An Introduction to the Economics of Climate Change Policy

Eileen Claussen, President, Pew Center on Global Climate Change

What are the potential costs of cutting greenhouse gas emissions? Can such reductions be achieved without sacrificing economic growth or the standard of living we have come to enjoy? These are important questions, and they come up again and again as the United States and other nations consider what actions are needed in response to climate change.

Many participants in the climate change debate — in government, industry, academia, and non-governmental organizations — have conducted economic assessments to determine the costs of taking various actions to address climate change, with the number of economic assessments increasing exponentially in recent years. Differences among their quality and predicted cost of action, or inaction, have also grown, making it difficult to have faith in any one analysis.

The primary example of varying model results can be seen among the numerous reports predicting the domestic costs of complying with the Kyoto Protocol. Some have concluded the United States can reduce its emissions significantly below its Kyoto target (7 percent below 1990 levels), with net economic savings. Others have predicted dire effects on the U.S. economy. The truth most likely lies somewhere in-between.

Behind each analysis is an economic model with its own set of assumptions, its own definitions of how the economy works, and its own data sets. Unfortunately, these models often seem to be impenetrable "black boxes" allowing only a select few to decipher and interpret their results.

Fortunately, along with the rise in economic modeling there has also been a focus on identifying the differences among models. Professor John Weyant of Stanford University, the author of this report, has been at the forefront of these efforts as Director of the Energy Modeling Forum of Stanford University (EMF). His EMF working group convenes the world’s leading energy and climate modelers to discuss and model current energy policy topics.

In this report, Professor Weyant identifies the five determinants that together explain the majority of differences in modeling cost estimates. This is great news for those engaged in the climate change policy arena who are consumers of economic modeling results. Five key questions can be raised to help policy-makers understand the projected costs of climate change policy: What level of greenhouse gas emissions are projected under current policies? What climate policies are assumed to be put in place to achieve emissions reductions? What assumptions are made about how advances in technology might affect these emissions? To what extent are environmental impacts of climate change included? And is the full set of choices that firms and consumers have when presented with rising energy prices accounted for?

This paper would not have been possible without the assistance of numerous individuals. The author and the Pew Center would like to thank Ev Ehrlich, Judi Greenwald, Larry Goulder, Henry Jacoby, Rich Richels, Dick Goettle, Bill Nordhaus, and Bob Shackelton for their thoughtful comments on previous drafts of this paper.

We acknowledge the use of material from a background paper prepared by Robert Repetto, Duncan Austin and Gwen Parker at World Resources Institute.