climate change for their modeling. An important reason why there have been so few studies on the impacts of future abrupt climate change is that climate scientists have provided social scientists little to work with; only the cooling events of the Little Ice Age and the Younger Dryas have been extensively analyzed, and the database on these remains inadequate. Complicating the issue is the uncertainty of how probabilities of abrupt climate change will be affected by increasing greenhouse-gas concentrations and by nonclimatic factors, such as trends in land and water use and urbanization.

Many economic models require high-resolution climatic and ecological data as inputs. A useful target of spatial resolution is 1° of latitude by 1° of longitude, annual or seasonal temporal resolution, and temperature and precipitation as a minimum for climatic variables. Up to now, scenarios at this resolution have been prepared only for gradual climate change; to be useful in developing impact analyses and projections, such high-resolution scenarios will be necessary for a variety of scenarios of abrupt climate change.

IMPROVE PALEOCLIMATIC DATA RELATED TO ABRUPT CLIMATE CHANGE

Recommendation 3. The quantity of paleoclimatic data on abrupt change and ecological responses should be enhanced, with special emphasis on:

  • Selected coordinated projects to produce especially robust, multiparameter, high-resolution histories of climate change and ecological response.

  • Better geographic coverage and higher temporal resolution.

  • Additional proxies, including those that focus on water (e.g., droughts, floods, etc.).

  • Multidisciplinary studies of selected abrupt climate changes.

Abrupt climate change is evident in model results and in instrumental records of the climate system, but much of today’s interest in the subject was motivated by the strong evidence in paleoclimatic archives of extreme changes. Proxy records of paleoclimate are central to the subject and will continue to be so for some time.

Available paleoclimate records provide information on many environmental variables, such as temperature, moisture, and wind speed and direc-



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