Trees found to reduce land surface area temperatures in cities up to 12°C
A team of researchers with the Institute for Atmospheric and Climate Science, ETH Zurich, has found evidence that indicates that stands of trees can reduce land surface area temperatures in cities up to 12°C.
In their paper published in the journal Nature Communications, the group describes how they analyzed satellite imagery for hundreds of cities across Europe and what they learned.
Prior research has suggested that adding green spaces to cities can help reduce high air temperatures during the warm months—cities are typically hotter than surrounding areas due to the huge expanses of asphalt and cement that absorb heat.
In this new effort, the researchers looked at possible temperature impacts on land surface areas instead of air temperatures.
Such temperatures are not felt as keenly as air temperatures by people in the vicinity because it is below their feet rather than surrounding them.
The work by the team involved analyzing data from satellites equipped with land surface temperature sensors.
In all, the researchers poured over data from 293 cities across Europe, comparing land surface temperatures in parts of cities that were covered with trees with similar nearby urban areas that were not covered with trees.
For comparison purposes, they did the same for rural settings covered in pastures and farmland.
They found urban areas with trees typically had land surface temperatures that were two to four times cooler than similar areas nearby that had no tree cover.
Such differences translated to approximately 0 to 4 K lower than surrounding areas in parts of Southern Europe—in other regions, such as Central Europe, the differences were as high as 8 to 12 K.
Interestingly, the researchers found no such differences in rural areas. And they found no differences for other types of vegetation in the cities.
The researchers note that trees are able keep the ground cooler due to the shade they provide, which suggests they help reduce building surface temperatures in similar ways.
Their work highlights the impact that adding tree cover to urban areas can have.
See more here: phys.org
Header image: Gardening KnowHow
Editor’s note: I am surprised these ‘researchers’ have only just discovered that trees shading the ground keeps the ground cooler than if it was in direct sunlight. I learned that in the Cub Scouts 50 years ago.
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very old white guy
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Must have taken a lot of research. One of my homes over the years had beautiful mature trees surrounding it. On a hot day one could feel the temperature difference just walking under them. I wonder what that stunning research cost?
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Andy
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Whatever it cost it was too much.
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Jerry Krausej
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Hi Andy and Very Old White Guy,,
Andy, how stupid are you??? I do not have to guess! Very Old White Guy makes a important fundamental SCIENTIFIC observation and you make your nonsensical comment.
What I add to Very Old White Guy’s comment is that the the trees which shade the ground during day in the summer also converts a portion of the solar’s radiation into stored plant matter.energy which doesn’t happen on planets which have no trees or other plants.
Good job; Very Old White Guy!!! As USUAL!!!
Have a good day, Jerry
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Andy
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I am shocked at the arrogance you displayed here. I make a perfectly reasonable comment, and you insult me. What exactly is your problem?
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Jerry Krause
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Hi Alan and PSI Readers,
You state (write): “I make a perfectly reasonable comment,” This is only your opinion!!! Can I, or other PSI Readers, have a different opinion???
Have a good day, Jerry
Andy
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Of course you can, but without including an insult.
Jerry Krause
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Hi Andy and PSI Readers,
It is SO easy to overlook the OBVIOUS!!! With the result that I have made many mistakes.
John O’Sullivan has taught me that many PSI Readers do not have time, or interests, to read long articles. But take a look at his articles.
Very Old White Guy (VOWG) has mastered compacting information (wisdom?) into quite few words. I comprehend (understand) that his question–“I wonder what that stunning research cost?–was a statement that it costed NOTHING! Hence when you wrote–“Whatever it cost was too much.”–was nonsense because there is nothing less than nothing.
However, what VOWG overlooked was (is) a difference between a qualitative observation and a quantitative observation (measurement). Which quantitative measurement always requires an instrument. And instruments always cost something. I do not consider myself to be ARROGANT (highly intelligent) to recognize this difference. I have only learned TO TRY TO NOT OVERLOOK THE OBVIOUS. Which I know that I too often fail to do!!!
Have a good day, Jerry
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MattH
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Hi Very Naughty Very Old White Guy (Jerry) and readers.
Jerry is correct. The tree/temperature research clearly supports the urban heat island effect and therefore urban weather stations showing climate temperature rise doom in an artificial and incorrect manner.
Good on yuh Jerry.
Matt
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Jerry Krause
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Hi PSI Readers,
Since I have called attention to possibly overlooked observations, consider the fact that Richard Feynman wrote (“What Do You Care What Other People Think?”) about his investigation of the Challenger accident.
First I read: “We also heard about the low temperatures before the launch from a man named Charlie Stevenson, who was in charge of the ice crew. He said the temperature had gone down to 22 degrees [F] during the night, but his crew got readings as low as 8 degrees at some places on the launch pad, and they couldn’t understand why.”
Then, about four pages later Feynman wrote: “NASA had a theoretical calculation of how the temperatures should vary around the launch pad: they should have been more uniform, and higher. Somebody thought that heat radiating to the clear sky had something to do with it. But, then someone else noticed that BK’s reading for the slush was much lower than the photograph indicated: at 8 degrees the slush—even with antifreeze in it—should have been frozen solid.”
And Feynman reported that these temperatures were being measured with an ‘infrared scanning gun’ (IR Thermometer). The accident occurred January 28, 1986 when the early, now common, IR Thermometer, had been designed, constructed, and was maybe being used by NASA, for the first time to measure temperatures. For both NASA and Feynman knew the IR radiation flux being emitted from the surfaces of matter was according to the experimental Radiation Laws which defined the magnitude of the radiation flux relative to the matter’s temperature.
Now, there are those who claim that Surface Temperatures cannot be measured with any device These people overlook the fact that there would be no experimental radiation laws if there were no such device. For a Scientific Law is not a theory, it is a generalization of reproducible experimental results. But we should recognize that both NASA and Feynman, after the accident in January 1986, seemed unaware that 8 degrees was not the temperature of the BULK slush and that it was instead only that of its SURFACE.
To keep this comment brief I stop here. In a day or so I will continue to describe a simple fact that I, a chemist, claim to have seen long ago with my mind’s eye (imagination).
Have a good day, Jerry
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richard
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2011 – https://wattsupwiththat.com/2011/09/16/water-evaporated-from-trees-cools-global-climate/
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Jerry Krause
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Hi Richard,
What you draw our attention to is an observed fact. However, I call attention to the fact that a tree’s roots go down into the ground and that is where it gets its water to evaporate (transpire). But I have read that in the Shara Desert there are brine pools, in which shrimp live, that are cooled by evaporation without the factor of plants. For underground water is lifted to the surface by underground water at a higher location. Which plentiful water, necessary for LIFE of any kind, seems missing in (on) the other planets of our solar system. The Earth is a very unique place.
Have a good day, Jerry
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Alan
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Isn’t this the wrong way round? It is the city infrastructure that are increasing temperatures above that found in nature.
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Jerry Krause
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Hi Alan,
Interesting comment!!!..Less someone jumps on the wagon and conclude that cities cause Global Warming, I draw attention to what I believe is an accurate observation. One does not need to go many miles outside of the cities to find the natural temperatures of the earth’s atmosphere and surface. Which NATURAL temperatures can vary widely between a relatively short distances. The earth is quite heterogeneous and there is nothing that can be said to be average in time and space.
Have a good day, Jerry
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richard
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Here is that 12C figure again –
2014- “There’s a good reason why city dwellers flee to the countryside to cool off in the heat of summer: Rural areas are usually not as hot. Because of the “urban heat island” effect, cities of a million or more people can be 1–3°C (1.8–5.4°F) warmer on average—and as much as 12°C (22°F) warmer in the evening—than the surrounding area, according to the U.S. Environmental Protection Agency”
https://www.smithsonianmag.com/science-nature/city-hotter-countryside-urban-heat-island-science-180951985/
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Jerry Krause
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Hi Alan, Andy, Richard, and PSI Readers,
I have to regularly admit to the mistakes I regularly make here at PSI. So, Alan, please excuse me for crediting you for what Andy wrote.
Now, I admit that previously I had only read the title of this article and the two comments that I had read. Now that I have read the article, I find I can agree fully with what was written.
However, I suspect, but do not absolutely know, that these scientists are unaware of the data being measured and reported at this link (https://www1.ncdc.noaa.gov/pub/data/uscrn/products/hourly02/). So they probably do not know that the surface temperature of whatever beneath an IR thermometer pointed downward from about 1.5 meter above the ground has been measured and reported hourly for many locations.
So these scientists likely do not know that routinely the temperature difference between the measured surface temperature and the air temperature being measured 1.5 meter above the surface can be far greater than 12C near midday given a cloudless atmosphere.
Now, fact is that I have been urging PSI Readers to take a look at the data being measured and reported by various international research projects of which the previous link is one And the only evidence, of which I am aware, that any PSI Reader has actually read what I have written, are comments that a surface temperature ncannot be measured by a IR Thermometer.
I have read many articles and comments about the 2nd Law of thermodynamics here at PSI; so I know that many here are aware that a heat engine requires a TEMPERATURE DIFFERENCE to produce actual WORK. Which temperature difference has been noted is created by a shadow on the ground surface during midday.
Thank you all very much for the artcle and comments because they I have provided the context for what I have just simply shared.
Have a good day, Jerry
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