climate averages and variabilities likely will reach levels not seen in instrumental records or in recent geological history. These trends have the potential to push the climate system through a threshold to a new climatic state. What are the likely impacts of anthropogenic changes in climate on human and ecological systems? What kinds of tools do we have to foresee potential impacts? What steps can societies take to reduce and increase adaptiveness?

To gather information and facilitate discussions on these questions, the committee hosted a workshop on the societal and economic impacts of abrupt climate change. The workshop included scientists grouped roughly into the areas of economics and ecology, although this grouping does not adequately capture the broad range of interests and disciplines of the participants. Initially, it may appear that ecology and economics are disparate and unrelated disciplines—seemingly working more at odds than together—with one apparently concerned only with maximizing short-term profits while the other is apparently concerned with maximizing long-term ecosystem preservation. Yet the workshop revealed similarities in methodologies and interests. Both areas are concerned with highly complex, nonlinear, dynamic systems, in which individual firms, industries, plants, or animals interact to produce strange and surprising outcomes. Both disciplines are concerned with empirical understanding of systems and with preserving valuable entities or systems from ill-designed and often inadvertent human interventions. The committee believes that the interaction between workshop participants from these two disciplines was a valuable contribution to the understanding of how abrupt climate change can affect the natural and human-influenced systems. The workshop highlighted a considerable body of work directly relevant to understanding impacts of abrupt climate change exists in disciplines such as archaeology, sociology, and geography, and identified opportunities for the concept of abrupt climate change to motivate better connections between these diverse fields of study.


Given the focus of this chapter, it is important to understand the term “abrupt climate change” in the context of ecological and economic systems. As defined in Chapter 1, an abrupt climate change occurs when the climate system is forced to cross some threshold, triggering a transition to a new state at a rate determined by the climate system itself and faster than the

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