Figure 1. Comparison of Wauseon and Cleveland mean annual temperature traces. The two data sets track each other very closely, except that Wauseon has averaged around a degree or so less than Cleveland since the beginning of the records in 1870.
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.
Figure 1. Mean Monthly Temperature at Cleveland, 1856-2012. The warmest month is 2010 with a mean temperature of 56.0F; the coolest is 1857 with a mean of 37.8F. The linear trend is +0.24F per decade (+2.4F per century).
Below are graphs of the monthly mean temperature trace at Cleveland for the period 1856 to the present for the months of January, February, and March. The downtown station averaged around 1-1.5F warmer during these months than the present airport site during periods of record overlap. This would tend to make the displayed trend smaller, but this effect is probably mitigated to some degree by the increasing urban character of the airport site with time. All three months show a warming trend. The trend for January is fairly small, but March shows a significant warming trend of 3F per century over the entire record. This is consistent with trends found by NCDC for the State of Ohio. In all three graphs, the top ten warmest and top ten coldest readings are depicted.Figure 1. January monthly mean air temperature at Cleveland, 1856-2012. The warmest month is 1932 with a mean temperature of 40.2F; the coldest is 1977 with a mean of 11.0F. The average for the period of record is 27.1F; the current 30-year (1981-2010) normal is 28.1F.
Below is a graph showing the annual mean temperature in Cleveland from 1856 to the present. The data for 1856 to 1870 inclusive are from records taken by Gustavus Hyde, who resided near downtown Cleveland. The records from 1871 to 1940 inclusive are from official Weather Bureau readings taken at a rooftop exposure in downtown Cleveland. The readings from 1941 to the present are from Cleveland Hopkins International Airport (originally Municipal Airport). The data set has not been greatly affected by these discontinuities. There was a 35-year period (1871-1905) of overlap between Hyde’s records and those taken by the U.S. Signal Service Corps and Weather Bureau employees. The Hyde annual mean temperature averaged just 0.1F higher than the Weather Bureau annual mean temperature. The airport averaged about 0.5F cooler than the downtown rooftop station during a 13-year period of overlap from 1941 to 1954. This may seem surprising, given the fact that the airport is several miles from downtown and less influenced by Lake Erie being further inland. However, the difference was minimal on yearly average mean temperature. There were seasonal variations, though. The downtown site was a couple degrees warmer during the winter and fall, while the airport was somewhat warmer during the spring and summer months.
According to NOAA’s National Climatic Data Center, July 2012 was the third warmest on record in Ohio with a mean temperature of 77.6F. So, although very hot, the temperatures in July were not completely without precedence. The only months with a higher mean temperature are July 1901 and July 1934. The mean temperature was 77.7F in July 1901 and 78.1F in July 1934. Below are two images displaying the mean temperatures for July 1901 and July 2012. The map for July 1901 is taken from the monthly Ohio Climate & Crop Report for that month; the map for July 2012 is adapted from the dynamically-created High Plains Regional Climate Center maps. I added the color to the July 1901 map. The maps are not meant to provide an identical comparison between the months, as there may be differences in data quality and accuracy of the depictions shown.
Figure 1. Map of Ohio monthly mean temperature for July 1901, adapted from the July 1901 Ohio Climate & Crop Report.
Yesterday, I posted about observed water temperature increases at the Buffalo Water Treatment Plant site. To remove the seasonality from the data (and to better discern long-term trends), I converted all of the data since 1960 to an annual departure. The departure given for each year is relative to the average of a 1960-2012 base period. So far, 2012 has averaged 2.8C above the mean for the 1960-2012 period. The current warmest year on record is 1998 at 1.8C above the mean. The average annual water temperature has been increasing at 0.29C per decade since 1960.
Figure 1. Average annual water temperature departure at Buffalo, NY, 1960-2012. Note the steady trend towards warmer water temperatures.