date, not really abrupt. It would be useful to pay more explicit attention in integrated-assessment economic models to other kinds of potential shocks, perhaps focusing on major changes in water and agriculture systems for the United States as well as to shifts in monsoonal patterns or droughts in other regions. This effort is hampered to date, however, because there are few scenarios for abrupt climate change that have been handed off by geoscientists to the economic modelers.

Attention to climate extremes in the wake of anthropogenic-induced gradual warming has been reported by Easterling et al. (2000). This study examined outputs of general circulation models that show changes in extreme events for future climates under greenhouse warming scenarios, such as increases in high temperatures, decreases in extreme low temperatures, and increases in precipitation events. These authors suggested a range of impacts due to these extremes, including the impacts to natural ecosystems and society.

In summary, climate change inevitably has impacts. Abruptness increases those impacts, especially on unmanaged and long-lived systems. To date, however, relatively little research has addressed the possible costs of abrupt climate change or ways to reduce these costs, both because climatologists have not produced appropriate scenarios and because ecological and economic scientists have not concentrated on abruptness. Ways to address this shortcoming are discussed in the next chapter.