this is an important book on an important subject. Joseph Aldy and Robert Stavins are to be commended for bringing together, under the auspices of the Harvard Environmental Economics Program, such a distinguished group to think through critical aspects of one of the most important policy problems the world faces.

Many public policy problems are at their root political. In these cases, it is reasonably clear what should be done; the challenge is to get the parties to agree on a plan of action, given the complex political constraints they face. Opinions will differ, but I would place the Israeli–Palestinian conflict, US social security reform, and the completion of the Doha Trade Round in this category. Other problems, such as the repair of the American health-care system or how to address radical Islamic terrorism, are more profound in the sense of needing conceptual work on what the right approach is before it is realistic to aspire to political consensus. Global climate change falls within this latter set of problems, so I think it is particularly appropriate that an institution like Harvard devote its formidable intellectual resources to creative thinking about possible solutions.

As an economist who has served in government, I am particularly pleased to see this volume's emphasis on what might be called policy engineering – the development and implementation of new frameworks to address pressing problems.