Chicago Temperature Station Riddled with Problems

Published February 1, 2008

An analysis of the official temperature station at Chicago’s O’Hare International Airport illustrates many of the problems that lead to false indications of global warming.

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.

It’s a safe bet, then, that there is an urban heat island effect at O’Hare that would make temperature readings indicate a gradual warming that has nothing to do with global or regional climate.

Database Riddled with Errors

O’Hare also suffers from inconsistency in reading locations.

According to the National Oceanic and Atmospheric Administration (NOAA) database, O’Hare’s Automated Surface Observation Station (ASOS) is currently located at the Air National Guard Base there.

But that database must be wrong because, according to the Illinois National Guard, they moved from O’Hare in 1993.

This isn’t surprising. The NOAA/National Climatic Data Center (NCDC) database is riddled with such errors. The current registered latitude and longitude–41.9786N, 87.9048W–places the station in the middle of the parking garage, which is definitely not accurate.

Curiously, the NOAA/NCDC meteorology measurement system database reports that even though this station is listed as an “ASOS,” it doesn’t have the typical ASOS equipment found at other airports. It appears one of the busiest airports in the world has nonstandard equipment, with one exception. The database lists “Hygrothermometer,” though it doesn’t identify the model. Model HO83 is known to be fraught with errors.

Changing Locations, Equipment

The NOAA database says prior to 1992 the temperature station was at the O’Hare Corporate Tower on West Higgins Road, and prior to that at the Hardstand Operations Building (as recently as 1989), and before that at the old air terminal (circa 1958 and earlier).

In 1958 the station used a standard Stevenson Screen and mercury max-min thermometers. Today it is a completely different set of equipment in a completely different location in completely different surroundings.

Perhaps most important in determining whether the station’s readings are comparable over time, the temperature station is now in proximity to a much larger and busier airport.

All of these factors negatively affect scientists’ ability to accurately measure long-term temperature trends. The O’Hare station is a vivid example of the problem.

Anthony Watts ([email protected]) is a veteran meteorologist from Chico, California. Watts is currently assembling data and conducting a comprehensive analysis of the nation’s official temperature reading stations, which can be found at