this way, the ultimate goal of the process is scientific credibility, public acceptance, and political and legal viability.

dp62_metcalf-stock.pdf