Guest Post by Willis Eschenbach
[OK, had to start over, had bad numbers for the areas. Graphics have been replaced. I was using “core area” but I should have been using “greater metropolitan area”. All conclusions are unchanged.]
I got to thinking about the phenomenon known as the “Urban Heat Island” effect, or UHI. Cities tend to trap heat due to the amount of black pavement and concrete sidewalks, the narrow canyons between buildings that slow down the wind, and the sides of the buildings reflecting sunlight downwards.
As a result, cities are often warmer than the surrounding countryside. In some cities, it’s hot enough that it affects the local weather. Here’s a simplified diagram:
What I was curious about, however, was another kind of urban heat effect. This is the heat from all of the energy used within the city—electricity, fuel for transport, fuel for heating buildings, all of it. Eventually, almost all energy ends up as heat. So I went and got the energy usage for 27 huge “megacities”, along with the area of the city itself. I then combined the two to give me a measure of citywide energy usage in watts per square metre (W/m2). As a measure for comparison with Figure 2 below, a doubling of CO2 is said to increase the “forcing”, the total radiant energy impinging on the surface, by 3.7 W/m2.
This was surprising to me. I hadn’t expected the effect to be so large.
Finally, I converted the forcing to an equivalent warming. The Intergovernmental Panel on Climate Change (IPCC) fifth assessment report, completed in 2014, gave a likely “Transient Climate Response” of about 1°C to 2.5°C for each additional 3.7 W/m2 of forcing. I’ve used 1.5°C because the heat generation persists over time. As a result, the cities have had time to equilibrate to the additional heating. Figure 3 shows that result.
Not much more to say about all of that. Note that this is a “first cut” analysis, I make no overarching claims about the accuracy of the results. I’ve used conservative assumptions and the best data I could find. It looks to be a significant additional heating source due to direct energy usage in the densest of the largest cities, one that is not generally included in the calculations of the Urban Heat Island.
Here, I’m in the Forest Cool Island, life is good. I spent my morning crawling around under my house successfully putting a new “generator” into my floor furnace so we now have a warm house again, a less than pleasant job that came complete with a veritable plethora of bad words. Then I got out the pumice stone and scrubbed a toilet bowl until it sparkled, and this has been my afternoon project … do I know how to have fun, or what?
My very best wishes to each of you,
w.
[UPDATE] In the comments below, someone asked about human body heat and how that affects the forcing in megacities. Humans on average put out on the order of 120 watts continuously. Here’s how that plays out.
You can see how densely populated Seoul, South Korea is …
DATA: I’ve appended the data below, in comma-delimited form. PJ is petajoules, 10^15 joules.
City, PJ, km2,Population Beijing, 952, 6562, 21516000 Buenos Aires, 702, 10888, 3054000 Cairo, 282, 1600, 10230000 Delhi, 316, 3182, 11034000 Dhaka, 350, 1353, 8906000 Guangzhou, 1474, 7711, 14043000 Istanbul, 464, 5500, 14025000 Jakarta, 589, 5100, 10075000 Karachi, 339, 1100, 14910000 Kolkata, 78, 1785, 4486000 Lagos, 350, 1535, 861000 London, 1065, 11391, 8825000 Los Angeles, 1848, 10780, 3884000 Manila, 918, 2521, 1780000 Mexico City, 1099, 7346, 9041000 Moscow, 1984, 14925, 12197000 Mumbai, 191, 2350, 12478000 New York, 2824, 17884, 8622000 Osaka, 1258, 6930, 2691000 Paris, 657, 17174, 2229000 Rio De Janeiro, 384, 4540, 6718000 Sao Paulo, 589, 8479, 12252000 Seoul, 1848, 5076, 10197000 Shanghai, 1644, 5177, 24256000 Shenzhen, 350, 3051, 8378000 Tehran, 1145, 9500, 8154000 Tokyo, 2438, 8014, 13839000
Willis, please don’t forget that cities collect, funnel and channel rainwater away, preventing much of the surface heat from evaporating water that in would have otherwise evaporated, switching off much convective transfer by water, and generally drying the area, setting a preference over the storm-drainage parts of urban areas, for energy transfer by direct radiation over transfers by convection and the potential energy held in water vapor (which is released later during condensation). And I now notice that Robert of Texas just made this same point.
Some of these mega cities are also subsiding under their own weight.
http://harvardpolitics.com/world/jakarta-sinking-how-subsidence-endangers-indonesias-capital/
The underlying cause of Manila’s problem is unchecked usage of water from groundwater sources.
https://www.bangkokpost.com/world/1740904/sinking-cities
Just to re-emphasise the statement in the article you posted that much of the effect is to do with the extraction of groundwater too. Rest of the article is the usual B/S.
Notice that it is axiomatic when we are told from On High, by our Wise Superiors that High Density STACK -N-PACK is “The Future”, that it is “Most Efficient” and “Better for The Environment”…. that THEY always keep their second homes, vacation homes and cabins well outside the Urban crab-buckets that they prescribe for the rest of us…
“Urban crab-buckets”
LMAO – I love that “visual.”
Headline “The Megacities Are Cooking” should read “The Megacities Are Cooking with microwaves”
“Electrosmog” describes the electromagnetic waves surrounding us in our environment. According to NASA [1]:
“As you sit watching TV, not only are there visible light waves from the TV striking your eyes, but also radio waves, transmitting from a nearby station, and microwaves carrying cellphone calls and text messages, and waves from your neighbor’s WiFi, and GPS units in the cars driving by. There is a chaos of waves from all across the spectrum passing through your room right now.”
Every year, the quantity and nature of radio and microwaves contained in this Electrosmog increases. However, research into whether they might interact with human biology, and exactly how they might interact, is a field clouded by the jargon and complexity of each technology and hampered by inadequate experimental guidelines.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5406447/
Not to mention the radiation from your microwave oven as you warm up your TV dinner.
In 2003-05 Seoul tore up one of its highways running through the city and restored the Cheonggye Stream.
The immediate surrounds of the stream are up to 3C cooler than the neighbouring built-up area.
https://www.researchgate.net/publication/237210817_Changes_of_the_micro-climate_and_building_cooling_load_due_to_the_green_effect_of_a_restored_stream_in_Seoul_Korea
https://seoulsolution.kr/en/content/3519
yes it’s a beautiful area.
Imagine cool zones in cities.
Now who would have thought that cities could have cool islands?
Science of course.
Here is another way of coming at it, which gives a slightly improbable answer, so suggestions for refinement welcome. (Decane used as a handy example hydrocarbon.)
Taking London as example. (Data from wiki.)
Population density (people/m2): 0.0057
Per capita CO2 emissions (UK, t CO2/person): 5.6
Per capita C emissions (t C/person): 1.53
Expressed as moles of decane (divide mass in grammes by 12): 12727
Combustion enthalpy decane: -6778 kJ mol-1
kJ/person/year: 86,300,000
kW/person: 2.73
kW/square metre: 0.015
W/square metre: 15
Expressed as doublings CO2 (divide by 3.7): 4.2
Temperature increase locally (1.5 C/doubling): 6.3 C
Pleased to receive opinions on getting a better number. I suppose an obvious point is that not all the carbon footprint comes from within the city.
j
Someone up above commented on the energy in the food eaten by the population … humans on general emit an average of about 120 watts of thermal energy. Here are the results per city, I’ve added this to the top post as well.
w.
Another reason for UHI, and a concept that most climatologists seem to not understand in general, is the increased surface area from buildings and other structures. You see, when you type in a search engine “surface area of Earth”, the number given is an abstract number based on conceptualizing the Earth as a perfectly smooth marble, when in reality we know that is far from true.
The abstract number is the figure used to derive the erroneous +33 C of the Earth’s surface. Using the real surface area would bring the real surface temperature much closer to that estimated. Climatologists should understand elementary concepts before trying to destroy the world’s economy on account of their dogmatic beliefs.
Please note that I had bad data, so I had to recalculate and replace the graphics. Conclusions are unchanged, city rankings are different.
w.
Seem to remember that Leif Svalgaard said that all of our energy usage on Earth, when spread out across the globe, is the same as the energy the Earth gets from the reflection of the Moon. ie: not a lot.
Not sure how true that is.
Ralph
Willis, there is an underground effect, too. After a light snow or frost when the paved streets are white, there will be melted circles above the manhole covers. Room temperature and hot water sewage heats the pipes, ground, manhole shafts, and the cast iron covers. Helpful hint – if your community has paved over manhole covers, this effect allows the public works staff to locate hidden manholes.
In a similar vein, at my last house, the sewer line ran along the foundation underneath the driveway. Always was the last part of the driveway to accumulate frozen precipitation, and the first spot where frozen precipitation melted.
Gives a whole new connotation to the phrase “Hot Shit,” eh? 😀
Interesting analysis Willis. Of course, the impact on global temperature is relatively small since only a small proportion of our planet’s surface has been intensively developed into large cities.
However, the localized effect is, as you have shown, potentially very large.
We also know that a significant proportion of our temperature measuring stations are located in or close to areas of significant human development. So believe the impact of UHI on global temperatures as commonly reported is indeed significant (albeit hard to quantify).
I checked Willis’s LA numbers just for fun. It seems his PetaJoule numbers are annual totals.
1,848,000,000,000,000,000 Joules
÷ 3,600 Joules per watt-hour
÷ 365 days per year
÷ 24 hours per day
÷ 10,780 square kilometers
÷ 1,000,000 square meters per square kilometer
= ~ 5.436 W/m2, as shown in the graph
A similar calculation shows that the average Los Angeleno uses about 11,000 kwh of energy from all sources, which is higher than I’d expect, but certainly plausible given that all commercial and industrial energy consumption is included.
Minor quibble: how do “sides of the buildings reflecting sunlight downwards” trap heat citywide?
Forced additional heating of the concrete/ground. Much like all those mirrors at Ivanpah power station outside of Las Vegas. Reflect some sun on a surface that already gets sun, and you increase the amount of heating of that surface (more power radiated on it).
Thanks, but still not buying the argument. With a building in the way, heat that would have landed on First Street now lands on Second Street. No net change to city’s heat.
You seem to be neglecting the increased surface are of the building vs. a flat piece of ground with no building on it.
Including the roof, which is the same size, give or take, as the “footprint” of the building anyway.
Add the data in figure 2 and 4, take observed values of the urban heat effect, the temperature that is, and you can calculate what the true forcing is, the temperature rise for 1.0W/sqm?
The measurement of rising temperatures in the centre of large cities was an invaluable source for the Warmistas in search of any evidence that CO2 was causing catastrophic heating on the Earth.
To me it seems that the factor used for conversion to temperature change is too high.
I had thought that forcing is the transient imbalance at the top of the atmosphere. To me that suggests that the increased back-radiation at the surface needed to redress the imbalance is greater than that imbalance. So the conversion factor should be lower. No?
“Finally, I converted the forcing to an equivalent warming. “
That would work if the cities have a glass cover. But in fact most of the extra heat is blown away in the wind.
That’s why it’s always warmer in the city, right Nick
If you hunt around the US EPA website and pursue Urban Heat Island effects there is plenty of data to show the expected temperature rises from Willis’ calculations are well below those measured.
There are also lots of built environment effects raising the temperature even more.
Some places are even trying to paint the dark streets white to reduce that.
Do you have any evidence to support that claim?
The fact that UHI is huge and growing is already documented. Don’t ya just hate it when real world data refutes what you are paid to believe?
As someone who rode a Triumph Bonneville back in the 60’s there was definitely a temperature difference as one left the city and went into the suburbs and country. You got colder.
Willis,
Really interesting piece, I know in my CBD suburb you can walk down the street, turn a corner and suddenly get +2C because of the layout. So even within the center of big cities there will be significant effects.
From my understanding, if this is accurate, then it should have serious implications for the temperature homogenisation processes currently being used. Would you agree?
It would also be good to see how this effect scales with city size…
Why just cities. Look at global total energy production and add that to the earth’s heat balance.
One can get a similar result by using total USA energy consumption and allocating that to urbanized area.
Willis,
Since you appreciate constructive criticism : it’s not only under your home you may crawl around and use strong words :
Your numbers for Paris are not consistant : a population of 2,3 million is for the “inner city” which is 105 sq km .
The “greater Paris” reaching as far as you find contiguous buildings is about 2845 sq km and about 12 million people, more or less organized in 412 “communes (boroughs ?). And the whole “région Ile – de – France” grouping 1281 “communes” is only 12000 sq km wide.
All numbers according to the french Larousse encyclopedia.
I hope it will make us parisiens and banlieusards look a li’l bit more like hot peoples…
Keep on surprising and enlightening us !
Cheers !
If this amount of heat is subtracted from the temperature record, little or no warming remains; and, as urban weather stations now comprise most of the data for the average global surface temperature there is a major uncertainty in that as well.
Back about 1950 a paper was published about the down-wind weather from South Bend, IN. By 1950, more than half of all employment was in the manufacturing sector. (Wiki)
The paper was republished in a book of readings used in university ‘urban geography’ classes. On of my instructors knew the authors of the paper and the editors of the book.
This was my first exposure to a study of the effects of cities on local weather.
Nice work, Willis,
This fits comfortably with a boring, lengthy review of UHI that I posted on WUWT a year or so ago. My strong conclusion was that UHI is an effect that probably distorts land surface records unacceptably, but those in paid research that should research and correct it at trying to avoid it. Mostly, Though I did reference a few papers worth reading. Geoff S
wrong. It doesnt.