Critics of the temperature record often focus on non-climatic impacts of land use and urbanization, and the effect these could have in producing a spurious warming trend. To examine these impacts, I’ve been looking at rural sites with reliable, long periods of record. One of the longest reliable climate records in Ohio has been maintained in the small town of Wauseon (population 7,332), in the far northwest corner of the state. In January 1870, Thomas Mikesell began taking weather observations at his home. In addition, to the weather observations, Mr. Mikesell also took meticulous records of the fauna and flora in his hometown. These phenological records are currently the subject of a research project to gauge the impacts climate change is having on the natural world. Based on records compiled during the early years of the Ohio Monthly Weather Review and my own personal observations today, I would estimate that spring is arriving from 2 to 3 weeks earlier than it did 120 years ago in terms of bloom and leaf-out dates. The study mentioned above should help shed better light on this.

Figure 1. The Wauseon station at the Mikesell residence, circa 1908.

After Mr. Mikesell’s death, the temperature station was moved to the Wauseon Wastewater Treatment Plant. As shown by these images from surfacestations.org, the Wauseon station is a high-quality, well-sited station in a rural, small town environment.

Wauseon_338822_South_22Figure 2. View to the south of the Wauseon MMTS unit.

WAUSEON WATER PLANT, OH, MeasurementFigure 3. Overhead view of the Wauseon MMTS, showing the distance to the nearest structure at 12.0 meters (or 39.3 feet).

Attached below is a graph showing the mean annual air temperature recorded at Wauseon for the period 1870-2011. The warmest year occurred in 1931 with a mean temperature of 53.3F. The coldest year on record was 1875, with a mean temperature of 44.2F. The linear trend is +0.11F per decade (+1.1F per century). These values are based on the actual raw data, and may vary from the figures displayed by NCDC. In particular, the switch from the Cotton Region Shelter to MMTS is known to have introduced a slight cooling bias. Prior to deployment of MMTS, observers usually set the maximum thermometer during the late afternoon or early evening. This resulted in spurious high temperatures on some days, since the temperature the following day did not always meet or exceed the set maximum and the set maximum would be recorded as the high temperature. The MMTS is also known to run slightly cooler than the sheltered LiG thermometers. NCDC corrects for inhomogeneities in the data set.

Figure 4. Mean annual temperature at Wauseon, OH, 1870-2011. The top ten warmest and coldest years are indicated on the graph.

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