24 Hours of Climate Reality: Gore-a-thon – Hour 22

A new post containing a cartoon from Josh will appear every hour. At the end of the 24 hours, everything will be collated on a single page. Readers are encouraged to post skeptical arguments below, as well as offer comments on what has been seen from the Climate Reality Project so far.

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Warming up the thermometers

The surfacestations project found that the majority of official climate thermometers in the USA were improperly sited by the government’s own standards.

Many are near air conditioners or in parking lots.

Above: official USHCN weather station, in the parking lot, Atmospheric Science Dept. University of Arizona, Tucson. Photo: Warren Meyer

Many, like the University of Tucson shown above, have been closed by NOAA since the project started: An old friend put out to pasture: Marysville is no longer a USHCN climate station of record.

The first peer reviewed paper didn’t find a strong effect on the mean temperature, but we did find something nobody else had, and that is that the dirunal variation over the last century is flat.

Summary below:

Temperature trend estimates do indeed vary according to site classification. Assuming trends from the better-sited stations (CRN 1 and CRN 2) are most accurate:

• Minimum temperature warming trends are overestimated at poorer sites
• Maximum temperature warming trends are underestimated at poorer sites
• Mean temperature trends are similar at poorer sites due to the contrasting biases of maximum and minimum trends
• The trend of the “diurnal temperature range” (the difference between maximum and minimum temperatures) is most strongly dependent on siting quality. For 1979-2008 for example, the magnitude of the linear trend in diurnal temperature range is over twice as large for CRN 1&2 (0.13ºC/decade) as for any of the other CRN classes. For the period 1895-2009, the adjusted CRN 1&2 diurnal temperature range trend is almost exactly zero, while the adjusted CRN 5 diurnal temperature range trend is about -0.5°C/century.
• Vose and Menne[2004, their Fig. 9] found that a 25-station national network of COOP stations, even if unadjusted and unstratified by siting quality, is sufficient to estimate 30-yr temperature trends to an accuracy of +/- 0.012°C/yr compared to the full COOP network. The statistically significant trend differences found here in the central and eastern United States for CRN 5 stations compared to CRN 1&2 stations, however, are as large (-0.013°C/yr for maximum temperatures, +0.011°C/yr for minimum temperatures) or larger (-0.023°C/yr for diurnal temperature range) than the uncertainty presented by Menne at al (2010).

More detailed results are found in the paper, including analyses for different periods, comparisons of raw and adjusted trends, and comparisons with an independent temperature data set. More here

A follow up paper is in the works looking at other issues in the metadata, such as airports, rural/urban etc.

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