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Urbanization Drives Southern California Heat Waves – NASA News
Summer 2008 in Southern California goes down in the books as cooler than normal. The thermometer in downtown Los Angeles topped 90 degrees Fahrenheit (32.2 degrees Celsius) just once in July, August and the first two-thirds of September. But don’t expect this summer’s respite from the usual blistering heat to continue in the years to come, cautions a group of NASA and university scientists: The long-term forecast calls for increased numbers of scorching days and longer, more frequent heat waves.
So what’s behind this long-term warming trend? Patzert says global warming due to increasing greenhouse gases is responsible for some of the overall heating observed in Los Angeles and the rest of California. Most of the increase in heat days and length of heat waves, however, is due to a phenomenon called the “urban heat island effect.”
Heat island-induced heat waves are a growing concern for urban and suburban dwellers worldwide. According to the U.S. Environmental Protection Agency, studies around the world have shown that this effect makes urban areas from 2 to 10 degrees Fahrenheit (1 to 6 degrees Celsius) warmer than their surrounding rural areas. Patzert says this effect is steadily warming Southern California, though more modestly than some larger urban areas around the world.
Dramatic urbanization has resulted in an extreme makeover for Southern California, with more homes, lawns, shopping centers, traffic, freeways and agriculture, all absorbing and retaining solar radiation, making our megalopolis warmer,” Patzert said.
These trends may capture the attention of utility companies and public health officials. “We’ll be using more power and water to stay cool,” says study co-author Steve LaDochy of California State University, Los Angeles. “Extreme heat, both day and night, will become more and more dangerous, even deadly.”
The findings are published in the July 2008 issue of the Yearbook of the Association of Pacific Coast Geographers. JPL oceanographer and climate scientist Josh Willis was also a co-author on the research.
NASA JPL: Southern Californians get a cool summer, but a warm future
Heat Waves in Southern California: Are They Becoming More Frequent and Longer Lasting?’
- Journal paper (PDF)