Robert Stavins has performed a great and valuable public service by his role in moving cap-and-trade from an academic idea to real-world policy. Since the 1980s Stavins has tirelessly promoted the idea that the nation could have cleaner air at less cost if national policymakers would establish gradually shrinking emissions caps on pollutants and allow emitters to make their own decisions about how to adjust to this change in their market environment. Stavins' recent article Addressing Climate Change With a Comprehensive U.S. Cap-and-Trade System 1 makes the case for cap-andtrade as the means to address global warming.

Having spent a great deal of my professional time in the 1980s working to shape a cap-and-trade program to control acid rain and convince Congress to adopt it, I agree with much of Stavins' argument. I take issue only where it seems to me that Stavins stakes too grand a claim for cap-and-trade as a response to global warming.