The urban heat island effect adds far more non-climatic heat to temperature station records than can be reliably controlled for.

An analysis of 10 cities from across the globe (Kara and Yavuz, 2025) reveals airports and industry centers are, on average, 2.5°C to 2.8°C warmer than neighboring green spaces.

“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.”

The urban heat island effect can leave airports and industrial centers as much as 12°C warmer than nearby vegetated, forested areas.

“Mexico City’s green spaces are up to 12.13 °C cooler than its urban core.”

Warming trends in recent decades are generally confined to urban areas, whereas non-urban areas have been cooling. For example, from 2001-2021 urban areas warmed +0.04°C/yr, but vegetated, bareland, and water body areas cooled -0.07°C, -0.03°C, -0.04°C/yr, respectively, in the city of Chongqing.

“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.”

Image Source: Kara and Yavuz, 2025