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UHI May Account For Half Of Climate Warming In China

July 21, 2019

By Paul Homewood



A new study by Nicola Scafetta shows that a considerable percentage of China’s global warming from 1940 to today is due to the phenomenon of urbanization. However, the models mistakenly associated this same warming to anthropogenic forcing:





Near-surface temperature records show that China warmed by about 0.8 °C from 1950 to 2010. However, there exists an ongoing debate about whether this warming might have been partially due to urbanization bias. In fact, homogenization approaches may be inefficient in densely populated provinces that have experienced a significant urban development since the 1940s. This paper aims to complement previous research on the topic by showing that an alternative approach based on the analysis of the divergence between the minimum (Tmin) and maximum (Tmax) near-surface temperature records since the 1940s could be useful to clarify the issue because urban heat island (UHI) effects stress the warming of nocturnal temperatures more than the diurnal ones. Then, the significance of the divergence observed in the data could be evaluated against the expectations produced by the CMIP5 general circulation model simulations. From 1945–1954 to 2005–2014, on average and over China, these models predict that Tmin had to warm 0.19 ± 0.06 °C more than Tmax. However, during the same period, the climatic records show that Tmin warmed 0.83 ± 0.15 °C more than Tmax. A similar analysis demonstrates that the effect is more pronounced during the colder months from November–April than during the warmer ones from May to October. A comparison versus China urbanization records demonstrates that the regions characterized by a large Tmin-Tmax divergence are also the most densely populated ones, such as north-east China, that have experienced a diffused and fast urbanization since the 1940s. The results are significant and may indicate the presence of a substantial uncorrected urbanization bias in the Chinese climate records. Under the hypothesis that Tmax is a better metric for studying climatic changes than Tmean or Tmin, we conclude that about 50% of the recorded warming of China since the 1940s could be due to uncorrected urbanization bias. In addition, we also find that the Tmax record from May to October over China shows the 1940s and the 2000s equally warm, in contrast to the 1 °C warming predicted by the CMIP5 models.

  1. markl permalink
    July 21, 2019 5:42 pm

    UHI is the only measurable component of AGW.

    • Charles Wardrop permalink
      July 21, 2019 5:52 pm

      Markl: thankyou! Very illuminating, makes total sense, much more convincing than CO2etc.effects.

    • Tim Crome permalink
      July 25, 2019 10:32 am

      It was considered so important that the EU had a separate project related to UHI, it appears to have been closed about 5 years ago. Ref.:

      I suspect that it’s not only in China that UHI pollutes the temperature records. Combined with the other known warming adjustments it’s probably reasonable to conclude that we’re well into a cooling cycle!

  2. July 21, 2019 6:04 pm

    The most populated regions of China are near the coast, a complicating factor in determining causes. To be convincing the study needs to compare densely and lightly populated regions with similar geography.

    • markl permalink
      July 21, 2019 6:57 pm

      Not that complicated. All you need to do is compare near temperatures within boundaries.

  3. July 21, 2019 7:25 pm

    Reblogged this on Climate- Science.

  4. Athelstan. permalink
    July 21, 2019 7:27 pm

    Fixing data sets = globull warbling, just ask NOAA, GISS, HadCRUt.


    Step right this way for the freak show, the british Bullsh*7 corp’ and mates, the climastrology posse, aka the met office, on extended extra promulgation, alarmist propaganda this week, #morethan and hottest evah – again!

    Yet, we predict, there’ll be no account taken, sorry admitted concerning, the regional London Heat Island effect, oh and airport jet engines and tarmac neither.

  5. Gamecock permalink
    July 21, 2019 7:46 pm

    ‘China’s global warming’


  6. It doesn't add up... permalink
    July 21, 2019 9:24 pm

    China didn’t really use much energy until quite recently. Its growth has been very rapid since the mid 1990s. Does this signal agree with the history of energy use?

  7. July 21, 2019 11:11 pm

    Reblogged this on Tallbloke's Talkshop and commented:
    Whether the urban heat island effect is in fact warming ‘the climate’ is debatable, but in a propaganda war it can be made to seem so. In any case this needs as wide a coverage as possible, to offset at least some of the alarmist spin about supposed man-made warming that’s pushed down everyone’s throats on a daily basis.

    • Up2snuff permalink
      July 22, 2019 6:48 pm

      oldbrew, I think it must do. Along with population increase and the ubiquity of electric and ICE motors everywhere and in everything, it is one of five factors occurring pretty much exclusively in the 20th century with the major growth in numbers coming after WW2. The other one of the five, tungsten light bulbs, are being done away with.

      It is interesting that some Global Warming & Climate Change proponents – worried about an actual lack of temperature increase – are now starting to to dispense with the word ‘Global’. A person that I contend with occasionally, says that it doesn’t matter that the global temperature has not increased significantly. It is local increases that are important.

      I thought, funny. Funny, I thought. I thought we were told that the 97% of world scientists all agree and are far cleverer than we are but somehow they don’t know what ‘Global’ means and how to use the word in reporting their research.

  8. Bruce of Newcastle permalink
    July 22, 2019 12:37 am

    UHI may have caused almost all the recent warming globally. Roy Spencer’s paired-station data shows that land use changes cause one degree C of warming with only 60 people per square km.

    The Global Average Urban Heat Island Effect in 2000 Estimated from Station Temperatures and Population Density Data (2010)

    See especially the last graph in the study.

    The rise in population worldwide, especially in the last 50 years, would have a massive UHI effect based on this data.

  9. Broadlands permalink
    July 22, 2019 1:09 am

    Cherry blossoms as indicators. “Just as warming March temperatures are likely to blame for the earlier bloom dates in Kyoto, the same holds true in Washington. Since 1921, Washington’s March temperatures have warmed at the rate of about 2.8 degrees per 100 years. In both Kyoto and Washington, the warming trends and earlier blooms are most likely due to a growing urban heat island effect and increasing concentrations of greenhouse gases in the atmosphere.”

    Most likely the UHI effect and NOT our added CO2. According to NOAA, since 1921 Al Gore’s home state of Tennessee has never been warmer….. Same is true for Kentucky and Mississippi, Louisiana, Alabama and West Virginia…NOAA.

    • tom0mason permalink
      July 22, 2019 9:33 am

      Of course Al Gore and co. will ignore the dust-bowl years of the 1930, and that 1936 was THE hottest year in the USA.

  10. tom0mason permalink
    July 22, 2019 9:15 am

    “UHI May Account For Half Of Climate Warming In China”
    And nearly all the rest of the variation is cause by variation in cloud cover, see —

    Click to access acp-13-8505-2013.pdf

  11. swan101 permalink
    July 22, 2019 11:54 am

    Reblogged this on ECO-ENERGY DATABASE.

  12. July 22, 2019 1:20 pm

    Another climate classic today: Animals’ body sizes shrinking from climate change, study finds
    by University of Cape Town

  13. Gerry, England permalink
    July 22, 2019 1:51 pm

    Now there’s a surprise, especially if you are a climate ‘scientist’.

  14. Nordisch-geo-climber permalink
    July 22, 2019 2:09 pm

    London, Houston, no surprise UHI effect when you look at all the concrete, warehousing (usually Amazon) and increased population and transportation.

    • Up2snuff permalink
      July 22, 2019 6:51 pm

      Nordisch, if the reports were true, some people got a bit of a local UHI surprise when bits of their cars melted in central London a couple of years back.

  15. July 23, 2019 12:10 am

    Reblogged this on Climate Collections.

  16. July 27, 2019 10:04 pm

    Half of my childhood I grew up in a small village about 60 km north of Vienna. Most of my bigger family lived in or close to Vienna and my father delivered his produce once a week to his biggest customer. I had many opportunities to come with him. I learned one thing pretty quick. When there was snow where we lived, this did not mean that it would be snowy in Vienna. The darker city with all its tarmac and darker buildings was a heat island and when we went on the small mountains on the fringes of the city, this effect could be seen pretty nicely. An otherwise white flatland to the east with Vienna snowless or significantly less white – even in open spaces. This was more than 40 years ago and at the time we were told that we would freeze to death but the effect of the urban heat island did not need explanation – it was common sense. Not today it seems.

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