Equity dimensions of future vulnerabilities to climate hazards: Long-term spatial population projections for New York City consistent with Shared Socioeconomic Pathways

Projections of future population are important for a myriad of reasons. Large cities, states, and countries routinely produce near- and mid-range population projections. In the context of climate change, the Shared Socioeconomic Pathways (SSP) framework is used at global and national scales to project long-term population to inform future emissions scenarios and understand future climate-related exposures and impacts. Much less consideration has been given to long-term projections at smaller scales, even though climate impacts are place based and cities now host most of the world's population. Cities and their metropolitan regions are complex, heterogeneous in terms of population, environmental, and built features. Thus, using global or national-scale approaches overlooks important aspects of urban futures. Cities are diverse, fluid population centers home to migrants, with employment opportunities yet substantial inequality. These quintessential city-centric features are ignored in global/national-scale population projection methods, including long-term ones consistent with the SSPs. Leveraging state-level SSP-based projections, here we extend that approach for New York City, currently home to 8.8 million persons. Combining multistate and multiregional demographic projection and spatial downscaling models, we project county-level population by racial/ethnic groups and age-sex to 2100 and downscale to 100 m. Such projections allow for an equity lens to inform assessments of future vulnerabilities to climate hazards. Four of the five SSPs project that the population of New York City will be smaller and much older at the end of the century, though these futures are dependent on demographic assumptions about fertility and especially migration.