Council Commentary

New Website for Policy-Relevant Population Modeling Essential for Equitable Climate Action

Predicting changes in populations—their size, distribution, movement, and demographics—is becoming a core element of climate research. It is especially vital for understanding issues of equity and justice in relation to our growing climate crisis. That’s why we’re proud to announce the launch of a brand-new website, the Community Demographic Model (CDM). CDM is a product of the Population Council’s initiative on Population, Environmental Risks, and the Climate Crisis (PERCC). The new website is freely available to everyone with an internet connection, giving the global climate science community access to one of the most detailed, complex, dynamic, and policy-relevant population modeling tools in the world.

The CDM is not a set of fixed predictions. Instead, it is a growing platform that can be used to generate an infinite number of fine-grained and geographically specific projections relevant to human-environment dynamics. Its headline features are four models dealing with different aspects of population change, risk, structure, and composition, including variables like age and gender as well as household makeup, urbanization trends, spatial distribution of population, migration status, and many others. By combining with other modeling tools and databases, the CDM can account for changes in almost any set of external variables—such as laws and policies, climate models, and shifts in socio-economic norms.  

The incredible richness and scenario-based flexibility of the CDM’s design allows for multivariable modeling capable of making detailed predictions about the consequences of specific policies or demographic changes during specific time periods. For instance, older adults living alone are at far greater risk during intense heatwaves. The CDM, by incorporating data on age and household structure, can quantify that risk on a region-by-region basis under a series of different scenarios. Or, consider the impact of education as a way to make communities more adaptable to changing climate: the model can be used to weigh those benefits against the increased emissions caused by the resulting economic growth. And with migration a major consideration among climate researchers and policymakers, the CDM again stands out as a tool to predict multi-directional migration down to the level of individual states and provinces, allowing for direct study of climate’s effects on population movement. Some questions can even be handled on the level of neighborhoods in individual cities, differentiated by variables like population density and urban/rural status. 

The models have a storied history. They were developed by Population Council researchers in collaboration with scientists at the US National Center for Atmospheric Research, the International Institute for Applied Systems Analysis, and the US Department of Energy’s Office of Science. They were made consistent with the Shared Socioeconomic Pathways (SSPs), a set of modeling scenarios that have guided international climate research since they were first created. The urbanization module became a core part of the demographic projections used by the Intergovernmental Panel on Climate Change (IPCC), the United Nations organization responsible for the widely used climate assessments globally. The CDM also made significant contributions to work on human-environment systems supported by the US Department of Energy, along with many other research initiatives. In total, the CDM models have already been cited in more than 350 peer-reviewed scientific articles. 

The CDM project is spearheaded by Population Council researchers Leiwen Jiang, who also serves as founding director of the Asian Demographic Research Institute at Shanghai University, and Hamidreza Zoraghein, an expert in human-environment dynamics.  

Jiang and Zoraghein’s current priorities on CDM include assembling fine-grained local datasets to cover additional geographic regions. They are working with Population Council offices in Mexico and Pakistan, for instance, and are actively seeking collaborators who can help with low-data regions that are most vulnerable to the immediate effects of climate change. The team is also expanding the set of demographic variables and developing new ways to use nontraditional sources of demographic data. Where traditional sources like the census are updated only once a decade, demographic and spatial information from satellite imagery, phones, and social media might let researchers analyze migration and population dynamics much more frequently.  

The CDM is a crucial piece of PERCC’s larger efforts to understand how the climate crisis is affecting lives and livelihoods around the world. It is one of the most potent tools to find ways of blunting its effects and improving our ability to adapt to the changing environment. Working with collaborators, we can use CDM to ask questions with extraordinary precision. For instance: in countries with aging populations and rising temperatures, which areas are most at risk for heat-related medical emergencies? Which local policies will help create households with the right combination of education, location, and size to adapt most effectively to climate change? We welcome partnerships to help us identify new questions and develop solutions that can ensure climate equity and well-being for all. 

The CDM website is available here, and we’d love to talk to you about collaboration, demographic data, access to the CDM model code, new initiatives and applications of our work, or other ways to get involved. Reach out to our team at