Third, many variables will be measured with new technologies. Of particular importance is the potential for making use of data from satellites and other forms of remote sensing. In the physical and biological sciences there is some tradition of using remotely sensed data, but it is a novelty to the social sciences. Very little effort has been devoted to developing methodologies that would make such data useful for understanding the human dimensions of global change. Indeed, as we note elsewhere, the social sciences, with the exception of geography, have paid little attention to space as a concept and will have to develop new theory and methodology to accommodate global change phenomena that have a strong spatial component. It is especially important that social scientists become involved in the planning of remote sensing systems and the derived data bases. If social science concerns are not introduced early on, information that could be of great value in better understanding the human dimensions of global change may not be collected and archived in a form that optimizes its utility.
Fourth, much of the data of greatest interest will have to be collected on a regional, international, or global basis. The problems of aggregation from smaller to larger units and of assessing comparability across different local or national measurements will be important. There is considerable experience in dealing with these problems in the fields of economics, demography, and comparative politics. But that experience will have to be translated so as to be useful in measuring the very different variables important to global change.
Fifth, the conceptualization and measurement of many key variables must be interdisciplinary. In most cases sound conceptualization and measurement must span several social science disciplines; in many cases it will involve the physical and biological sciences as well. For example, a land use taxonomy must be sensitive to the biological and physical characteristics of a particular land use, such as species diversity that typically accompanies it, its albedo, and its percolation rate. But the taxonomy must also be sensitive to the economic function of the land use, its political regulation, and its cultural meaning. It may be that several taxonomies are required, but if so they must be coordinated to produce useful data.
Finally, although quality and interpretability is of the utmost importance for research on the human dimensions, attention must also be given to issues of cost-effectiveness. New large-scale data collections are costly enterprises. Just as some research projects would be given priority over others, so too would some variables