The Improved Urbanization Projections of the NCAR Community Demographic Model (CDM)

The urbanization projections, as one important components of the NCAR Community Demographic Model, has been developed to meet the requirement of climate change research communities for understanding the long-term and alternative urbanization trends. The model was used to generate global national urbanization projections for all countries under the Shared Socioeconomic Pathways (SSPs) – the new IPCC socioeconomic scenarios. This paper reports the new development of the CDM-Urbanization Projection Model which improves the previous model and the projection results in two main aspects. First, it makes urbanization projection for a region based on more historical data points of selected reference regions, and the selection of the reference regions is now conducted in a more systematic and holistic way. Second, the model is extended and adopted to project urbanization trends of subnational regions (provinces of China, states of India and the U.S., as examples). We carried out validation analysis through comparing projected urbanization trends in the past decades against observed urbanization records at both national and subnational levels. It shows that the improved model produces reasonable and unbiased projection outcomes, covering a wide range of plausible urbanization paths for the long- and medium-term for countries and subnational regions.