Deadly heat waves are becoming more frequent in California

Science Daily: From mid July to early August 2006, a heat wave swept through the southwestern United States. Temperature records were broken at many locations and unusually high humidity levels for this typically arid region led to the deaths of more than 600 people, 25,000 cattle and 70,000 poultry in California alone.

An analysis of this extreme episode carried out by researchers at Scripps Institution of Oceanography, UC San Diego, put this heat wave in the context of six decades of observed heat waves. Their results suggest that such regional extremes are becoming more and more likely as climate change trends continue.

The team, led by climate scientist Alexander Gershunov, examined meteorological conditions that lead to this and other recorded heat waves, when temperatures rose into the hottest one percent of historical summertime daily and nightly temperatures recorded in California and Nevada since 1948. The scientists found that heat waves in the region often fall into either of two types: the typical "daytime" events characterized by dry daytime heat and rejuvenating nighttime cooling, or the less typical "nighttime" heat waves characterized additionally by high humidity and hot muggy days and nights.

Since the early 1990s, nighttime heat wave events in California, which historically had been less common, have become more prevalent, increasing in both frequency and intensity. The pinnacle of nighttime heat waves occurred in a 17-day episode during July 2006 when a persistent warm pattern was aggravated by unusually humid conditions, associated with warm ocean waters off Baja California, Mexico....

A shack in California's Mojave Desert, shot by Abramandis, Wikimedia Commons, under the Creative Commons Attribution ShareAlike 3.0 License