An intermediate case is that in which people make anticipatory responses based on the experiences of others with similar environmental changes.

Systems of distinctions regarding human interventions with respect to hazard are, of course, somewhat arbitrary. As noted by Hohenemser et al., (1985), much finer distinctions are possible than those offered here. Our distinctions are offered as a nearly minimal set for studying the human dimensions of global change. They reflect current usage in the global change research community (for instance, researchers tend to use the term mitigation to refer to interventions in the human causes of global change but not to interventions in the consequences), and they emphasize the importance of feedbacks between human responses and human causes of global change.

Although the policy debate is usually phrased in terms of global warming, the greenhouse gas emissions that are at the center of the debate do much more to climate than raise the earth's average temperature. In fact, some of the other effects, such as on patterns of precipitation, frequency of major storms, cloud cover, and frequency of extreme-temperature events, may be much more significant in terms of human consequences than changes in average temperature. When we refer to global warming, the reader should understand the whole collection of climatic changes associated with the greenhouse effect.

A somewhat different distinction between adaptation and adjustment is sometimes found in the literature and is particularly useful for policy analysis. Adjustment is defined as what any affected system does after it feels the effect of an environmental change; adaptations are actions taken deliberately, before the environmental effect is felt, to make adjustment less difficult, costly, disruptive, or painful. This distinction separates a class of policies (adaptation) from the effects of those policies on people or natural systems (their adjustments). Sometimes, the term adjustment is restricted to what affected systems would do in the absence of policies of adaptation, as part of assessments of the benefits of those policies. In terms of the distinctions in this report, blocking, improved adjustment, and improvements in robustness may all be the aims of policies on the response side of global change.

The literature on responses to natural hazards distinguishes between adjustments, short-term activities such as warnings or evacuations, and adaptations, long-term social changes that would lower the cost of a recurrence of a hazard. Some of what that literature considers adaptations are treated here as type H mitigations or interventions to increase robustness. Nevertheless, the natural hazard literature includes a more differentiated typology of adjustments than is presented here, including avoiding the loss (e.g., migration), sharing the loss (e.g., relief assistance,