Warm Bias, Invented

Part II of the Daughter of Climategate series.

Part of U.S. contribution to the NASA temperature index comes from the “U.S. Historical Climate Network” (USHCN) which was designed to detect ‘global warming.’ Well, it does — but in a very unscientific manner.

For nearly 150 years, temperatures worldwide were measured by human beings that read thermometers in wooden whitewashed Stevenson Screens:

As documented by Anthony Watts’ excellent Surface Stations Project, we have seen that the conversion to electronic thermometers in the early to mid-90′s has introduced a warm bias to the temperature data. Why? The electronic thermometers have a maximum 50′ cable run. And, where is electricity available on the outside of a house or other structure?  At the air conditioner. And, what does an air conditioner vent?  Hot air.

Here is a perfect example of the problem in Georgia. You can see the old Stephenson Screen in the background. The new electronic instrumentation is next to the building (a no-no by itself that introduces a warm bias) right next to the air conditioner and its warm air exhaust.

This is one of my favorites, from Kentucky. The temperature sensor (the white round object) is over concrete (another no-no), up against the house (a no-no), above the air conditioner and its hot air and over the family bar-b-que.

While the full extent is not known, there is little question that the change in instrumentation has introduced a warm bias into the temperature data since early to mid-90s.


These new instruments have been installed in many nations, so it is a worldwide problem.

But, there is more to the story as we’ll see in the next installment.

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