A recent article posted at Oilprice.com claims that recent warming trends in Phoenix, Arizona are due primarily to increasing atmospheric carbon dioxide levels in the atmosphere. This is false. Data show that the high levels of warming, especially at night and as measured at an airport, are primarily due to urbanization over time, with the modest warming of the past hundred-plus years playing a very small part in comparison.
The article, “Explaining The Heat Wave: Separating Weather From Climate Change,” written by Robert Rapier, begins by correctly identifying the difference between weather and climate, explaining that weather is a shorter term event whereas climate is over “years, decades, or centuries.”
What is not true is Rapier’s assertion that the warming over the past 50 or so years in Phoenix has been mostly driven by climate change caused by rising atmospheric carbon dioxide levels, and worse, that the trend will cease only when people curtail emissions of carbon dioxide.
The top ten hottest years in Phoenix have been in the last 20 years, Rapier says, and the ten coldest are mostly from earlier in the 20th century. Atmospheric carbon dioxide concentrations are one thing that have changed since 1900, this is also true, but another factor that has a more immediate effect has changed as well.
Rapier even makes a comment that lends us a clue to what is going on.
He writes:
One of the biggest problems faced by cities like Phoenix is that the nights aren’t cooling off as much as in the past. For example, in the 1970s the average low temperature in Phoenix was 59 degrees F. During the previous decade, that had risen to nearly 65 degrees. That’s a substantial increase for an annual average.
This is a known effect of the Uban Heat Island (UHI). As described by meteorologist Anthony Watts in “No, E&E News, Climate Change Has Not Caused Reno’s Rapid Warming,” the UHI is seen most clearly at night. This fact has been confirmed time and again, including for Phoenix itself. Phoenix’s nighttime low temperatures are reported by Arizona State University researchers to be 10 to 15°F higher than surrounding rural areas. An illustration of this effect can be seen in the thermal image of Phoenix below, where the city and rockier mountain areas are hotter than the surrounding rural parts of the region.
The UHI is because of the heat-absorbing property of concrete, asphalt, and other construction materials that make up cities. During the day, they heat up, and at night, release the heat of the day into the surrounding air. Additionally, heat sources like engines and air conditioning units contribute to higher city temperatures.
Arizona isn’t alone in this. The University of Nevada study “The Urban Heat Island Effect in Nevada” found that cities with over 1 million residents can be 1.8-5.4°F warmer during the day than surrounding areas, and over 20°F warmer at night.
In 1960, Phoenix only had a population of about 100,000 people. Today, it is over 1.6 million.
Climate scientists at Georgia Tech told the Associated Press in 2018 that research shows Phoenix’s UHI causes the city to warm at three times faster than the rest of the world – meaning that climate change itself cannot be the main driver of Phoenix’s extreme highs, especially at night.
Fairly egregiously considering what we know about UHI, Rapier admits that the recent record high daily low was measured at Sky Harbor Airport. That temperature station sits downwind of the tarmac. (See image from Google Earth below)
Consider, for comparison, Chandler Arizona, which is very close to Phoenix but has a much lower population of 275,987. On the night that the Sky Harbor Airport hit the record daily low temperature of 97°F, July 19th, weather stations in Chandler recorded lows closer to 86°F. That is an eleven-degree difference.
In fact the airport station itself appears to be inflating temperatures even within Phoenix, because other nearby stations downtown recorded nighttime lows closer to 92°F. This airport data is where Rapier’s decadal average lows data quoted above comes from as well.
Climate Realism has catalogued plenty of similar scenarios where the UHI inflates average highs and especially nighttime lows, here, here, and here, for just a few examples.
The closest Rapier gets to acknowledging the UHI is in one short statement towards the end of his essay, after explaining the influence of El Niño, “[l]ikewise, there are other factors that influence temperature,” he says. “That’s why global temperature doesn’t scale linearly with rising carbon dioxide temperatures.”
Close, but no cigar.
Even back in 2012, the American Meteorological Society published a paper describing how the UHI in Phoenix could be studied, as well as mitigated using carefully planned tree plantings and vegetation. The study references the Phoenix Urban Form project, which sought to do city planning with UHI in mind back in 2006. This is not new information.
Rapier should have considered all the factors that may be leading to higher temperatures in Phoenix instead of jumping straight to carbon dioxide as the main culprit. Although the average temperature of the planet has modestly warmed over the last hundred years, the influence of the Urban Heat Island effect is a much stronger local explanation for Phoenix warming trends. It would benefit Oilprice.com and their contributors’ trustworthiness to acknowledge these effects. Instead of pushing for an end to carbon dioxide emissions, they could push instead for local policies that help mitigate the UHI.
Linnea Lueken is a Research Fellow with the Arthur B. Robinson Center on Climate and Environmental Policy. While she was an intern with The Heartland Institute in 2018, she co-authored a Heartland Institute Policy Brief “Debunking Four Persistent Myths About Hydraulic Fracturing.”
Elevated nighttime temperatures relative to the countryside is the signature of UHI.
Afternoon maximum temperatures are also affected. They should really plant more vegetation all over the city. I feel bad for the people living there.
Do not feel bad for those of us that live here.
I moved from snow country to Phoenix 8 years ago and haven’t regretted it at all.
Most places have at least 3 months a year that going outside is miserable.
Summer can be brutal, but the city doesn’t block my driveway full of sunshine every time the plows come by.
My vehicle isn’t rusting in the driveway.
I can drive 1.5 hours north and cool off in the mountains.
Vegetation exists, but it’s low water usage plants, or non-potable water usage for the grass areas.
Phoenix is definitely a choice. There are other places to live, but millions choose to live there.
Yep. Google says 4.9 million of us live in the Phoenix metropolitan area.
Watching the news at 10pm routinely shows the surrounding areas of Phoenix are 3-5 degrees cooler.
I dId my hike this morning but made sure to be finished by 10am.
Just another beautiful summer day in central Arizona – completely consistent with “climate change”. LOL
Needs lots of water… just sayin..
Often we do but we are careful about what we plant. I have orange bells that seem to get along well with 3 gallons of water a week. Some desert trees and bushes but grass is really a no no. It takes a ton of water, something we have little enough of.
Remember, we go from our air-conditioned place of work to our air-conditioned car to our air-conditioned store, back to our car and then to our air-conditioned home. We hardly feel the heat.
Are the reports that Phoenix and the county (Maricopa) in which it exists is the fastest growing area in the United States false? That isn’t a UN camp for displaced people, it is a destination of choice for those who can manage to get there. You feel bad for people achieving their goal?
I imagine that people living there would prefer it not to get above 110 degrees. Do you like that lol?
110 degrees Fahrenheit is a nice round number and a normal summer day.
A large swath of the United States regularly reaches above 100 degrees Fahrenheit every summer.
It is weather and many many people are fine with their weather.
Phoenix is a destination state for golfers, hikers, runners and tennis players. It is an extremely popular state for retirees that like to be outside a lot.
If you haven’t been there, and it shows, then you cannot suggest changes.
Phoenix is arid country, desert is a proper description.
Water is valuable and except for golf courses, not wasted on lawns and grass.
Indeed, many people living in Phoenix have rocks, stones, pebbles, gravel, etc. for their yards.
Quite a few plant native to Arizona plants. Plants that can survive and thrive on Arizona rainfall levels.
Adventurous Phoenix residents plant citrus trees which they have to water to keep alive. Except a freeze not too long ago took out a lot of the citrus that I had seen growing.
Phoenix residents that want to protect their properties, plant ocotillo, fouquieria splendens. Others plant barrel and paddle cactus for their flowers and greenness.
It takes a very long time for cactus to grow big enough or tall enough to make a thermal absorption difference.
If Phoenix painted everything white or even yellow sand color, it would be blinding even when wearing sunglasses.
All in all, Phoenix is a darned nice place with consistent very dependable bright sunny clear sky weather.
I wondered how the city got its name. Apparently one Darrell Duppa predicted the rise of another great civilization on the same site as long gone Hohokam. Duppa compared the phenomenon to the mythical Phoenix bird in Egypt that lived 500 years, then rose from its own funeral pyre to flourish again.
https://arizonaoddities.com/2010/01/how-did-phoenix-get-its-name/
There’s a fiery theme in there…
Part of the history we used to be taught in grade school.
https://www.phoenix.gov/pio/official-city-bird-logo/history-of-the-city-bird#:~:text=The%20phoenix%20bird%20symbolizes%20immortality,Arabia%2C%20near%20a%20cool%20well.
Robert Rapier has written many articles on the failures of renewable fuels projects such as Range Fuels which was proposing gasification of wood waste and synthesis of alcohols from the syngas produced, and the failure of KIOR which spent $2B on development of a woody pyrolysis to fuels project that was a spectacular failure. There are such projects that can succeed, but these two were doomed from the beginning due to terrible choices of technology. Rapier’s articles on these failures were accurate.
Sad that he got this on so wrong.
In the oil shock times of early 70’s and 80’s people tried to find ways to use what was then called “thermal mass” to capture the heat from bricks etc.
Just fire the phaser at the rock…
G’Day mkelly
“thermal mass”
Known as a Trombe wall. Had a friend in Ridgecrest, CA, whose house had one. He swore by it.
This is a good report, especially marking the UHI effect as a major issue. I remember my geology traverse on the north side of Phoenix, in a July about 1985, when it was 116 deg F. When we were picked up and drove to the nearest Stop-and-Rob, to buy cold drinks, we saw several men on a flat roof, applying tar. The tar was hot, the roof was black and extra hot, and each of the workers, without shirts, were so dark you couldn’t tell what their start genetics were. This leads to another problem with the CAGW nonsense: workers now have become sissified. Seen any workers in similar setting recently? Sissified.
We still continue the tradition of starting work as soon as there is enough sunlight to see and quitting about 2 in the afternoon. That is one of the reasons we don’t go on daylight savings time. That type of heat can kill so we have always avoided as much of it as possible.
UHI is very real, even in small cities. I live about 4 miles outside one of those (> 100K residents – small enough you could walk from one end of town to the other in an hour or less). When I come home from work at night (in town) I can watch the temp reading in my car drop 5 degrees or more. 80F in town and 74 at my house. And this is in a mostly rural area with a small city that serves as the county seat. This effect happens both in summer and winter, but is more pronounced in summer.
And then there is the issue with siting of weather stations. When the nightly local news comes on, my nearby city is nearly as hot as Baltimore – which is far larger and some 30 miles away…. I don’t know where the weather station is located, but it surely must be surrounded by lots of asphalt. And maybe near the discharge of an AC unit. There is a small airport in town, perhaps that is where they measure the temps reported on the news.
If the news says it’s 95 in my town and 97 in Baltimore, it will be 88 at my house…my weather station is in my yard, with grass and trees – away from the road and my paved driveway.
But sadly people simply ignore this phenomena, at least those who are trying to demonize CO2. Perhaps having thermometers in cars is a good thing – maybe more people are realizing that most devastatingly high temps are only those recorded in cities!
Yep – ‘climate change’ is a purely urban condition.
Just going up 1000′ from the ocean into the mostly spruce forest in summer gets you 5oC on a sunny day. In winter you lose 5o in the same trip.
Hi Fran,
You can get the degree symbol by either “copy and paste” or on many keyboards by holding down the “Alt” key and typing 0176.
Regardless, we know what you intended. 🙂
Phoenix also has a water problem. no? Scientists say the Colorado river is not receiving the runoff from the snowpack that it used to….seems 10% of the snow in the mountains was always going sublimation but now 20% or more is being lost to sublimation for some reason.
Rain fall is average and the weather cycle can run over 10 years around here. The estimate of the Colorado river flow was made during a wetter than normal period and allocations were based on that. Unfortunately several states rely on that allocation calculation so they overdraw during the dry years.
One of the reasons you find abandon Indian ruins around here is probably because the little ice age caused dryer than normal conditions requiring the population to either move or die. Unfortunately that time period isn’t studied from a climate view point and I may be putting 2+2 together and getting 5.
Phoenix on the other hand was originally set up with water storage that could go 7 years without any rainfall. Unfortunately with the population increase there isn’t that much storage today and they needed to tap into the Colorado river.
At a friend’s house, last Tuesday evening, I leaned against a dark-stone wall. The Sun had gone down 1/2 hour earlier. I know the concept, but the immediacy and amount of heat surprised me still. Dark tree trunks and fence posts do the same. [I do not live in a town or near a large city.]
I plan to put a temperature sensor on one of these things and see how long it takes for the heat to dissipate. A time-lapse IR video might be interesting — likely not going to do that.
A data logger would be even better.
Does anyone realize that over 80% of the electrical use of a city goes into comfort. All that power to light, heat/cool, and run convenience machinery is converted to heat.
How is the city’s power usage grown over the last 30 years.
Additionally, when you drive a car and park in the same spot each night, there is no change of energy, so all the fuel used has been converted to heat.
Does Phoenix have the same traffic as 30 years ago?
Under what circumstances would the fuel energy NOT be converted to heat?
Entropy always wins in the end but something useful can be accomplished between beginning and end.
Don’t forget that the entire electrical wiring set up also generates heat from resistance in the wire and various components along the way – it may not be a huge amount by itself but there is a lot of wiring and it all adds up.
Very nice Linnea.
Maritime Executive has gone woke too.. Will the Enron fiasco ever go away?
https://www.maritime-executive.com/article/low-sulfur-fuel-rules-may-have-contributed-to-record-ocean-temps
Wow, a picture of my house, sort of. Left corner of the picture where the two mountains come together and about 10 mile back. Anyway what everybody tends to forget is in the 1960 it was very common to use evaporative coolers instead of air conditioners. They would suck in outside air, run it through wet pads and in a minute or two it would be dumped outside again. This had to result in a net cooling of the area. In addition, the waste water from the cooler was often drained out and used to water the lawn. Coolers are still used today but they are rare and often limited to commercial applications like manufacturing were doors are open to the outside most of the day.
Another mistake is the valley population was near a million in the 60s. Today it’s near 5 million. People tend to forget that Phoenix proper is only a small portion of the population in the valley of the sun. I give my location as Phoenix but that isn’t what my address is.
Hi Dena, I’d guess Arizona is one of the best places to use evaporative coolers – very little danger of ‘excess humidity’!
During monsoon season July through September sometimes the dew point get in the 60s and they don’t work real well. When the dew point is below freezing you find yourself reaching for the heavy blanket in the morning. That is probably one of the best reasons air-conditioners have become more popular however I noticed that bare steel will sometimes get a very thin layer of rust on it.
I must point out a serious error this and other very intelligent persons make regards airport weather stations. Not to detract from an otherwise excellent article, but consider the following:
Weather stations sited on airport grounds, usually between taxiways and runways, but sometimes on concrete or asphalt aprons are indeed correctely situated and properly fit for purpose! That purpose being for essential and critical safety of both general and commercial aviation!
Aircraft must determine the actual conditions on the runways to determine if they have enough performance given their intended takeoff weight to become airborne in a safe manner. Thus if the runways and aprons and taxiways make the air hotter on the airport grounds, the flight crews must have the actual air temperature, pressure and dewpoint of that air their planes will be taking off in!
It is extremely critical as air temperature and density are directly related to how much lift the wings can produce and how much thrust the engines can generate. Both a weight and balance determination and a performance determination are done for each and every takeoff for every commercial aircraft from a small commuter twin turboprop to a 747 or A380.
Similarly all landing aircraft must know the actual air conditions for the same kinds of performance calculations for landing and stopping distance, and ASOS AWOS and ATIS information are broadcast on aviation comm frequencies for this purpose.
What is not fit for purpose is using airport weather data for climate analyses. But the airport weather data [on actual runways] is extremely critical for safe aviation. So people, do not lobby, lament or attempt to change airport weather sensor locations, direct your ire to those misusing this critical safety data for climate alarmism. Unfortunately, airport weather stations report their data every hour, and a record of this is extremely reliable, so the data tends to get lumped into general climate analyses because airport data is so regular and goes back a long way too. (unfortunate in that it gets used for the alarmist narrative)
One of my local TV station’s weatherman would always state the airport temps, and he would put a caveat that it was almost always 2-5 degrees F warmer than the actual temps away from the airport. But he has retired and all the newbies have swallowed the alarmist kool-aid.
Bottom line – pilots must know the actual air temp, etc of the air over the runways for safe operation of their aircraft – so airport weather sensors are correctly sited; just don’t use the data for other purposes because it has a serious UHI bias.
Yup. Many of us have made the exact same point on WUWT over and over again without it registering with the climate enthusiasts who seem to have a monomania with warm temperatures, no matter what errors or outright falsehoods they propagate by using them. Airport and bases temperature stations should be for the sole purpose of aircraft, nothing else!
I remember a time when my young feet learned a lesson at the beach. To get to the water you had to run as quickly as your little legs would take you, lest you burn your feet on the bone dry sand that separated you from the cold sand at water’s edge.
If you couldn’t stand the pain you could stop and burrow your feet down a few inches to cool your soles. The dry beach surface represented a thin insulated layer of stone that could only shed its energy by raising its temperature high enough to match the incoming shortwave with its own outgoing long wave. There was little conduction downward through the sand below.
Urban landscapes are analogous to the beach. They are intentionally designed to keep the subsurface dry. The only way to shed incoming energy is to radiate it away.
Two things happen in this artificial environment. Surface to air conduction is massively enhanced by increased delta T at the surface, and of course, all the structures above ground become daytime heat sinks for later nighttime energy release.
As in all things with heat, it is a far more complex environment than UHI caused by heated concrete alone. Painting everything white and growing a few trees won’t save the cities.