Population Growth Can Warm a City As Much As Climate Change

Urbanization in California’s Central Valley could raise local temperatures an extra one to two degrees Celcius

Thermal City
Joseph Giacomin/Corbis

Climate change is not doing well by California. But there’s another factor expected to heat up the state's Central Valley—a growing population, and the urban development that goes along with it.

If current trends hold, millions more people will live in the area by 2100, which will mean more buildings and roads to accommodate them. And this infrastructure will trap the sun’s heat and, according to a new study, raise the local temperatures by an extra one to two degrees Celsius during the already hot summer months. That's double the warming expected from climate change.

Pacific Standard reports:

The heating comes from the so-called urban heat island effect, which describes how the dark, metal-and-asphalt materials of a city absorb and trap warmth from the sun. The urban heat island effect makes cities hotter than they would be otherwise, if they weren’t developed. The Central Valley now is highly agricultural, but the United States Environmental Protection Agency predicts that by 2100, a lot of that farmland will have been converted to buildings. [Study author Matei] Georgescu used the EPA's model as a basis for his own calculations for what urban heat island effect Central California will experience in 2100.

There are relatively simple solutions that can help ameliorate the heat island effect—painting rooftops white or planting greenery on them significantly reduces the amount of heat buildings absorb. (A lighter color makes the surface more reflective, and plants remove heat from the air via transpiration.) The Central Valley's currently an agricultural area, and green roofs could also help keep the area’s farming tradition alive as the fields get plowed into concrete. They might even be able to do something about the air quality, too.

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