As global warming continues such heat waves will be increasingly common in the future, a Stanford University study concludes.
"In the next 30 years, we could see an increase in heat waves like the one now occurring in the eastern United States or the kind that swept across Europe in 2003 that caused tens of thousands of fatalities," Noah Diffenbaugh, an assistant professor of environmental Earth system science at Stanford, said in a statement.
Diffenbaugh and Moetasim Ashfaq, a former Stanford postdoctoral fellow now at the Oak Ridge National Laboratory, used a series of computer models of climate to calculate changes in the future with increased levels of carbon dioxide and other gases in the atmosphere. Their findings are reported in the journal Geophysical Research Letters.
They calculate that within 30 years average temperature could be 3.6 degrees Fahrenheit, or 2 Celsius, higher than in the mid-1800s.
That level of increase has been reported by others and most atmospheric scientists expect it to lead to warming and a change in a variety of weather and climate conditions.
Diffenbaugh and Ashfaq focus specifically on heat waves over the United States.
They reported that an intense heat wave equal to the longest on record from 1951 to 1999 is likely to occur as many as five times between 2020 and 2029 over areas of the western and central United States.
In addition, they said the 2030s are projected to be even hotter.
"Occurrence of the longest historical heat wave further intensifies in the 2030-2039 period, including greater than five occurrences per decade over much of the western U.S. and greater than three exceedences per decade over much of the eastern U.S.," the researchers reported.
"I did not expect to see anything this large within the next three decades. This was definitely a surprise," Diffenbaugh said.
The research was funded by the Energy Department and the National Science Foundation. The climate model simulations were generated and analyzed at Purdue University.
RANDOLPH E. SCHMID, AP Science Writer