Second are things whose values are not well captured in markets. Genetic resources are generally undervalued because there are few property rights in genetic resources and people therefore cannot capture the benefits of the investments they might make in preserving biodiversity. Many species are unlikely ever to have marketable attributes, and it is virtually impossible to predict which ones may ultimately have economic value. These consequences are not well identified in current accounting systems.
Third are items that some people value for reasons that have little to do with their ''usefulness" or economic worth. This "ecocentric" valuation assigns intrinsic value to the living world. Species loss, in this view, is undesirable regardless of any economic value that may derive from those species. Humanity, it is held, should not do things that alter the course of natural evolution.
The panel recognizes the difficulty of measuring these noneconomic criteria in the quantitative method described above. Since such values are codified, to some extent, in laws (e.g., those to protect biodiversity), potential greenhouse warming responses must be consistent with protection of the noneconomic values. These may be among the most difficult values to accommodate if climates change substantially. In spite of the difficulties outlined above, the panel believes this cost-effectiveness approach is the most useful method for evaluating policies involving response to greenhouse warming.
Once policy options have been ranked, certain factors not directly related to greenhouse warming come into play in the decision-making process.
One such factor concerns risk perception. People differ in their willingness to take risks. We can expect people to differ in their reaction to the potential and uncertain threat of greenhouse warming as well. Some people may be distressed by the possibility that cherished parts of their cultural heritage or natural landscapes might be lost. Others might be unwilling to accept some aspects of proposed adjustmentsperhaps abandoning their traditional homeland and moving elsewhere. In any case, people and organizations will differ in their judgments about how much society should pay to reduce the chance of uncertain climate change.
Another factor is the constraint of limited resources. The United States is a large, wealthy country. Many other nations are severely constrained in their ability to act because of limited financial and human resources.