From Dr. Spencer’s Global Warming Blog
by Roy W. Spencer, Ph. D.
This is the first of what will likely be a series of posts regarding urban heat island (UHI) effects in daily record high temperatures. My previous UHI work has been using the GHCN monthly average station data of “Tavg” (the average of the daily maximum [Tmax] and minimum [Tmin] temperatures). So, I’m moving from Tavg to Tmax (since record high temperatures are of so much interest), and daily rather than monthly values (although I will also sometimes include monthly results to provide context).
This post is mostly a teaser. Toward the end I will describe a new dimension to our UHI work I’m just starting.
The 2024 Poster Child for U.S. Warming: Palm Springs, CA
I was guided by a Google search on U.S. record high temperatures for 2024, and it seems Palm Springs, California was the place to start.
With a name like “Palm Springs” this place sounds like a wonderful spot to lounge under palm trees and enjoy the cool, refreshing spring water that surrounds you. Instead, the location is largely a desert, with the original downtown spring spitting out 26 gallons a minute of hot water. The “palms” do exist… they are “desert palms”, naturally growing in clusters where groundwater from mountain snowmelt seeps up through fissures connected to the San Andreas fault.
Like all U.S. metropolitan areas, the population growth at Palm Springs in the last 100+ years has been rapid. Even in the last 50 years the population has nearly doubled. Natural desert surfaces have been replaced with pavement and rooftops, which reach higher temperatures than the original desert soil, and the “impervious” nature of artificial surfaces (little air content) means the heat is conducted downward, leading to long-term storage of excess heat energy and, on average, higher temperatures. More on “impervious” surfaces later….
The Palm Springs Airport Weather Observation Site
The following Google Earth image shows the current location of the official ASOS (Automated Surface Observing System) site at the Palm Springs Airport, which recorded an all-time record high temperature of 124 deg. F on July 5 of this year.
What is somewhat amusing is that ASOS meteorological instrument siting guidance favors natural surfaces for placement, but since most of these weather stations are at airports (and since they primarily support aviation weather needs, not climate monitoring needs), the “natural” location is usually right next to runways, aircraft, and paved roads.
The next Google Earth image is zoomed out to show the greater Palm Springs area, with the ASOS site in the center (click on the image to zoom, then click to zoom more).
Record July Temperatures and Urbanization
It only makes sense that people want to know the temperature where they live, and most of the U.S. population resides in urban or suburban locations. Yet, the temperatures they experience are, probably without exception, higher than before people moved there and started building roads, buildings, and airports.
But what is misleading for those following the global warming narrative is that record high temperatures reported at these locations almost always mention climate change as a cause, yet they have no way of knowing how much urbanization has contributed to those record high temperatures. (Remember, even without global warming, high temperature records will continue to be broken as urbanization increases).
As mentioned above, on July 5, 2024 Palm Springs broke its all-time high temperature record, reaching 124 deg. F. There are 26 other daily GHCN stations within 40 miles of Palm Springs, all with varying levels of urbanization, but even more importantly, at very different elevations. If we plot the high temperatures reported for July 5 at those stations as a function of station elevation, we see that Palm Springs is an “outlier”, 5 degrees warmer than would be expected based upon its elevation-corrected expected temperature (the dashed regression line):
Now, keep in mind that many (if not most) of those 26 surrounding stations have their own levels of urbanization, making them hotter than they would be in the absence of pavement and roofs. So, that 5 deg. F excess is likely an underestimate of how much urban warming contributed to the Palm Springs record high temperature. Palm Springs was incorporated in 1938, and most population growth there has been since World War II.
If you are curious how the previous plot looks for the average of all July temperatures, here it is:
For the month of July, Palm Springs averaged 3 deg. F warmer than the surrounding stations (after adjusting for elevation effects, and keeping in mind that most of the *other* stations likely have their own levels of urbanization).
Clearly, Palm Springs has had spurious warming influence from the airport and surrounding urbanization which did not exist 100 years ago. But how much?
Impervious Surface Data as a Surrogate for Urbanization
This blog post is a prelude to a new project we’ve started where we will compare daily (as well and monthly) temperatures to a relatively new USGS dataset of yearly impervious surface coverage from 1985 to 2023, based upon Landsat data. I had previously experimented with a “Built Up” dataset based upon Landsat data, but it turns out that was just buildings. The “impervious surface” dataset is what I believe will have the greatest direct physical connection to what causes most UHI warming: roads, parking lots, roofs, etc. I think this will produce more accurate results (despite being only ~40 years in length) than my population density work (which is, we hope, close to being accepted for publication).
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A great place to be from!
Does the population go down in July?
“Does the population go down in July?”
My husband and I spent a couple of weeks in the Palm Springs area about 10 years ago, and we were told that the condo rentals are practically nil in the summer.
I’m reminded of Bill Paxton in Aliens – “Yeah, but it’s a dry heat.”
Airports seem to be a popular site for bad temperature readings.
Pilots don’t think so. It is the use for “climate” research that is improper.
As Roy has demonstrated.
I don’t think “climate research” is really about climate but can accept episodic weather.
In this context I don’t like the term “cyclical”, although others use it frequently.
Pilots need the accurate real time air temperature to assist in safe takeoffs and landings.
That aside, those temperatures are not accurate in any kind of global trend analysis.
Or “good” temperature readings, if the objective is propaganda spreading headlines.
I ask this question: Since 1900, where have the many billions of pounds of rubber particles and dust gone from the wear and tear of tires gone? The short simple answer is: Anywhere and everywhere! Then there are particles and dust from asphalt road surfaces. There is brown dust from brakes.
Since there is little rain in Palm Springs, home owners should routinely wash this black dust of the roofs of their houses.
How much of these particles and dust end up in the oceans?
Many years ago I read that supposedly there are some sort of microbes or fungus along roadsides that eat the rubber. I have no idea where I read it or if it was disproved.
Modern rubber contains anti-microbial, anti-fungal, anti-oxidant compounds and UV protectants. I once read that the EPA was investigating if these compounds could leach out the rubber, enter water, and harm fish.
Most of what does not circulate in the air is eventually washed into the oceans.
Many cities have storm sewers, and the rain would wash rubber particles into the rivers whose waters eventually flow into the oceans. However, there are a great many highways that are not near rivers so the rubber particles would accumulate in the countryside.
Congratulations to Trump!
Is this change helpful? The UHI is mainly about raising Tavg, not Tmax, because the concrete etc environment retains heat from the day and raises Tmin, and thus Tavg. Does this mean Spencer’s new series will hide the UHI?
I do believe the warmer air arising from all the urban “factors” (hot asphalt & concrete, air conditioning exhausts, waste heat from manufacturing/warehouse/distribution machinery, warm exhausts from vehicular traffic, increased solar absorptivity of buildings compared to natural foliage, etc.) would apply during daylight hours so as to also increase Tmax.
I do not understand your logic that UHI would only affect Tmin, and thus be the only reason for an increase in Tavg.
I am not sure that “impervious surfaces” is the relevant property. You might consider surfaces with high thermal diffusivity? High thermal diffusivity means that heat is readily conducted down into the soil and back out of it again and such surfaces also hold more heat than, for example, loose soil. Lack of vegetation reduces evaporative cooling but in the absence of vegetation, sandy surfaces tend to be self mulching and in dry climates probably don’t evaporate much from their surfaces anyway.
All good points so why don’t we just homogenize it and call it (bond) albedo?
/sarc
Sand surfaces in the Sun, discourage bare feet plodding.
What you are saying is that we don’t understand, of maybe even know, all of the individual phenomena that affect the weather, or our measurements of the weather. Without better knowledge and understanding of these phenomena, and their interactions, all the supercomputer calculations in the world are utterly worthless.
What is being done in “climate science” is a complete corruption of science and engineering.
And there it is in a nutshell. Most of the instrument sites were never intended for, and are unfit for the purpose of, monitoring changes to the climate.
A building is a 3 dimensional surface which is much larger (>> 5x) of its foundation footprint. That should be part of the analysis.
Lots of water being pump onto golf courses etc. I wonder if the water vapor isn’t trapping some heat
For the site in this article and probably for most airports, the max temp would possibly be more influenced by the jet exhaust of both arriving and departing aircraft.
There are two gates aligned in the direction of the temp station. How could they not affect the max readings?
This has been pointed out in many articles on this and other sites. Considering UHI only from the increase in buildings/infrastructure would seem to be pointless when aircraft exhausts, air conditioners, etc are close to the recorders and would cause large temperatures spikes rather than the more gradual increase over time by infrastructure UHI.
This issue does need to be promulgated as often as possible though in order to slay the ‘we are all doomed’ monster
An excellent article from Dr. Spencer!
One significant point not mentioned in his article is that, in addition to the well-described UHI effect on the Palm Srings ASOS site, there is the likely direct warming effect on the station’s measured temperatures from the exhaust plumes from commercial jets as they move along the airport’s taxiways and tarmac (revealed by the dark asphalt lanes/areas in the top photo) and as they move into the gates of the terminal located WNW of the station.
In fact, the Palm Spring ASOS site is located only about 700 feet along the jet engine exhaust vector that a large commercial jet would produce when taxing into a gate that is shown (empty in the top photo) at the SE edge of the terminal.
Prevailing surface winds can also cause the horizontal displacement of jet exhausts issuing in various directions at the airport so as to potentially impact the ASOS location.
It would be very interesting to know if the ASOS temperature sampling rate is sufficiently fast to detect the perturbations from impacting jet engine exhaust plumes (likely with a sampling rate of once per minute, or alternatively an averaging-time of a individual measurement being for less than one minute), where they would be expected to appear as anomalous “spikes” in the string of recorded temperature measurements. That would be further confirmation that the Palm Springs ASOS site data is just garbage . . . and depending on the station’s data processing method might even be found to be the root cause of this station being a 3–5 °F higher “outlier” compared to surrounding stations, as noted in the article’s graphs and related discussion.