IAM Demographic Model

Demographic Model

The Community Demographic Model (CDM), developed by the Integrated Assessment Modeling (IAM) group at the National Center for Atmospheric Research (NCAR) projects population, age, gender, urban versus rural residence, and household type for at least 31 world regions, and the spatial distribution at the grid level. These demographic projections serve as an input to the integrated Population-Economy-Technology-Science (iPETS) model, and can also be used for the broader climate research community to explore the implications of alternative population scenarios for emissions and impacts. 

The CDM consists of four model components:

    • The Urbanization Projections component is based on historical experiences and provides multiple long term scenarios covering wide but plausible range of outcomes of national subnational urbanization levels.
    • The Multiregional Population and Urbanization component uses a multi-state demographic methodology to project changes in population size and age and gender compositions across rural and urban areas that are consistent with the results of urbanization projections.
    • The Household Projection component is based on a household headship method to project the changes of population living in households specified by region, age, household size, and rural/urban residence that are consistent with the results of multiregional population and urbanization projections.
    • The Spatial Population Downscaling component downscales regional population and urbanization projection results to the level of grid-cells. 

Background Information

The earlier version of population, urbanization, and household scenarios developed for use in the 2010 PNAS paper are available below. Documentation for these scenarios can be found in the online supporting information to that paper, as well as in Jiang & O'Neill (2009).

[PNAS 2010 demographic scenarios]

Applications of the Community Demographic Model

CDM model components have been used to develop numerous scenarios and projections:

    • The Urbanization Projection model has been used to develop urbanization scenarios for the Shared Socioeconomic Pathways (SSPs) as described in Jiang & O'Neill (2015) and Jiang (2014). Download the SSPs urbanization projection data set.
    • The Multiregional Population and Urbanization Projection model has been used to produce a new set of projections of rural and urban population by age and gender for 31 global regions that are consistent with NCAR's SSPs urbanization projections and IIASA's SSPs population projections, which will be noted in Jiang & Nawrotzki (forthcoming).
    • To meet the needs of multiregional population projections and other research purposes, the CDM-International Migration Dataset has also been developed to record the age and gender profiles of bilateral international migration flows. See Nawrotzki & Jiang (2014) and Nawrotzki & Jiang (2015).
    • The Spatial Population Downscaling model has been used to generate Special Report on Emissions Scenarios (SRES)-specific spatial rural and urban population distribution for the United States grounded in historical experiences. See Jones & O'Neill (2013). 
    • The Spatial Population Downscaling model has been used to develop spatial population scenarios for the SSPs, as described in Jones and O'Neill (2016).