• Specifying the ways in which population, technology, affluence, preferences, policies, and other forces interact to change the rates of environmentally significant consumption in high-consuming developed economies and particularly in developing economies, where large increases in consumption are anticipated.

  • Identifying and quantifying important sources of variation in the adoption of environmentally beneficial technology among firms within industries.

What Are the Human Consequences of Global Environmental Change?

Human dimensions research has made important progress in understanding the consequences of global change for people and ecosystems. Drawing on earlier research in applied climatology and natural hazards, the past 10 years have seen a major effort to understand the potential impacts of climate change on human activity, as well as studies of the impacts of past and present climate variability, the impacts of ozone depletion on human health, and the effects of land degradation and biodiversity loss on society. Credible climate impact assessments are a basis for developing policy responses to global climate change and for successful application of information on current climate variability to resource management.

Consequences of Future Climate Changes

The first studies of potential global warming impacts analyzed how crop yields and water resources would change in developed countries in response to climate scenarios of monthly changes in temperature and precipitation, based on coarse and uncertain output from climate models simulating the equilibrium response to a doubling of carbon dioxide levels in the atmosphere.62 Later crop modeling efforts have incorporated the direct physiological effects of higher carbon dioxide levels, employed transient climate scenarios and daily data, covered developing countries, and replaced the concept of the unresponsive farmer with that of people capable of flexible adaptation to climate change.63

It appears that many U.S. farmers will be able to adapt to the climate changes expected from a doubling of atmospheric carbon dioxide levels by shifts in technology and crop mix but that others, especially in developing countries, will experience lower yields because they cannot afford technology and may be farming more biophysically vulnerable land.64 Some studies of economy-wide impacts arrive at similar conclusions; 65 however, these conclusions may be sensitive to some of the assumptions underlying the analyses, as discussed in more detail in the section below on integrated assessment.

A major conceptual advance occurred in moving from impact assessments based on climate model scenarios to analyses based on an understanding of vulnerability.66 The lack of consensus about how climate may change at the



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