Whither Your Weather Depends on Station Location

July 24th, 2009 by Leave a Comment

By Benita M. Dodd

For years, Atlanta’s Hartsfield-Jackson International and Chicago’s O’Hare airports have competed for the title of nation’s busiest airport. Last year, Atlanta won. As the official temperature stations for their respective cities, however, it seems the two airports tie – for the dubious honor of distorted data. And they’re not the only ones.

In 2008, meteorologist Anthony Watts wrote in the Illinois-based Heartland Institute’s Environment and Climate News: “The community around O’Hare was much smaller during World War II, when the airport was built, than it is now. The area had a significantly less-urban population and lacked the acres of concrete and asphalt that exist there today.”

You could replace “O’Hare” with “Hartsfield-Jackson,” and the same would be true.

Watts has completed a study, “Is the U.S. Surface Temperature Reliable?” that catalogs 865 of the 1221 U.S. Historical Climatology Network (USHCN) weather stations around the nation. He found that “89 percent of the stations – nearly 9 of every 10 – fail to meet the National Weather Service’s own siting requirements that stations must be 30 meters (about 100 feet) or more away from an artificial heating or radiating/reflecting heat source.”

In its FAQs online, the National Weather Service’s North Georgia field office at Peachtree City explains why Atlanta’s night-time temperatures are so much warmer than the rest of North Georgia: “The temperature is taken at Hartsfield-Jackson International Airport, which is affected by a phenomenon known as the “Urban Heat Island.” On relatively calm, clear nights temperatures in urban areas are affected by the concentration of concrete/asphalt, and also human activity. Concrete and asphalt tends to retain heat through the night, while more grassy or otherwise vegetated areas cool off. Activity related to humans, such as operating automobiles and aircraft, generates heat and also stirs the air, which interferes with the nighttime cooling process.”

It’s worse: Atlanta’s airport was born 85 years and 287 acres ago as Candler Field on the site of an abandoned auto racetrack. In 1929, the City paid $94,400 for the land and named the facility Atlanta Municipal Airport. Back in 1920, Atlanta was the nation’s 33rd largest urban area, home to a little over 200,000 people living within 26.2 square miles. The airport doubled in size during World War II. In 1942, with 1,700 takeoffs and landings in one day, the airport was declared the nation’s busiest in terms of flight operations. More than a million people came through the airport in 1948; by 1961, it was over capacity at 9.5 million per year.

Flash forward to 2008, when the airport saw more than 90 million passengers and more than 978,000 takeoffs and landings – a round-the-clock average of 111 operations an hour. Today, the airport covers 4,700 acres, or 7.3 square miles. That’s 28 percent of the size of 1920s’ Atlanta and 16 airports the size of Candler Field. Not only that; nearly 30,000 public parking spaces are at the airport and 30 shuttle services operate from the airport, along with about 55,000 employees.

What’s the significance of these soaring numbers?  This is the tip of the iceberg – or the heat island, so to speak. Since 1928, Atlanta’s official weather station has been located at the airport. Its location – impacted by the urbanization, traffic, runways and the removal of vegetation at the airport and surrounding areas – affects its readings, today and historically. And that is critical as government, scientists and activists seek to base policy on climate trend data generated by Atlanta’s and other such temperature stations.

The same holds true for readings from stations in urban areas such as Macon, Athens and Columbus, which are microclimates, impacted by infrastructure, and are risky markers for climate change trends. Surface thermometers that were once in rural or remote areas reflect higher temperatures as urbanization’s effects encroach.

A photograph of Atlanta’s airport weather station from the National Weather Service shows the runway lights next to the station. Watts’ study, which can be found at www.heartland.org/books/PDFs/SurfaceStations.pdf, shows two Georgia stations. One, in Gainesville, is between two driveways and one in Tifton is near a road, sidewalk and air-conditioning units. That wasn’t always the case, but changing conditions impact the consistency of data gathering, reduce the effect of comparisons and artificially bolster the case for global warming.

“The conclusion is inescapable: The U.S. temperature record is unreliable,” Watts’ study finds. “And since the U.S. record is thought to be ‘the best in the world,’ it follows that the global database is likely similarly compromised and unreliable.”


Benita M. Dodd is vice president of the Georgia Public Policy Foundation, an independent think tank that proposes practical, market-oriented approaches to public policy to improve the lives of Georgians. Nothing written here is to be construed as necessarily reflecting the views of the Georgia Public Policy Foundation or as an attempt to aid or hinder the passage of any bill before the U.S. Congress or the Georgia Legislature.

© Georgia Public Policy Foundation (July 24, 2009). Permission to reprint in whole or in part is hereby granted, provided the author and her affiliations are cited.

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