By Daniel Reifsnyder, U.S. Department of State

Having spent the past decade on the negotiating front, I can say with confidence that nations are passionately interested in their vulnerability to climate change and in their options for adaptation. This passion runs highest among the developing countries -- many have contributed (and will contribute) little to the build-up in atmospheric concentrations of greenhouse gases, but they know they may suffer. They worry too that they won't have the resources to adapt.

Why is the U.S. National Assessment so important? Because it is the most comprehensive such effort ever undertaken, because it may serve as a model for other countries, and because it will be a major contribution by the United States to the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), scheduled for completion in 2001.

Arguably the most significant article of the U.N. Framework Convention on Climate Change, and its most lasting achievement, is Article 2. That article contains the Convention's ultimate objective: to achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous human interference with the climate system. The objective also provides that such a level should be achieved in a timeframe sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in an equitable manner.

Even before the negotiations that led to the Kyoto Protocol, there was strong interest in what this level should be. In October 1994, the IPCC held a workshop in Fortaleza, Brazil, to discuss the objective's scientific and technical aspects. As IPCC Chair Bert Bolin said at the time, "It is not an IPCC task to define how terms such as 'dangerous,' 'threaten,' and so on are interpreted. Still scientific information is of basic importance to resolve issues of this kind. When the word 'level' is mentioned, we should present several alternatives, describe the differences, and thereby illustrate the sensitivity. When adaptation is at stake, we need to present information that permits an analysis of what is critical for determination of 'rates of change.' "

Coming to grips with the objective of the Convention will be the most critical and most difficult task for the foreseeable future. Therein lie all the concerns about preserving our environment while maintaining economic prosperity. To date, it has not been possible to say with certainty what climate change may be avoided by stabilizing atmospheric concentrations at a particular level. Even more important, it has not been possible to say precisely how life as we know it would be affected if we attain or avoid a particular level. Much depends on the 'rates of change' Professor Bolin mentioned. But if science can assess these consequences and present them clearly, the task persuading people to act will be much easier.

The IPCC is now fully engaged in preparing its Third Assessment Report. The United States is well placed to contribute significantly to that effort. In addition to legions of U.S. scientists giving freely of their time to serve as lead authors and reviewers, Dr. Robert Watson chairs the IPCC, and Dr. James McCarthy co-chairs its Working Group II on Impacts and Adaptation.

U.S. interest in Working Group II was not fortuitous. Many in the USGCRP recognized that holding this position internationally would complement the enormous domestic effort we are undertaking in the U.S. National Assessment. By assessing the potential consequences of climate variability and change in the organized, methodical manner in which the National Assessment is being undertaken, words such as "dangerous" and "threaten" may come more clearly into focus.

In Fortaleza, Professor Bolin asked, "How can we present scientific information in a way that is relevant for policy-makers?" He suggested that this could be done by:

• Elaborating and explaining the types, sources and consequences of uncertainties.
• Pointing out the role of natural climate variability, in interaction with limited knowledge, in contributing to uncertainties.
• Highlighting the importance of extreme events when assessing damages (and not simply changes in mean conditions).
• Underscoring the importance of extreme, unexpected events in heightening peoples' awareness, in social change, and in human responses.
• Developing improved definitions of critical 'loads,' 'levels,' or 'changes'.
• Improving our understanding of 'irreversibility,' and the processes and time scales needed for restoration of ecosystems.

The importance of scientific assessment to the policy debate cannot be over-estimated. It was the IPCC First Assessment Report in 1990 that led to the Convention. It was the IPCC Second Assessment Report in 1995 that led to the Kyoto Protocol. In Buenos Aires last November, several nations, including the United States, sought to link further reviews of the "adequacy" of commitments to the scientific assessment cycle of the IPCC. Scientific assessment will continue to drive the negotiations, as it has consistently over the past decade. Let me assure those involved in the U.S. National Assessment, you are most assuredly not working in a vacuum. We in the policy community welcome and applaud your efforts.