Abstract
Understanding microclimatic changes driven by urbanization is critical in the context of global warming and climate change. This study investigates the land surface temperature (LST), the normalized difference vegetation index (NDVI), and changes in land use types for 10 major cities across seven continents between 2001 and 2021. Utilizing MODIS satellite data processed on the Google Earth Engine (GEE) platform, the analysis focused on yearly median values to examine variations in LST during the day and night, as well as temperature dynamics across different land types, including vegetation and bare land. The global mean LST trend from 2001 to 2021, derived from Terra MODIS MOD11A2 data, was found to be 0.025 °C/year. The analysis of daytime and nighttime (nocturnal) land surface temperature (LST) trends across the ten cities examined in this study reveals notable variations, with most cities exhibiting an increasing trend in LST within urban mosaics. Airports exhibited a mean daytime land surface temperature (LST) that was 2.5 °C higher than surrounding areas, while industrial zones demonstrated an even greater temperature disparity, with an average increase of 2.81 °C. In contrast, cold spots characterized by dense vegetation showed a notable cooling effect, with LST differences reaching −3.7 °C. Similarly, proximity to water bodies contributed to temperature mitigation, as areas near significant water sources recorded lower daytime LST differences, averaging −4.09 °C. A strong negative correlation was found between NDVI and LST, underscoring the cooling effect of vegetation through evapotranspiration and shading. This study provides a comprehensive global perspective on the commonalities of urban temperature dynamics in cities across diverse geographical regions and climates, contributing to a deeper understanding of how urbanization and land use changes influence surface temperatures and climate change.
This recent paper investigates the land surface temperature, a vegetation index and changes in land use types for 10 major cities between 2001 and 2021. Most cities exhibited an increasing trend in surface temperatures.
Temperatures at airports were 2.5 °C higher than surrounding areas and industrial zones were 2.8 °C higher than surrounding areas. Areas with dense vegetation showed a notable cooling effect with temperature difference reaching -3.7 °C. Mexico City’s green spaces are up to 12.1 °C cooler than its urban core. The findings indicate that reductions in vegetation and water bodies are consistently correlated with an increase in day temperatures.
Newly urbanized areas significantly reflected the thermal impacts of replacing natural surfaces with impervious materials, leading to notable warming trends in these regions. In Tokyo and SaoPaulo, despite the absence of a spatial urban expansion (1.0% and 0.9%), both daytime and nighttime urban heat island (UHI) effects have increased over the past 20 years.
h/t to Friends of Science
If you want it warmer then chop down all the trees and industrialise the landscape with wind turbines and solar panels. Then you need less energy to stay warm.
But more energy to stave off the cold.. (when solar does not very much)
Understanding microclimatic changes driven by urbanization
So what exactly constitutes a microclimate?
“A microclimate (or micro-climate) is a local set of atmospheric conditions that differ from those in the surrounding areas,” – Wiki.
Let me take the example of my back garden in urban London. The fence and trellis are ~3 metres in height all the way round its three sides (semi-detached house) and covered in Passion flower, Wisteria etc.
The area of the garden is around 35 M^2. Now my garden is very much sheltered from the wind and it’s usually at least a degree warmer than the street outside.
My question is how deep do we drill regarding microclimate? If I go to the outskirts of London the temperature will plunge several degrees at least.
I find the term microclimate to be useless.
On the scale you define, perhaps it is useless.
On the region or locale basis (the original definition), perhaps as exhibited in the article, it is.
Words matter. Without a proper, agreed to definition, communications is seriously impaired.
So what exactly constitutes a microclimate?
Whatever suits the narrative.
As defined above, it’s a region that differs from the surrounding climate.
For example, if a mountain causes prevailing winds to ascend it and drop an increased amount of rain, in an otherwise arid environment. That could constitute a micro-climate.
The microclimate is NOT just atmospheric differences. It is the entire surrounding environment. Trees, shade, brown grass vs green grass vs concrete, elevation, humidity, air conditioning compressors, airport runways, etc.
Each and every thing you can think of can make the temperature at Point A different than at Point B just a mile away. It’s why Hubbard and Lin found in 2002 that regional adjustments to temperature measurements are not legitimate. Each and every measurement station must be compared to a co-located accurate reference in order to determine any adjustment value. It has to be done on a station-by-station basis. Something climate science just ignores when doing homogenization and infilling. Of course climate science believes all measurement uncertainty is random, Gaussian, and cancels so they don’t care at all.
Don’t know the history of the word microclimate, but ever since vehicles had thermometers these small differences became widely obvious. In a section on “Local Pertubations” in the chapter on “The Earth’s Physical Environment,” Pianka, 1988 (4th edition), Evolutionary Ecology, the discussion is on more major habitats like deserts and their components. Although they have an evolutionary explanation, only the major limiting factor water is mentioned for the greenhouse effect, basic biology and ecological research urgent for survival, observations needed for models, carbon dioxide for photosynthesis, and climates seasonal and geographic.
Simple concepts for complex problems used to be taught before the discovery of ‘attritbution science.’
Even in my small plot there are sunny bits and shady bits – differing temperatures on a very micro scale.
There are hundreds if not thousands of different climates in localities all around the world.
So yes, terming an identified climatic locality as having a “micro” climate is fairly meaningless.
What about just referring to the climatic conditions that have been observed to prevail in say Lat 46 N to Lat 52 N X Long 124W to Long 128 W?
Just another identified climatic area that has its own idiosyncracies.
So, global is just bolleaux
Yep.
It is why variance and uncertainties are so important. As you add more and more points together the uncertainty also adds to the point you certainly can’t justify decimal temperature values and may not even units digits.
Climate science wants to call the SEM the measurement uncertainty because it gets so small. It is only an interval where the mean lies when measuring the same thing under repeatability conditions and when the distribution is Gaussian.
Pull a bolt out of a bin of 100. Do you want to know the mean and SEM, or do you want to know the standard deviation which gives the dispersion of the measurements around the mean?
Sshshshsh…don’t say that too loud. You’ll have AlanJ chiming in telling you your wrong and you can get whatever precision you want just by doing the calculation and taking the precision to as many decimal points as your calculator or spreadsheet can handle.
Microclimate contributes to the measurement uncertainty of temperature measurement devices. Does the temperature difference in your garden and the street change in winter when the garden flora dies off?
What you just described is *exactly* why homogenization and infilling between locations ADDS to measurement uncertainty. It just spreads the measurement uncertainty of the reference measurement locations to other locations. And when you average them *all* of the measurement uncertainty from the data elements adds, including those whose measurements were “guessed* at by using values from somewhere else.
Microclimate definition from “Climate Canada” 2nd Edition Hare&Thomas 1979…page 14:
There is an even finer scale of climatic events and processes, for which we use two words. The microclimate is the word used to describe the climate near the ground (Rudolf Geiger’s term for it). It concerns the differences along the vertical at a given site-the temperature difference between instrument screen level and soil surface, for example, or even between upper and lower leaf surfaces.
These differences may be large and important, so it is good to have a word for them. For the small horizontal scale of climate, such as the difference between one field and the next, or between one side of a smal valley and the other, we use Warren Thornthwaite’s term the topoclimate.
So one take-away would be that if you’re concerned about your environment inexorably warming up, move to a cooler one nearby.
But don’t make the same nest you had before.
Because doing the same thing over and over and expecting a different outcome is the definition of –
well you know the rest . . .
One cannot model a single molecule in a 25km^2 grid.
One cannot model a global climate in a 25km^2 grid with any fidelity.
This type of analysis is a dose of reality.
Well done.
Story tip Gone with the wind
In a latest blow to Red Ed’s net zero crusade, Britain’s biggest power generator has warned that falling wind speeds are driving up energy bills – and that’s unlikely to change anytime soon. RWE, which supplies around 15% of the UK’s electricity and increasingly relies on wind power said:
The Intergovernmental Panel on Climate Change forecasts that global winds will continue to slow in the decades ahead.
https://order-order.com/2025/08/14/blow-to-miliband-as-britains-biggest-power-generator-warns-low-wind-driving-up-energy-bills/
Have they blamed CO2 for slowing global winds yet?
how many of those cities got smaller over the interval?
Partially from urban effects, and partly from the effects of two major El Nino events.
Don’t forget Hong Kong!
Study: UHI in Hong Kong accounts for most ‘warming’ since 1970 – Watts Up With That?
This study starts with Median LST, then moves to mean trend variations. Is this a reasonable shift for comparison? Do the trends have a normal distribution?
While this study is for surface skin temperature, which will be magnified compared to air temperature, what’s interesting is that got pretty substantial warming trends over a recent 20 year period. In our recent paper where we used population density as a proxy for urbanization, there was very little UHI warming since the 1960s or 1970s… but population density is not the best measure of urbanization, since you can have a stable population but continued growth in the number of stores, parking lots, etc., as wealth increases. So, this suggests UHI warming is continuing to cause the cities (where most people live) to warm faster than the rural surroundings.
What is your view of the fact the ‘pristine’ USCRN data are currently warming faster than the adjusted ClimDiv data?
Doesn’t this confirm that warming is occurring independently of UHI?
Even Anthony Watts no longer denies the world is warming
Yeah, very rarely now do you see a post denying warming. Contrast with this site 10-years ago.
(The odd wingnut screed pasted from NoTrickZone and the usual diehard tinfoil-hat-clad commenters excepted.)
Where has he said such claim, or you are just making it up…….
Warming matters? UAH data show step changes suspiciously coinciding with natural phenomenon such as volcanic eruptions, natural Super El Niño events by some 5 months later, and the still recent Hunga Tonga eruption spewing water vapor into the stratosphere. Nature itself denies much measured room for AGW.
Similarly, the degree of warming matters. In Spencer and Cristy’s paper a few years back measured 12 scorn belt states surface temps against climate models for 50 years time (1973-2023, IIRC).
the models ranged uselessly for prediction 0.2 to 0.9C degrees.
But the officially measured temperatures were found just above one-tenth a degree!
Thus the Alarmists Hysteria is PROVED right — 0.2C plus degrees is going to fry the earth and kill off all life!