Urban Expansion 2050

Across the five Shared Socioeconomic Pathways (SSPs), global urban land is projected to grow by 0.6–1.3 million km² between 2015 and 2050, an increase of 78%–171% over the 2015 urban footprint. More than two-thirds of this new urban land is expected in Asia (46%–49%) and Africa (16%–25%), and more than 70% of it falls in the humid temperate and tropical climate zones.

This expansion intensifies urban heat islands. It raises average summer daytime and nighttime air temperatures by 0.5–0.7 °C, and by up to about 3 °C in some locations. On average, this expansion-induced warming is about half as strong as the warming projected from greenhouse gas emissions under RCP 4.5, and in some places up to twice as strong.

The land projections come from URBANMOD-ZIPF, a global urban land change model that preserves Zipf’s law of urban cluster sizes. The model first relates urban land per capita to GDP per capita to estimate how much urban land each region needs under each SSP, then allocates new urban land at 5 km resolution using slope, distance to roads, population density, and land cover.

Heat island intensification is estimated with sigmoid models that link urban cluster size to satellite (MODIS) land surface temperature. These models are fitted separately for arid, tropical, temperate, and cold climates and then translated into changes in air temperature.

This additional warming increases extreme heat risk for about half of the future urban population, primarily in the tropical Global South, where existing forecasts already indicate stronger greenhouse gas–driven warming and adaptive capacity is limited. Medium-sized urban clusters (roughly 100–5,000 km²) experience the strongest warming. Because both expansion and expansion-induced warming remain substantial even under the sustainability pathway (SSP1), the study concludes that policies to restrict or redistribute urban expansion, together with planning strategies that mitigate urban heat, are needed in the most vulnerable urban areas.

The Earth Engine app above lets you explore the projected urban land expansion, and the underlying data are openly available on WRI Resource Watch. A follow-up study, “Persistent increases in nighttime heat stress from urban expansion despite heat island mitigation” (Journal of Geophysical Research: Atmospheres, 2021), uses regional climate simulations to show that about half of the nighttime heat stress increase from urban expansion persists even after large-scale deployment of cool roofs.