Category: Daily News

Urban Microclimates: Surface Temperature Trends Measured Across Ten Major Cities

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


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August 14, 2025 at 08:06AM

REAL ELECTRICITY PRICES – FROM GAS OR RENEWABLES

This data tool from a left wing, pro-renewable think tank is updated daily and allows you to calculate electricity pricing across Europe.

What makes this EMBER tool so valuable is that it is authoritative and can be simply wheeled out every time the renewable lobby claims that wind power costing £117/MWh is somehow cheaper than gas.

EMBER Electricity Price Data Tool | NOT A LOT OF PEOPLE KNOW THAT

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August 14, 2025 at 06:06AM

CFACT helps protect Lava Ridge, Idaho from big wind

CFACT’s Conservation Country report put saving Lava Ridge on the radar.

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August 14, 2025 at 05:23AM

WYE Addendum – a detailed look at what the actual data tells us.

I recently reviewed the now closed but historic weather station at Wye Agricultural College in Kent. All the evidence showed this site to be in a very good location. This location had not changed throughout its long history and the site had been very well maintained in its operational life. Its observations record was excellent with very, very rarely a missed day. Perhaps equally importantly there had been no instrument type changes over its lifetime. This deserved detailed analysis as such a quality site would represent a large inland area of the county of Kent. Here are the initial findings.

Firstly I am deeply indebted to former professional auditor Dave Woolcock for his extensive and diligent work on this. Dave has downloaded from the official CEDA files all the detailed temperature records for EVERY weather station (open and closed) that exists on their database. He compiled both running maximum and minimum temperature averages from the archived 17,210 days ( i.e. 34,420 readings) available. His full methodology (in his own inimitable straight forward style) is included at the end of this post but his basic precis is:

“Dead short version. Read and combine the CEDA csv file data into a sorted XL file (the data is all DLY3208 so one day per row). Compute 12-month moving average for tmin and tmax using @Average of the previous 365 days. Plot using XL charts”

{DLY 3208 is the daily logging system used by the Met Office. Manual stations supply one timed set of readings per day at 09:00 GMT}

Average Maximum.

Average Minimum

I would like to re-emphasize this is not a cherry pick. Wye simply represents the first long term operational site that I could establish meeting the following criteria:

  1. CIMO Class 1 or 2 Site.
  2. Not relocated over data reporting period.
  3. Identified good maintenance with no significant change of surrounding conditions.
  4. Not subject to significant Urban Heat Island effects.
  5. No instrumentation changes (i.e. from LIGT to PRT)
  6. Consistent good quality observations record. (WYE was excellent)

I leave it to readers to draw their own conclusions from the above representation.

I stress that all this data comes solely from the MET Office themselves and is readily verifiable from the CEDA link given above. Photocopied manual records from 1924 to 1958 exist for this site (in Fahrenheit) on the Met Office files here.

https://digital.nmla.metoffice.gov.uk/SO_13c674e7-a2fc-4263-9283-e76a1c8ccc63/

I will transcribe these myself in order to reconstruct the preceding 34 years in due course though this will be a somewhat laborious process.

I would very much appreciate as many readers views and comments as possible on this (good or bad) to assist moving the Surface Stations Project beyond just the weather station site review phase and into a new national historic temperature reconstruction.

And now for the important bit: Courtesy of the much appreciated Dave Woolcock.

——————————————————————————————————————-

METHODOLOGY

1. Scoop data for Wye from CEDA csv files and accumulate into a single XL sheet sorted into date order

2. Highlight all the data in the tmax column and Insert / Chart (line graph)

3. Pick light orange colour, set line width to .25pts, change the x-axis labels to pick up the date column and move Labels to “low” position.

4. Add a MA column (H) by scrolling down a year and averaging the first year.  Copy down to the end. Do same for tmin in column I by copying the formula across and down.

5. Return to graph and add in another data range – column H

6 twiddle colours and line width to look good, add in chart title. Save to PNG file. 

7 copy / duplicate the entire chart below and edit it. Change data ranges to point to tmin and the tmin moving average. Change colours to cool blue. Save chart to PNG file.

8 the data is “as is” not adjusted for throwback so for each given day tmax and tmin will be out of sync compared to true MO practice. But for this exercise it doesn’t matter. If it did we could just shift tmin down a row.  If the data were based on 12-hour readings we would need a lot more data prep before we could plot it.

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August 14, 2025 at 05:16AM