Abstract

Scenarios are quantitative and narrative descriptions of plausible future conditions that provide assumptions for analyses of potential impacts and responses to climate change. Scenarios are ways to help understand what future conditions might be, with each scenario an example of what might happen under different assumptions. Scenarios are not predictions or forecasts, and no probabilities are associated with them. Instead, they provide a range of future conditions to bound uncertainty. The scenarios here include climate, sea level change, land use, and socioeconomic conditions. They are based on peer-reviewed, published sources including materials prepared by the Intergovernmental Panel on Climate Change (IPCC).

Scenarios for the National Climate Assessment include information on:

Climate – plausible representations of future climate conditions (temperature, precipitation, and other variables) produced using a variety of techniques including mathematical models and downscaling methods.

Sea Level – estimates of future increase in global average sea level resulting from climate-related processes such as thermal expansion of the oceans and melting of grounded ice sheets as well as descriptions of selected regional and local anomalies from the global trend resulting from land subsidence or uplift and other factors.

Land Cover, Land Use, and Socioeconomic Factors – projections of the extent and distribution of different categories of land uses such as agriculture, forestry, and settlement, as well as different vegetative covers resulting from human management, climate change, and other factors. Socioeconomic factors include assumptions about potential future demographic, economic, institutional, and other characteristics resulting from different patterns of economic growth and social change.

Materials on Participatory Scenario Planning – a short description of the use of scenarios to consider the implications of uncertain future climate and socioeconomic conditions in planning and decision making. Additional materials are under development and will be released when available.

Links on the right panel provide access to further information about many of these scenario components. Other useful links can be found on the menu at the left side of the page. Frequently Asked Questions (FAQs) are available here for the climate scenarios, and the sea level scenarios, including more information about their development and guidance for use. The IPCC Technical Guidelines are an additional reference on the use of scenarios.

Background for the Scenarios
The U.S. Global Change Research Program (USGCRP) is mandated by Congress to produce a periodic assessment that summarizes the state of knowledge about climate and global change, potential impacts on the U.S., and response options. The National Climate Assessment Development and Advisory Committee (NCADAC) , a Federal advisory committee responsible for producing the report, adopted a scenario strategy prepared by a Scenarios Working Group.