Change Research Act (GCRA) of 1990. This requirement helped develop support for the assessment from representatives of the agencies participating in the U.S. Global Climate Change Research Program (GCRP). Similarly, a clear mandate and a strong authorizing environment were provided when a formal proposal was adopted by the foreign ministers of the eight Arctic countries to establish the ACIA. In this case, the mandate by the foreign ministers of the Arctic countries guaranteed that the assessment had a target audience that was not only receptive but also interested in the outcome (Corell 2006). Lack of a mandate can be considered the most significant pitfall of the GBA (Watson 2006). Although the GBA was established by the United Nations Environment Programme to provide a scientific basis for the Convention on Biological Diversity (CBD), it was never formally authorized by the CBD and as a result encountered a number of barriers that might have otherwise been avoided.

These examples illustrate how an assessment with a clear mandate from decision makers is more likely to be viewed as legitimate and salient, particularly if the mandate specifies the degree to which the assessment should identify and evaluate policy or other response options. In fact, maintaining legitimacy requires an assessment to respect the boundary between science and policy, which means that it is to provide policy-relevant information and not to exceed its mandate by providing policy-prescriptive recommendations unless clearly asked to do so.

The state of the relevant scientific knowledge and the decision-making context that an assessment seeks to inform affects the kinds of decisions to which it is relevant, which in turn should help define the appropriate goals and objectives of an assessment. For example, the goal may be to establish the state of knowledge, to indicate the latest understanding of impacts, or to provide response options. For the last, the goal might be to provide information on the effects of alternative response strategies on relevant impact categories. Different goals will have profound implications for the decisions undertaken during the course of an assessment. Confusion on the part of participants regarding the goals of the assessment can severely limit its effectiveness. Assessment participants must come to a mutual understanding of what they are being asked to do in response to the charge.

As part of the mandate, goals and objectives need to be well articulated, including the kinds of decisions that the assessment should inform, how the assessment will be implemented, and how progress toward goals will be measured (NRC 2005). In particular, in the scoping phase of the assessment, organizers need to identify the target audience and the decisions it is intended to inform as well as the types of information needed to make