Hot Town

Monday, April 22, 2024

Hot Town

It wasn’t until two NASA scientists developed the technology and technique for measuring the earth’s surface temperature via satellite in the late 1970s that we had any real idea of temperatures all around the world, and thus of the whole earth. Those scientists were Roy Spencer and John Christy, and it has only been since then that we have had a reliable global surface temperature record. Everything prior to that was essentially guesswork for most of the planet.

Temperature measurements were only available for specific geographic locations, and those were limited largely to inhabited places in North America, Western Europe, and a handful of other locations close to human population centers. A single thermometer in a remote location such as central Africa, for instance, was used to extrapolate the daily temperature conditions in all directions for hundreds of miles where data simply didn’t exist.

Thermometers were not invented prior to the 17th century, and standardized means for producing, calibrating, siting, and recording their measurements consistently date back no farther than the early 19th century. Yet one of the earliest understandings gleaned from measuring temperature was that cities are warmer places than forests or farmland. As this finding was confirmed repeatedly throughout the 20th century, the pattern and mechanisms were better understood.

Places built up for human habitation have sealed up natural surfaces and covered them with cement and stone, as well as materials that absorb solar energy and release it slowly into the night. Human homes and businesses produce and release waste heat into the environs year round, both during the heating season and during the cooling season, where the indoor warmth is dumped into the outdoors. Modern materials like road pavement and roof tar catch and radiate solar heat on summer days. The combined processes result in higher temperatures at the low end of the daily cycle than is found in the woods and fields.

According to research from Christy and Spencer, the resulting urban heat island (UHI) effect is likely much stronger than previously believed. They estimate the UHI accounts for some 22 percent of the global warming trend in the Lower 48 temperature record between 1895 and 2023. It also means that global warming is most likely overstated by a lot, since much of the global temperature data is extrapolated from North America.

The weaknesses of any claims regarding global temperature patterns based on such an almost universal lack of reliable, comparable data should be obvious. But fear is more compelling than fact to our collective psyche. Thus, we worry that we’re warming the planet, even though there is still ice at the poles and in glaciers, which means there is still an ice age. Unlike previous ice ages, this one has never ended completely. Previous ice ages saw global ice disappear, to the best of our understanding based (as it must be) on proxy reconstruction data.

At any rate, rather than greeting the scanty available data with fear and induced panic, it would be nice if we could acknowledge that there’s a whole lot about our planet that we only poorly and incompletely understand. What is clear is that global warming appears to have occurred mainly in places where people have decided to inhabit in large numbers while recording temperatures. These are the urban areas to which people still flock as an ongoing, unbroken global trend.

Finally, I would add that Dr. Spencer’s website has lots of deep discussion on the science of planetary temperature measurement generally, and his recent pages on UHI over time contain some interesting illustrations of places today compared to the past. That is to say: there are colorful maps, pretty maps to look at. There’s no need to get all hot and bothered.