Heat Waves Getting Worse »

Heat waves out West are getting worse as the climate changes, a new study finds.

One example: 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 were recorded.

The event included extreme muggy heat that is part of a trend of increasing nighttime heat wave activity observed over the last six decades, the researchers said in a statement today. This trend has accelerated since the 1980s and has become especially prevalent in this decade, they conclude.

The results are not isolated, and they fit with predictions that a warmer world will produce greater extremes.

A study in 2007 found European heat waves are nearly twice as long as they were a century ago and the number of hot summer days there have tripled.

Why it matters: Other studies show heat waves are deadlier than hurricanes or tornadoes, and they have been so throughout modern history. Climate experts have warned that the sort of serious heat wave that is now possible given current climate conditions, but which has not struck yet, could kill thousands of U.S. residents.

And there's some irony in the problem:

As heat waves worsen, more energy is used to run air conditioners. If the electricity is generated using fossil fuels, this could also mean even more emissions of heat-trapping gases that cause climate change, scientists wrote in the Journal of Applied Meteorology and Climatology last year.

"Electricity demand for industrial and home cooling increases near linearly with temperature," said the leader of that study, Norman Miller, an earth scientist at Lawrence Berkeley National Laboratory and geography professor at the University of California, Berkeley.

"In the future, widespread climate warming across the western U.S. could further strain the electricity grid, making brownouts or even rolling blackouts more frequent," Miller said.

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