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ClimateMovie fact check: Urban heat islands

24 Apr 2024 | Science Notes

Another point made in Martin Durkin’s popular climate change movie is that measured warming has been exaggerated by urbanization over land. University of Guelph economist Ross McKitrick is quoted saying “Some places warm a lot and some places don’t warm much. and it turns out that it’s highly correlated with the spatial pattern of economic activity.” He showed this phenomenon in a set of studies published between 2004 and 2013, which eventually led the IPCC to concede that there was “significant evidence for such contamination of the record”. But of course they kept on using the data anyway. Durkin also interviews Dr. Willie Soon whose coauthored 2023 paper compared the official warming rates with warming measured using only rural records. Soon claimed that: “We combine all the best rural stations... [and if you] use only rural you get a very different kind of picture.... What we see is that basically we have a warming from 1900’s or so to the 1930s and 40s, and then it cooled in a substantial way to the ’70s, ’76 or so. Instead of a long-term systematic warming trend, it has a variability. Every 50 – 60 years or so. Kind of a variation.” Fact check: True.

From the Soon et al. paper we get this graph for the Northern Hemisphere land surface:

The panel on the left shows the official record, which relies on rural and urban stations, and shows a warming trend of +0.89 C per century. But the panel on the right shows the rural-only record for the same time span in which the warming is only +0.55 C per century, and the temperatures after 2000 are only a little higher than they were in the 1940s.

The IPCC claims that they remove all the effects of urbanization from their data. But if they did, the rural and urban records would look the same and they don’t.

A separate analysis of this issue was published by Italian physicist Nicola Scaffeta in the journal Climate Dynamics in 2023. Scaffeta noted that urbanization causes nighttime lows to rise, but doesn’t tend to lift daytime highs as much. So a warning flag of “warming” driven by urbanization not an actual widespread increase in temperature is if the gap between daily highs and lows gets significantly smaller.

The effect will also show up if warming is driven by greenhouse gases. But it won’t be as large because daytime highs will go up more. And by comparing model-generated data to temperature records around the world Scafetta showed that the gap in observed temperature records between daytime highs and lows shrunk by more than what climate models predicted, which is consistent with the warming being driven at least in part by urban heat island effects, which climate models ignore. By estimating the size of the effects and removing them from the data, Scaffeta also showed that the surface warming trend came roughly into line with the smaller warming trend in the satellite record than in the thermometer one.

So Durkin and his guests are on solid ground here. There is evidence that urban heat island effects contaminate the temperature record, and the IPCC ignores it because it’s an inconvenient truth.



5 comments on “ClimateMovie fact check: Urban heat islands”

  1. On the UHIE the painstaking work of Roy Spencer et al over several years (and now peer reviewed and ready to publish, I believe) should be studied by all interested in this topic. His work shows that at the present UHIE acounts for about 0.3C of the 1.1/1.2C rise indicated from land/sea based station (https://www.drroyspencer.com/2023/11/a-new-global-urban-heat-island-dataset-global-grids-of-the-urban-heat-island-effect-on-air-temperature-1800-2023/) .
    This is more or less the same as Willie Soon's charts above (difference of about .35C per century).

  2. I drive motorcycle for personal enjoyment. I know this makes me a bad person, burning fossil fuel without any reason.
    However, when you sit in the wind without climate control, you notice the constant change in temperature as you move along. To feel this through your safety gear, these changes must be substantial. How do they measure global temperature to within 100th of a degree is beyond me.
    But the biggest change occurs when one returns to the city. The increase in temperature is shocking, and it starts from the first street you cross.

  3. And this urban heat island effect is bound to increase substantially in North America,with out of control immigration in both countries.These people
    need new dwellings,for living and working,almost all will be in the cities.And our civic leaders want to intensify urban density to boot.While many of them live in suburbs nowhere near these congested cesspools.And keep demanding that everyone reduce their carbon footprint,except them!
    Once again,it's do as I say,not as I do...

  4. The movie was filled with disinformation and character attacks o all government fun ded science. It was a disgrace. More isappointing is how conservatives celebrated the movie, including this website. No fact checking, just cheerleading. My review of the movie:
    UHI effects are impossible to estimate beyond saying they add to warmer nights. So does greenhouse warming. This articles was wrong on that issue. Greenhouse warming is most effective at night.
    NASA-GISS claims moving land weather stations from urban environments to suburban airports reduced UHI, and future UHI increases.
    The claim that satellite data eliminate warming from UHI is false.
    UHI can affect any land weather station, even a rural station, if a town grows around what used to be green land.
    Most important is that 71% of our planet is oceans with NO UHI
    NOAA has two weather station networks: USCRN of 137 rural weather stations and nClimDiv with a variety of about 10,000 weather stations,
    The warming rate of USCRN since 2005 is +0.34 degrees C. per decade, while nClimDic is +0.27 degrees per decade. The rural USCRN weather station network reflects FASTER warming than the mainly urban and suburban nClimDiv. That contradicts the longstanding claim that rural areas warm slower. A movie or article that leaves out contradictory data is not being honest.

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