Heat waves becoming more prominent in urban areas, research reveals
For past four decades, global warming has been amplified in cities, warns UCLA geographer
The frequency of heat waves has increased dramatically over the past 40 years, and the trend appears to be growing faster in urban areas than in less-populated areas around the world, a new study suggests.
“Our findings suggest that urban areas are experiencing a kind of double whammy — a combination of general climatic warming combined with the heat island effect, wherein human activities and the built environment trap heat, preventing cities from cooling down as fast as rural areas,” said Dennis Lettenmaier, a co-author of the study and a UCLA geography professor. “Everything’s warming up, but the effect is amplified in urban areas.”
Lettenmaier and his co-authors studied 217 urban areas across the globe and found that prolonged periods of extreme heat increased significantly in 48 percent of them between 1973 and 2012.
The results, which were published today in the journal Environmental Research Letters, show that about only 2 percent of those urban areas experienced a significant decline in heat waves. And the change was more dramatic at night: Almost two-thirds of the urban areas showed significant increases in the frequency of extremely hot nights.
“The fact that the trend was so much stronger at night underscores the role of the heat island effect in urban areas,” Lettenmaier said. “You have heat being stored in buildings and in asphalt, concrete and other building materials, and they don’t cool down as quickly as they would outside of the urban area. This effect was likely exacerbated by decreasing wind in most of the urban areas.”
The study is one of the first to focus solely on the extent of extreme weather in urban areas globally and to examine disparities between densely populated and less-densely populated areas.
Lettenmaier collaborated with researchers at the Indian Institute of Technology Gandhinagar, Northeastern University and the University of Washington. The team obtained daily observations for rain, air temperature and wind speed from the National Oceanic and Atmospheric Administration. The researchers identified about 650 urban areas with populations greater than 250,000 and then refined the list to the 217 locales based on the areas’ proximity to weather stations with complete weather records and NOAA data — most were located at airports close to urban areas. Although the researchers would have liked to have more data for urban areas in Africa, Lettenmaier said the report provides as close as possible to a representative sample of changing weather conditions in the world’s cities.
For each of the locales in the study, the researchers identified extremes for temperature, precipitation and wind, calculated heat and cold waves, and pinpointed individual extremely hot days and nights.
The study defined heat waves as periods in which the daily maximum temperature was hotter than 99 percent of days for the four-decade period and in which those temperatures were sustained for a consecutive period of six or more days. (The median length of heat waves was eight days.) It found that the average number of heat waves per year increased by over 50 percent during the period.
Of the five years with the largest number of heat waves, four were the most recent years for which data was available: 2009, 2010, 2011 and 2012. Urban areas in South America experienced the greatest increase in frequency of heat waves, followed in order by those in Africa, Europe, India and North America.
Researchers also found other striking examples of climate change within urban settings. Sixty percent experienced a significant decline in extreme windy days, 17 percent experienced a significant increase in daily precipitation extremes, and 10 percent experienced a significant increase in maximum annual precipitation.
“Urban areas make up a relatively small part of the global land area, but over half the world’s populations now live in them, so the trend is troublesome,” said lead author Vimal Mishra, an assistant professor of civil engineering at IIT Gandhinagar. “The combination of higher temperatures and lower wind in particular is not a good combination for human health and well-being. This should concern everyone.”
The increase in precipitation could damage cities’ infrastructure, which could also mean large economic losses, Mishra said.
Using a separate data set of 142 pairs of urban and non-urban areas, the researchers found that the frequency of heat waves grew 56 percent more quickly in urban settings than in surrounding areas that were less populated. Urban areas experienced 60 percent fewer extremely windy days than non-urban areas.
“In urban areas, buildings are disrupting the air flow, which affects not only the immediate area of buildings, but apparently the larger regional wind fields,” Lettenmaier said. “The reduction in wind may well be exacerbating the heat island effect.”
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Just exactly for how long have people headed out of cities for cooler climes during summer months? I’ve been doing it for as long as I remember, but I can’t remember much before my birth in 1958.
The Romans headed for the hills each summer.
What year was that?
The roman Emperors, their families, (and the other rich Roman and Greeks who could afford two houses (er, palaces) did it back before Christ was born. One in the city for its conveniences and access to power and influence and politics, one in the hills during the hot months of the year.
Later, in the 1870’s, the “city club” members who could afford it built “country clubs” out in the country for the same reason. A few in Pittsburgh, for example, bought an old lake and dam upstream of Johnstown PA for their “country club”, and decided to put a “fish trap” across their old dam’s drainage canal … Rains came, and the lake level rose; maintenance bills came but the needed inspections and repairs were not done, and hundreds were killed when the dam broke.
All because of UHI.
But today, the Johnstown tragedy would be blamed on CAGW (or the rich), not on poor maintenance by the rich.
Thanks!
I imagine the St. Francis dam failure, which flooded my great-grandfather’s ranch in Santa Paula in 1928, was also caused by CAGW – which was caused by UHI, etc.
http://en.m.wikipedia.org/wiki/St._Francis_Dam
But in the Nordic countries we head for any place as long as there is a view of the Mediterranean sea. And we do that at all year.
That’s what I would do. In some locations the effect is reversed.
I saw the diary of my grandmother where she did the same though I have an earlier reference to it in days when we would not have even rated London as a big town.
The British in India decamped from the lowlands and headed for the hill stations every summer building railways into the mountains for the purpose. In the USA the good people of Tucson used convict labour to build the road to the top of Mount Lemmon where they built the little town of Summerhaven to escape the heat.
Since cold waves kill more people than heat waves, can we assume that the mortality due to temperature in cities is lower than in rural areas?
The problem is that cold weather brings snow and the effects of removing snow causes a lot of deaths.
http://wattsupwiththat.com/2015/01/13/cold-kills-summer-no-sweat-for-aussies-but-winter-freeze-fatal/
We don’t shovel a lot of snow in Australia, especially places like Brisbane.
Too many confounding factors.
Medical attention is closer in urban environments and there is more social support too.
People look after each other.
“urban environments …People look after each other.”
Hasn’t been my experience, but maybe that’s a Detroit thing?
Absolutely in my experience, to our families lament. My little nephew died in a rural area wehn he fell into a pond.
Anywhere in the city it wouldn’t have happened. I fished toddlers out of the city park pond my own self.
It is hard to know what to make of this. A study about how people who swim more than others have a higher incident of ear infections would make about as much sense as this study about “urban heat.” Did I miss the part in the paper that states that a high percentage of Stevenson screens reside in urban areas?
JimS, you hit it right on the head! The alarmists have been claiming that UHI is not significant. This study supports what we have been saying for a long time. UHI is producing warming bias in the surfac sensor temperature records. And this is why we perfer to use the satallite records; which due to excluding UHI bias, show less warming than do the ground based temperature records.
So how does this fit in with the usual warmist position that UHI has no noticeable effect on local temperature ?
exactly right… finding fits perfectly with UHI… In Melbourne Australia UHI has been shown to be as much as 6 degrees(C)… which also fits with the finding that minimum temperatures (overnight) are increasing but maximums generally are not.
Cheers
J
Quite right, Jim!And, the socialist government planners can only see cramming more people into concrete edifices in the cities as a salute to their silly religion. Wendell Cox was right, urban ‘sprawl’ is better than aggregation in the cities.
It’s called “New Urbanism” and “Smart Development”. If you want to get a project through in a jurisdiction which subscribes to this nonsense, remember to emphasize “Livable, Walkable, Sustainable, and Green” in your presentation to the Council.
It’s also called “Smart Growth”. I don’t know a single developer, including myself, who hasn’t lost his butt initiating one of these projects. The trick is to buy it from the third guy who went broke or died trying to get the permits. The last one I did took 16 years, after the first and second guys, both of whom are now dead; in fact the partner with whom I pulled it off on the third try is dead.
Now that I think about it, the guys we sold it to, #4 in the chain of title, still haven’t completed the project.
So, instead of UHI temperature readings causing an exaggeration in global warming, global warming is causing UHI. Is that what they are trying to claim?
Yeah – when life gives you lemons, make lemonade.
…or in the case of the warmunists, pee in a pitcher and sell it as lemonade.
Gross!! Made me laugh though.
Quite so. Global warming is man made, and is worse in cities, also man-made. Can you see a pattern here? Well man-made things are causing UHI.
So Carbon Dioxide is an intelligent molecule then. It knows how to selectively target urban areas for extreme heat and precipitation. Does it do it out of revenge? Or is it thanking humans for setting it free from its fossil-fuel prison? After all, it is also making winds more gentle in the urban areas where humans tend to live. So perhaps CO2 is more intelligent than most climate scientists and knows that a little more nighttime warmth and a little more moisture are actually good things. I’m just worried about what it might do to us if it ever gets “wind” that humans have designated it as “carbon polution” and are out to eliminate it. I sure hope that message takes a long time to get well mixed into the atmosphere. Next ice age, here we come! /Sarc
The hotter the day, the more heat the cars’ and buildings’ air-conditioning pumps to the out-of-doors, which in turn causes them to increase the air-conditioning, which … well, we now know what causes man-made global warming. \sarc
Louis, you hit the nail on the head!
The cart is officially put before the horse. These guys have endless illogical explanations about the simple weather. I say we escort all of them to the nearest sanitarium for mental health issues.
The entire research can be summarized in terms of three items:
1) The researchers identified about 650 urban areas with populations greater than 250,000 and then refined the list to the 217 locales based on the areas’ proximity to weather stations with complete weather records and NOAA data — most were located at airports close to urban areas
2) “Our findings suggest that urban areas are experiencing a kind of double whammy — a combination of general climatic warming combined with the heat island effect, wherein human activities and the built environment trap heat, preventing cities from cooling down as fast as rural areas,”
3) said Dennis Lettenmaier, a co-author of the study and a UCLA geography professor
Translated to the vernacular:
1) if you are a hammer everything looks like a nail
2) the drunk always looks for his missing keys under the street light
3) those who can’t do proper statistical analysis teach geography
There are clearly places on the earth [e.g. midtown Manhattan] where the technological heat input exceeds the natural heat input to the local environment by a large factor. What would have made the study semi-useful would have been to measure the correlation between kW/capita and kW/m^2 and the UHI effect
‘most were located at airports close to urban areas, ‘
Weather stations at airports are designed to be used to give information for flight movements and and out of the airport , they are not designed to give this information for the wider area , they are used in this way because ‘they are there’ not [because] they are good at it .
Airports may not even be typical of the area they are sited in, modern airports tend to out of cities because that is where the free land is , but the surrounding area can still be rural. In fact very few areas have such big open areas of concert and tarmac in the way airports with their runways, pans taxi lanes, have . If you ever work at one you
Its like using a weather station [on] top of a mountain to represent the weather conditions in the valley below mountain because it ‘there ‘ and not far away , and then expecting to get honest results.
WestHi – There are clearly places on the earth [e.g. midtown Manhattan] where the technological heat input exceeds the natural heat input to the local environment by a large factor.
Back in 2010, I posted the following analysis on New York City power usage as it related to UHI.
DD More February 26, 2010 at 7:22 am
I could never understand how UHI was minimized. If you look at New York City as an example.
Area, including water 468.9 sq mi ( 2,590,000 sq m)
Power used (2008) 54,869 GW-hr
(http://www.nyc.gov/html/planyc2030/downloads/pdf/progress_2008_energy.pdf)
Watts/sq m = 2,416 total. The Mayor says 80 percent is used by buildings and therefore 100 percent ends up as heat loss. So the forcing is 1,933 W/Sq M
The file also remarks that the city has seen a 23 percent increase in the last 10 years, which is close to the increase showing up in the charts.
http://wattsupwiththat.com/2010/02/26/a-new-paper-comparing-ncdc-rural-and-urban-us-surface-temperature-data/#comment-329553
Well it should be updated a little. Clarifying the 80 percent used by buildings was for lighting and heat, so by next day at the same temperature it was all turned to waste heat. I heard later that Reliability concerns require that 80% of the City’s peak load be met with in-City resources under a mandate from the New York State Reliability Council and the New York Independent System Operator.
The original calculation would now be 54,869 GW-hr / year * 1.0 x 1.00E+09 W/GW x 8760 hr/yr = 6,263,600,000 W-hr / hr. that divided by 2,590,000 m^2 = 2418 W / m^2 each hour. But if you take at least 60 percent of power generated in the city generates 40 percent excess waste heat to convert to electrical power = 2418 x (1+ .24) = 3000 W / m^2 of extra energy being dumped in the air of New York City. And that is from electrical power alone, doesn’t include all the vehicle waste heat.
So does 3,000 w / m^2 raise the temperature more than 100 ppm CO2?
But when you remove UHI from the equation the overall temperatures go down. More.
I have said this in the past. I am in a small town in rural Montana and there is a 6 degree temperature differential within four blocks of the two thermometers. One is surrounded by all cement and the other is elevated and above gravel and dirt. I call this the cold island effect. It is more noticeable the colder it gets.
You didn’t say which reading was 6 degrees higher. Was it the concrete area or the gravel/dirt area?
The thermometer right near the cement is lower.
That could explain why winter temperatures don’t show the UHI effect as much as spring and summer.
In cars with digital thermometers, one can see the temperature rise going from country to urban areas – discounting those variables that add or subtract to the effect. (It would be interesting to digitally store the temps during a trip, and then plot them out, superimposed over a map of the route taken.)
noaaprogrammer
Anthony did this experiment a few years ago using some of his temp and humidity monitors mounted on his car as he drove through his local town one evening all tracked but GPS the results were posted for us all to look at just how much the temp fell away from the middle of town.
James Bull
I live 1 mile outside of a small rural town in Ohio (6,000 people) and during cold January, February mornings it is 12 degrees warmer in town than 1 mile outside of town. No elevation change either it is flat land for miles around.
Jared,
That is due to the RHRE, or Rural Heat Rejection Effect, for which you are personally responsible. Either pay up or move into town, where it is warmer. Your masters demand it. (See Al Gore to sign up.) Sarc/off
(And take your bleeping thermometer with you…)
Remember though that our small little town in the middle of nowhere is considered rural where UHI should not even register. I doubt any of the Gavin’s or Hansen’s of the world have ever done a field study in a true rural place. They have blind faith in the omniscience of their flawed computer algorithm. Hey Gavin, do an actual field study in a truly rural place in the middle of January. Tell us again how UHI is negligible. I forgot your algorithm is infallible.
Urban heat island?
Concrete?
This result is about as significant as stating “empirical evidence shows that daily temperature ranges are far greater in desert environments than they are in coastal environments”.
Duh.
“Dark is most prominent at night”
Don’t laugh. I once worked for a company whose industrial engineers did a study trying to figure out why the night shift used more flashlight batteries than the dayshift. Should have been a gov’t grant proposal.
Someone in the past reported here on the difference between urban and rural temperature readings. It would be very interesting to do that again for 2014, “the warmest year on record.” I’m curious about how much difference there is in both the raw data and the adjusted data. I would be very surprised if the rural areas are not being adjusted upward to make them more closely match nearby urban readings. Anyone willing to take that on?
There must be a reason why their study 650 urban areas was winnowed down to 147 rural/urban pairs there at the end. That’s because rural stations aren’t condusive to their lie. So inspite of “Urban areas make up a relatively small part of the global land area” it’s the rural stations that get closed up, discontinued, deleted from the network.
Sound the trumpets. Warmenologists discover UHI. Film at 11.
I wonder what this means for a city such as Vancouver, BC. The hottest of the hot days in that city is still about 10 C cooler than a city like Spokane WA. The hottest temperatures I have ever experience was 40 C in Winnipeg during a stop over for 4 hours in 1988, and 40 C on a tennis court in Spokane WA in the late 1970’s. I also experience great heat while traveling through Osoyoos a couple of decades ago whereupon a nice large iced drink solved that problem.
The summer heat of Spokane is such an alien experience to me having spent most of my live on the south west coast of British Columbia, so much so that I was amazed at how hot it still was late into the evening when visiting family there. While planning a swimming adventure out of town at a French named lake Coeur d’Alene in Idaho, the temperatures dropped on the day of the outing so much that it was too cold to swim.
I ride my bike a lot and get to experience local micro-climates and have discovered, for instance a noticeable cooling when I approach the entrance to Hyde-Creek Park, several blocks before the entrance. Note the Creek is dried up in summer so the cooling is from the mass of trees. I have experience cool spots while riding on the dike and noted the coolness was related to the proximity of the river to the edge of the dike.
I am working on a very complex computer model to more scientifically determine for example the global average temperature of the earth. Several years more work to do. Gotta go, a couple more years of study still to do also.
Ass fault.
“Urban areas experienced 60 percent fewer extremely windy days than non-urban areas.”
Winds aloft or down between the tall buildings? Vertical “winds” or horizontal winds? As every pilot who’s been there knows, on sunny days you hit a major updraft as you pass over the parking lot on short final to RWY’s 25 R&L at LAX.
And for some reason I’ve never understood, as you depart LAX on a warm day, it gets cooler once you cross the beach and head out over the Pacific. /s
Looking forward to the audit of the Bureau of Met in Australia. I can see the skyscrapers from my farm where we are always several degrees cooler than the official thermometer.
ACO2 hasta cause cooling. ☺
Its not going to be an audit, its going to be a “forum” whatever that means, i guess a bunch of BOM friendly people are going to sit around and chat about those nasty malicious rumours and decide that no such thing actually occurred, then they will write a report and the ABC will yell nya nya na na na, Iwe told you so…….
The concrete message is that all of us denierers should get down on our knees and gravel.
‘…Lettenmaier said. “You have heat being stored in buildings … they don’t cool down as quickly… This effect was likely exacerbated by decreasing wind in most of the urban areas.”’
Well, that’s it, we should all sleep on the ground. What do these morons expect? Don’t live in a private home. But don’t live in a building. Don’t live in the city. But don’t live in the country. But, definitely don’t live in a suburb. Don’t drive. Don’t fly. Don’t use your AC. Don’t use your washing machine. Don’t even buy a washing machine unless it’s a front loader. Don’t use a dryer. Don’t use electricity when we don’t think you should use electricity. Don’t have a pet dog. Don’t eat beef. In fact, don’t eat meat. Don’t drink soda pop. But don’t drink water. Don’t flush your toilet. Don’t take a shower unless it’s a dribble.
Enough alright already. The U.S. Constitution does not tell the citizens what they can’t do. It is a blunt statement on what the damn government cannot do. It’s about time we demand that these, “first of its kind”, “unique”, “new approach”, and so on, and so on, “revolutionary” studies stop sucking up our hard earned money.
They got it at the end. “In urban areas, buildings are disrupting the air flow, which affects not only the immediate area of buildings, but apparently the larger regional wind fields,” Lettenmaier said. “The reduction in wind may well be exacerbating the heat island effect.” Or call it no breeze.
Yes! Walls block wind ! Who knew ?! …Maybe the Great Wall of China was really built to cause” Climate Change” !… /sarc …
Maybe it was! The ancient Chinese were pretty bright and maybe their wives were complaining about the cold…
Has Dennis Lettenmaier ever heard of the Urban Heat Island effect? That is one reason the “data” has been adjusted to show global warming. I don’t think Dennis Lettenmaier has been reading his WUWT to being kept up-to-date on the subject…
“The researchers identified about 650 urban areas with populations greater than 250,000 and then refined the list to the 217 locales based on the areas’ proximity to weather stations with complete weather records and NOAA data — most were located at airports close to urban areas.”
Increases is flights? Those places are busy with mega space heaters.
Used to be called the “Air Field”, then it was called the “Air Port”, now it’s the “Air Terminal”. Apparently caused by Global Warming.
Where I live in Canberra, I am about 400 meters from a BOM weather station. I always use to a direct reference to it from the BOM website. Unfortunately, in the last two years an elder care facility was completed about 150 meters away. I have noticed an increase in the average temps. So much for no UHI influence.
Interestingly, the “official” weather appears to reported from the airport. Who lives at the airport??
Worse ‘Bear … the Steveson screen could be located at the Federal Parliamentary buildings !
Sorry for the typo, that should have been “Increases *in* flights?”
So my guess is that Dennis Lettenmaier got his degree in Geography at Disneyland.
Well, It’s a small world after all!
Too many people, crammed into not enough space. Cars everywhere. Tall buildings everywhere. Every bit of green space is covered with concrete or asphalt. What on earth did they expect? Agenda 21, is not a good plan…..
So the more people, cars, buildings, increased energy use and waste within a concentrated area the greater the heat signature for that specific area .Who would have ever thought this, what a startling discovery.
Next up for a critical scientific break-through relates to the studies that are close to determining whether night follows day or day follows night.
Disneyland, home of conservative Orange County anti-vaxers. Most are also CAGW skeptics, an irony I’ll never understand.
Alx: Before your study can be done, these climate scientists need to complete the current study they are doing. They are trying to determine in what order do the seasons occur (a,w,s,s or w,s,s,a or s,s,a,w or s,a,w,s). Once this is resolved they will look into the night / day / night thingy you raised.
Speaking of concentrating,
http://www.weather.com/science/news/london-walkie-talkie-building-sunlight-beam-melting-cars-20130903
Has anyone ever calculated the heat generated by braking systems, whether by automobile/truck/train or aircraft?
At YYZ (1990’s) the smell of burning rubber from aircraft tires hitting the runway was never far away.
APU exhaust goes with the flow.
Aircraft manufacturs have calculated brake and associated hydraulic fluid temperatures and their effects on performance since at least the days of the B-29; but don’t tell Bill Nye. He would suffer debilitating cognitive dissonance in spite of the fact he once worked for Boeing. 😉
Has anyone ever calculated the additional heat generated by plonking a PC on everyone’s desk, many of them left running 24×7? Maybe the pause is down to the emergence of fondle slabs /sarc.
Automobiles and trucks release a large enough amount of heat from the exhaust and the cooling system that heating from brakes would be a minor effect. This is even more pronounced by modern aircraft where the heavy braking is done by thrust reversers on the engines. Modern electric trains tend to use regenerative braking where much of the energy released by braking is turned back into electricity,
That said a large road even when there is no traffic tends to a hot place in summer especially when it has a black asphalt surface. Even in the UK I have seen melting tar on roads in summer.
Don’t need to calculate it, the energy to “generate” the heat comes from burning the fuel to make the vehicle move in the first place, and we measure that.
In addition to infrastructure development, over the past few decades there has been a vast deployment of HVAC systems, electronics and wires/cables of all types. All of these produce heat, which adds to the impacts caused by infrastructure/albedo modifications. I’m noting the exhaust out of my laptop as I write this!
Good point. As I write my computer system’s power supply indicates a draw of 175 watts, and some of those are definitely generating heat.
Rather, ALL of those 175 watts are generating heat. But, on a winter’s night, those 175 watts are “replacing heat” not otherwise needed in the house that come from your furnace. On a summer’s afternoon, those 175 watts added indoors to an air conditioned space would be adding to your street’s electricity needs. However, to get those 175 watts inside your house on your lap, the power company needed to generate some 195 to 205 watts depending on where your house is. To generate those 200 watts at the end of the power station transformer, the power company needed to create 400 to 500 watts in their boiler or gas turbine.
You, yourself, are also adding heat just by sitting there … about 100 watts per person.
What on Earth has hundreds of thousands of tons of concrete got to do with anything?
Well obviously the CO2 generated by its production and transportation to job sites lingers overhead, creating the UHI.