Heat Wave Weather Patterns Becoming More Likely

June 25, 2015

New study out from Stanford on the increased frequency of weather patterns associated with extreme heat.  I interviewed one of the authors, Dr. Noah Diffenbaugh in April, and we touched on this in a broader discussion of the California drought – above.

Associated Press:

A team of climate scientists at Stanford University looked at weather patterns since 1979 and found changes in frequency and strength in parts of the world, according to a study published in the journal Nature on Wednesday. These are the types of weather patterns with stationary high and low pressure systems that you see on weather forecasts, which is different than gradual warming from man-made climate change.

The team studied the kind of upper air patterns that “sort of amplifies the warming trend,” said study lead author Daniel Horton.

The study doesn’t attempt to explain why these changes are happening. But in general they fit a theory that has gained momentum in climate science that says melting sea ice in the Arctic has sometimes altered the way the jet stream flows, contributing to extreme weather like Superstorm Sandy, outside experts said.

In many cases, including the eastern U.S. and western Asia in summer, some of these changes have become even more noticeable since 1990, the same period in which Arctic sea ice has gone through a rapid decline, the study found.

For example, the type of summer weather pattern with a northeastern North American high pressure system that keeps it hotter than normal in the eastern U.S. used to happen about 18 days a summer in the early 1980s. It now occurs about 26 days a summer, the study found.

“There are more of them each summer and on average they are lasting longer and the longest are lasting longer,” Horton said.

That pattern shift is even stronger in the summer in Europe and western Asia, Horton and co-author Noah Diffenbaugh found.

The patterns Horton and Diffenbaugh studied are different from the one responsible for the current southeastern U.S. heatwave, Horton said. But the weather patterns were the type responsible for heatwaves that killed more than 50,000 people in western Russia in 2010 and more than 70,000 people Europe in 2003, the study said.

Christian Science Monitor:

Long-awaited rains can’t come soon enough for the 20 million residents of Karachi, where a scorching four-day heat wave has killed at least 800 people.

While acknowledging that periods of extreme heat were not uncommon, Farooq Dar of the Pakistan Meteorological Department told Time that the current heat wave was “unprecedented.”

“It has never been this bad,” he said.

Pakistan’s Prime Minister Nawaz Sharif declared a state of emergency on Tuesday as temperatures rose to over 110 degrees F. (43 degrees C.). The government of Sindh Province, which includes Karachi, later declared a public holiday to encourage people to stay indoors out of the sun, according to the Pakistani newspaper Dawn.


KARACHI, Pakistan — The death toll reached 1,000 on Thursday in the southern Pakistani port city of Karachi as residents grappled with a devastating heat wave that has crippled life and overwhelmed the health care system.

Searing temperatures, which have been as high as 113 degrees Fahrenheit, or 45 degrees Celsius, fell below 100 on Thursday, but a sense of panic and crisis persisted in the city, the country’s financial and commercial capital as well as the capital of Sindh Province.

There has been a sharp increase in the sale of air-conditioners and room coolers, local traders said. Morgues have run short of space, and hospitals are filled to capacity as patients scramble to get treatment for dehydration and heatstroke.

The heat wave has sent over 14,000 people into government and private hospitals across Karachi, with more than 8,000 visiting Jinnah Postgraduate Medical Center, the largest such site here.


But for the time being, Karachi boils. Angry mobs protesting the power outages and having no water blockaded several roads, burning tires. Police official Aslam Khan said there was no violence, though he called it an “anarchy-like situation” in some neighborhoods.

Karachi’s residents tried to find running water to cool off at public taps or broken pipes. Some bathed with their clothes on, while others washed their hands, faces and heads. As power outages rolled across the city, women and children walked down roads looking for shelter after leaving their small, suffocatingly hot homes.

Some expressed shock at how bad it had gotten.

“It seems as if there’s no government,” said businessman Salamat Hussain.

Here, more Diffenbaugh:


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