Climate scientists account for urban heat island effects, corroborate data | Fact check

Kate S. Petersen, USA TODAY
Updated ·5 min read

The claim: Post implies higher temperatures are only the result of urban development, not global warming

An April 13 Facebook post (direct link, archive link) shows two images of urban areas. One, dated 2005, shows a tree-lined street with a grass median. The other, dated 2023, shows what appears to be the same street with a concrete median and no trees.

"When your (sic) wondering why it wasn't so hot before," reads the caption.

The post was shared more than 2,000 times in a month.

Some social media users took the post as evidence that global warming isn’t happening.

“ABSOLUTE CRAP, ice melting, sea levels rising, all created by simple minded individuals with no environmental understanding, no lessons in history and not much COMMON SENSE,” one user commented.

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Our rating: Missing context

The implied claim is false. The Earth is warming due to an increased concentration of atmospheric greenhouse gases as a result of human activity. Temperature data from sensors impacted by urban heat is corrected and corroborated by sensors that are unaffected by urban heat.

Temperature readings from urban areas are reliable

Urban infrastructure, such as concrete roads, buildings and parking lots, absorb more of the sun's energy than trees and grass, which causes urban landscapes to be hotter than less developed areas. This results in "urban heat islands" − areas where the average temperature is hotter than surrounding areas.

The Facebook user who posted the image, Climate Change is Crap, told USA TODAY that increased heat due to urban development "changes the readings on thermometers and gives us a false reading."

However, it is a myth that urban heat islands explain the steady rise in the Earth's global temperatures, Marshall Shepherd, director of the University of Georgia's atmospheric sciences program, wrote in Forbes. He referred to the idea as a "zombie theory" − a narrative reiterated even after substantive scientific evidence has shown it to be false. He noted some of the fastest warming is happening away from urban areas, like in the Arctic.

While temperature stations located in urban areas can be influenced by their surroundings, scientists make adjustments to the data to account for this issue, National Oceanic and Atmospheric Administration spokesperson John Bateman previously told USA TODAY. And researchers have various strategies they use to ensure these corrections are accurate.

For instance, data trends are very similar between the corrected readings from more than 10,000 U.S. temperature stations used by NOAA (which include those in urban areas) and uncorrected data from the Climate Reference Network − a collection of more than 100 stations positioned in pristine settings, he said.

Fact check: Climate data reliable and collected from many sources, not ruined by airports

"While urban heat islands and other urban-correlated biases are real − and can have a big effect − current methods of detecting and correcting ... are generally effective in removing that bias," Zeke Hausfather, a climate scientist who has studied the impacts of urban heat on U.S. temperature readings, wrote in Real Climate. "Claims that urban heat islands explain any substantial fraction of the recent warming in the U.S. are just not supported by the data."

Multiple lines of evidence show Earth is warming

Even if temperature sensors near urban areas were untrustworthy, researchers have also documented global warming using tools that are not located on land. For instance, satellite-based sensors have detected atmospheric warming, and sensors on ships, satellites and robotic instruments have documented ocean warming.

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In addition to detecting global warming itself, scientists have documented the results of global warming caused by greenhouse gas emissions from human activity. These include:

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This article originally appeared on USA TODAY: Climate scientists account for urban heat island effects | Fact check