Climate Experiment

Many people will be traveling over the coming Christmas and New Years holidays. Most probably have all the equipment required to conduct a rudimentary climate experiment – a vehicle with a digital thermometer which measures outside air temperature. Don’t be concerned about the accuracy of this digital thermometer, since: it was probably calibrated more recently than most of the thermometers which contribute temperature data to the Global Historical Climate Network (GHCN); and, you will be measuring temperature anomalies rather than actual temperatures, so absolute accuracy is not essential.

The vehicle, particularly if stored in a garage, must be driven for several minutes to allow the digital thermometer to come to equilibrium. Then the experiment can begin. Observe the temperature as you travel and note your surroundings. This can be a wonderful learning experience for children, as well as a way to keep them busy and avoid: “Are we there yet?”

The most interesting experiment, from a climate science perspective, is the demonstration of the Urban Heat Island (UHI) effect. This experiment is best done either in the middle of the day or in the middle of the night, when ambient temperatures are not changing rapidly due to the morning warmup or the late afternoon or evening cool down period.

Driving through a city, from the exurbs through the suburbs and the city and then out through the suburbs and finally through the exurbs on the other side of the city completes this experiment. Observed temperatures will change significantly, warming as you drive toward the city center and cooling as you return to the exurbs. Depending on weather conditions, a change of 5-10^oF is typical. The change may be even greater in very densely populated urban areas. This experiment also clearly demonstrates the potential for human activity to influence climate in limited areas.

Passing over, or even near, a large body of water can cause a change of 2-3^oF, depending on the season. In summer, the temperature will decrease as you cross or pass the water. In winter, the temperature will increase, unless the surface of the water is covered with ice.  

Climbing or descending through several thousand feet of altitude can also cause multiple degree changes in measured temperature.

These simple experiments, conducted in conjunction with holiday travel, demonstrate the significance of the location of temperature measuring stations, since these changes are at least as large as the global warming reported over the past ~150 years; and, frequently, several times greater than this reported warming.