By Anthony C. Janetos, NAST Co-Chair, NASA Headquarters

The National Assessment process on which we have collectively embarked depends on both outreach to a variety of national and regional stakeholders for the identification of important issues, and on the ability of the scientific community to analyze those issues, and suggest where vulnerabilities and opportunities may lie. In order to make this aspect of the process work, the assessment must have a component that investigates issues that are truly national in their importance, either because of the magnitude of the potential consequences or because the issues transcend regional boundaries.

It is no surprise that the regional workshops initially suggested a large number of issues that have either or both of these characteristics. At the time of last year's Climate Forum, the list of national issues for possible investigation was very long, and the prospects of investigating all of the issues of concern were correspondingly daunting. One of the early challenges of the National Assessment was deciding which of the many possible issues to address from a national perspective in this first round of analysis, so that we could be sure to do a few things really well.

This issue of Acclimations focuses on the sectoral component of the National Assessment. The decision to focus on five national issues: water, agriculture, forests, coastal areas, and health, was taken with the full knowledge that there were many others that might have been interesting and will ultimately also prove to be important. Nevertheless, it was felt that these five provided a critical minimum number to investigate that would illuminate some of the potential consequences of climate variability and change from a national perspective. For each, there is an existing body of scientific literature on which to draw, and strong analytical capabilities within the scientific community. The federal agencies also showed a strong commitment to supporting analytical studies through the end of this first phase of the assessment process. A consensus quickly developed that these five issues, while not a complete story by themselves, would nonetheless present information critical to continue the national debate about what we do and do not know, what options are available for adaptation, and where both vulnerabilities and opportunities may exist in the future.

Although we have used the word "sector" as shorthand, we have not defined these issues from the traditional economic perspective that is implied by that term. Rather, we have encouraged as comprehensive an investigation as possible for each area of interest, from the perspective of the physical and biological sciences, to economics and social sciences, to understanding what coping strategies or opportunities might exist. The analyses will draw on the available scientific literature, but are also expected in most cases to draw on new modeling studies using consistent climate scenarios to investigate the potential responses of the systems of interest. We have also encouraged each team to reach out very broadly into its own research and user community to incorporate their expert insights. Such analyses are intended to go well beyond what has been possible previously, and begin to provide a more integrated national picture of the potential consequences of climate variability and change, albeit a picture with regional texture.