Heatwaves to move toward coasts, study finds

Aug 29, 2012

(Phys.org)—A new study by researchers at Scripps Institution of Oceanography, UC San Diego, suggests that the nature of California heatwaves is changing due to global warming.

Alexander Gershunov and Kristen Guirguis detected a trend toward more humid that are expressed very strongly in elevated nighttime temperatures, a trend consistent with projections. Moreover, relative to local warming, the mid-summer heatwaves are getting stronger in generally cooler coastal areas. This carries implications for the millions of Californians living near the ocean whose everyday lives are acclimated to moderate temperatures.

"Heatwaves are stressful rare extremes defined relative to ," said Gershunov. "We've known for a while that humid heatwaves that are particularly hot at night are on the rise in California as the warms. Here, we sharpen the geographic focus to consider sub-regions of the state."

Gershunov added that in this new sharper and "non-stationary" perspective, coastal heatwaves express much more intensely than those inland where the summertime mean warming is stronger. This translates to a variety of impacts on the typically cool, un-acclimated coast.

Classic California heatwaves have been characterized as interior desert and valley events that are hot during the day and marked by dryness and strong nighttime cooling. Gershunov and Guirguis said their analysis of observations and data indicates that the emerging flavor of heatwaves marked by greater humidity, greater expression in nighttime temperatures, and greater expression in coastal areas relative to the generally cooler coast are intensifying and will keep intensifying in coming decades. Both coastal and desert heatwaves will continue to be more common as climate changes relative to the past, but the desert heatwaves are becoming less intense relative to strong average warming observed and projected for the interior of the state.

The study, "California heat waves in the present and future," will appear in the American Geophysical Union journal Geophysical Research Letters.

The "non-stationary" approach reflects an acknowledgment by scientists that what has been considered extreme heat is gradually becoming commonplace. The rate of climate warming necessitates a measure of extreme heat relative to the changing average climate rather than to historical climate norms. So, instead of defining heatwaves relative to fixed temperature thresholds, the researchers projected heatwave intensity against a backdrop of increasing average summertime temperature. This causes the definition of heatwaves – temperatures in the warmest 5 percent of summertime conditions – to evolve with the changing climate and reflect extreme conditions relevant to the climate of the time.

"The advantage of using this evolving 'non-stationary' definition is that heatwaves remain extreme events even under much warmer climate," said Gershunov. "If they change in this evolving framework, it's because the variance of temperature is changing, not just the average."

The authors point out that the trend could precipitate a variety of changes in California's coastal communities, where stronger heat will lead to the installation of air conditioners in homes traditionally not in need of cooling.

This lifestyle trend would in turn affect energy demand in , its magnitude and timing. In the absence of technological or physiological acclimatization, high humidity and the lingering of heat through the night is expected to have strong public health implications, placing added stress on many of the more than 21 million who live in coastal counties. The same would be true for animals and plants living in the highly populated and diverse coastal zone.

"This trend has important human health implications for coastal California where most of the state's population lives," said Guirguis. "Coastal communities are acclimated to cooler mean temperatures and are not well prepared for extreme heat either physiologically or technologically through air conditioning use. Populations tend to adapt to changes in their average conditions but extreme events can catch people off guard. An increase in heat wave intensity relative to average conditions could mean much more heat-related illness during heat waves unless effective heat emergency plans are implemented."

Explore further: Trade winds ventilate the tropical oceans

More information: dx.doi.org/10.1029/2012GL052979

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User comments : 12

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Sanescience
1 / 5 (2) Aug 29, 2012
So, in the past I've commented on the challenges of modeling climate with computer models, so here is an article with a link for the "Computer Model". Sadly it had nothing to do with the computer model referenced.

As serious modeling of convection and clouds is a fairly recent thing for climate models, I wanted to see if any changes had been made based on physical model testing that disagrees with past model assumptions about cloud formation.

One such example being this: http://www.econom...21526788
NotParker
1 / 5 (10) Aug 29, 2012
"elevated nighttime temperatures" = urban heat island

Even the EPA knows that!

"Air temperatures in cities, particularly after sunset, can be as much as 22°F (12°C) warmer than the air in neighboring, less developed regions.2

Elevated temperatures from urban heat islands, particularly during the summer, can affect a community's environment and quality of life. While some impacts may be beneficial, such as lengthening the plant-growing season, the majority of them are negative."

http://www.epa.go...ndex.htm

It has NOTHING to do with climate change. Quit moving to cities!
kochevnik
5 / 5 (2) Aug 29, 2012
@NotSmarter "elevated nighttime temperatures" = urban heat island
Even the EPA knows that!
Coastal California cities are cooled by incoming ocean air at night, and do not substantially undergo the heat island process you retard.

2/3 of California coast is a desert. Deserts are not known for their humidity. Until now.
NotParker
1 / 5 (5) Aug 29, 2012
Coastal California cities are cooled by incoming ocean air at night, and do not substantially undergo the heat island process you retard.

2/3 of California coast is a desert. Deserts are not known for their humidity. Until now.


"In the 1930's, the area now referred to as Los Angeles was nothing like it is today. It was covered by irrigated orchards with a high temperature of around 97 °F (The Heat Island Group, 2005). However, as urbanization and industrialization began and vegetation and trees were replaced with concrete and metal, the average temperature of Los Angeles increased steadily (Figure 7) (The Heat Island Group, 2005). The average temperature reached 105 °F and higher in the 1990's "

"As a consequence of replacing vegetation with dark colored surfaces, city temperatures are estimated by scientists to be 2° F-10° F higher than the surrounding environment. "

http://www.enviro...ands.htm
NotParker
1 / 5 (3) Aug 29, 2012

2/3 of California coast is a desert.


Not according to rainfall maps.

http://tchester.o...fall.gif

"A common definition distinguishes between true deserts, which receive less than 250 millimetres (10 in) of average annual precipitation, and semideserts or steppes, which receive between 250 millimetres (10 in) and 400 to 500 millimetres (16 to 20 in)."
kochevnik
5 / 5 (1) Aug 29, 2012
Not according to rainfall maps.
You've never been in California apparently. People travel inland and DIE of thirst and heat. The area has experienced a thirty year drought in which time the desert has expanded. Brush fires are diminishing because there is no longer enough rain to GROW the brush now. If you were out there you would die too. Google would not save you.

Now in Moscow we also have fires like California did. The climate has changed since Soviet times, when everything was always green. In face Moscow used to be a swamp. That's how much conditions have changed
Sanescience
1 / 5 (1) Aug 30, 2012
I'm kind of curious what element people disagree with my statement. I find it interesting that whenever I talk about climate software shortfalls, a lot of people get edgy. Remember, science is about *assuming* your model is incorrect or incomplete in some way and you should continue to test against the real thing to verify and refine your understanding.
wealthychef
not rated yet Aug 30, 2012
So, in the past I've commented on the challenges of modeling climate with computer models, so here is an article with a link for the "Computer Model". Sadly it had nothing to do with the computer model referenced.

As serious modeling of convection and clouds is a fairly recent thing for climate models, I wanted to see if any changes had been made based on physical model testing that disagrees with past model assumptions about cloud formation.

One such example being this: http://www.econom...21526788

When you talk about convection and cloud formation, aren't you talking about weather and not climate?
rubberman
5 / 5 (1) Aug 30, 2012
"When you talk about convection and cloud formation, aren't you talking about weather and not climate?"

Generally yes, unless you are talking about climate drivers such as the position of the jet stream, El Nino or long lasting blocking highs with a pattern of repetition. All things which influence cloud formation on annual/decadal time frames based on their location and duration. I believe this is what Sane is referring to regarding the models.
BikeToAustralia
3 / 5 (2) Aug 30, 2012
Sanescience; dead on. The rest of you; too much grease on your egos leads to hairy palms.

Does this phenomena (winds coming inland no longer cooling as much) hold true with other coastlines worldwide?

We of the USA only pay attention to what directly affects the USA. It disturbs me that quantum entanglement, chaos theory, 'we are all brothers' and 'each part affects the whole' are not an integral part of our every day outlook on life (weltanschauung is a great word). Everything is related to everything else, not just humans and not just 'our people'.
Sanescience
1 / 5 (1) Aug 30, 2012
BikeToAustralia: Well, there is one person probably with a bunch of names like zz5555, vendicular, rubberman, who disagrees and makes a game of the ranking system with personas but wont articulate their position.

*shrug*
rubberman
not rated yet Aug 30, 2012
BikeToAustralia: Well, there is one person probably with a bunch of names like zz5555, vendicular, rubberman, who disagrees and makes a game of the ranking system with personas but wont articulate their position.

*shrug*


Funny, I agreed with you on this one, articulated my position, and can't actually rank because as soon as I click on any star I get kicked back out to the main page and the ranking doesn't go through. But Oh well.... *shrug* indeed.

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