Though current work in integrated assessment (IA) of global environmental change stands on foundations at least twenty years old, the level of interest and attention of the past five years is unique. Moreover, the past two years have shown increasing signs of maturation of the field -the first review articles and conferences, as well as a series of contributions summarizing cumulative results, critiquing current practice, and calling for development of a more connected professional community, with associated communication channels and professional standards.
Two papers in this issue of Climatic Change make significant, though early, contributions, to these attempts to define and advance a discipline of integrated assessment (IA). Granger Morgan and Hadi Dowlatabadi present policy-relevant insights drawn from five years work in the Carnegie-Mellon IA project, and state their priorities for further work. James Risbey et al. add their voices to calls for professional standards, propose a taxonomy of forms of critical criteria, and critique a few systematic pitfalls of current practice.
Morgan and Dowlatabadi summarize a set of contributions that are rich and astonishingly far-ranging, including the following: estimating costs and effects of electric utility demand-side management programs; estimating and valuing impacts of sea-level rise; modeling and valuing changes in terrestrial ecosystems; constructing dynamic indices to compare effects of multiple trace gases; estimating orderof-magnitude costs and effects of geoengineering measures; designing adaptive policies; measuring public knowledge and attitudes toward climate change and the environment; and estimating the effects of a carbon tax. As a separate contribution, they present a checklist of rules of good practice for doing IA. This sensible and wise list, presumably distilled from the experience of their project, charges the integrated assessor to focus on uncertainty; to iterate; not to neglect areas of ignorance; to include values explicitly, preferably parametrically; to assess the issue in broader social context; to span the problem through coordinated multiple analyses, not a single Procrustean model; and to support multiple assessments. This final item presumably addresses not assessors, but the sponsors and users of assessment.
Risbey et al. do not survey the field, but stalk bigger, more dangerous preydefining and applying professional standards for IA. Their paper presents many opportunities for criticism and dissent, but they are above all to be commended for taking on such troubled and important questions. They propose a preliminary critique of IA, through sketching three classes of critical criteria: discipline-based Climatic Change 34: 315-326, 1996. * These images echo Guetzkow's characterization of formal models in social science, as 'bridges between islands of theory' (Guetzkow, 1962).