The Rules

To qualify as a properly maintained temperature station, accurate temperature sensors must be placed in an elevated, slatted box on relatively flat ground surrounded by a clear surface on a slope below 19 degrees. Surrounding grass and low vegetation ground cover must be less than 10 centimeters high. Temperature sensors must be located at least 100 meters from artificial heating or reflecting surfaces, such as buildings, concrete surfaces, and parking lots.
The sensors must also be far from large bodies of water, unless it is representative of the area, and even then located at least 100 meters away. No shading of the temperature sensors should occur when the sun elevation is greater than 3 degrees.
Meeting the above specifications is important to ensure no artificial heating or cooling signal is reported in the data. For example, if a parking lot is built adjacent to a temperature sensor, the asphalt and running engines of automobiles will provide an artificial heat source that would skew the temperature data to report a warming that does not in fact exist.

Temperature Station Quality

In 1997, a study by the U.S. National Research Council concluded the consistency and quality of temperature stations in the United States was “inadequate and deteriorating” and the U.S. Historical Climatological Network (USHCN), the organization charged with maintaining the temperature stations, was doing little to address temperature station inadequacies.

As of 2010, the USHCN maintains all of the 1,221 official weather stations.  Using a scale from 1 to 5, stations that are properly maintained receive a rating of 1 and stations that are severely compromised by artificial temperature signatures (being located adjacent to an artificial heating source, such as a building, rooftop, parking lot, or concrete surface, for example) receive a 5. Of these stations, far more stations fail to meet the standards than do. In fact, approximately 70 percent of the 1,221 official temperature stations receive a 4 or 5 rating, and only 4 percent receive a rating of 1. That’s right, only 4%!

Let’s look at an example, and the station at Monterey, CA is a perfect example!


Temperature sensor rules one by one:

a) The sensor should be mounted 5  feet +/- 1 foot above the ground.  Violation!

b) The ground over which the shelter is located should be typical of the surrounding area. Violation!

c) A level, open clearing is desirable so the thermometers are freely ventilated by air flow. Do not install the sensor on a steep slope or in a sheltered hollow unless it is typical of the area or unless data from that type of site are desired. Pass!

d) When possible, the shelter should be no closer than four times the height of any obstruction (tree, fence, building, etc.). Violation!

e) The sensor should be at least 100 feet from any paved or concrete surface. Violation!

Remember, the temperature recording station above is not an anomaly, it is the norm (approximately 70% are rated 4 to 5 out of 5)!

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