Study sponsored by NOAA finds that poorly-sited air temperature monitoring stations have artificially boosted global warming data

Anthony Watts of Watts Up With That reports on an important scientific paper sponsored by the National Oceanic and Atmospheric Administration (the official keepers of temperature records) that confirms what Watts and other critics have maintained for years. To its credit, NOAA decided in 2012 to test Watts’s critique that a substantial portion of the surface air temperature monitoring stations that are used to generate data for claims of global warming are located in places that have become surrounded by urbanization in the form of asphalt and concrete surfaces and other facilities that absorb heat during the day and discharge it at night -- thereby artificially raising the average air temperatures.

Here is one example Watts provides of a ridiculously-sited air temperature monitoring station:

USHCN weather station in a parking lot. University of Arizona, Tucson

As a scientist, Watts uses the scientific and technical terminology but explains it. For example:

I have published on the topic in the scientific literature, and found this to be true based on the science we’ve done of examining the USHCN and applying the siting methodology of Leroy 2010.

In Fall et al, 2011 we discovered that there was a change to the diurnal temperature range (DTR). It decreased where stations had been encroached upon, because of the heat sink effect of man-made materials (asphalt, concrete, bricks, etc.) that were near stations.

For layman readers that don’t know what diurnal variation is, it is the daily variation of temperature due to the variation of incoming solar radiation from rotation of the earth on its axis.

Lo and behold, the scientific paper promised in 2012 has been published and it confirms the critique. The language is technical, but the results make common sense and confirm that claims of global warming have been inflated:

Like I’ve said all along (and been excoriated for saying so) they found exactly what we did.

Impacts of Small-Scale Urban Encroachment on Air Temperature Observations

Ronald D. Leeper, John Kochendorfer, Timothy Henderson, and Michael A. Palecki

Abstract (bold mine)

A field experiment was performed in Oak Ridge, TN, with four instrumented towers placed over grass at increasing distances (4, 30, 50, 124, and 300 m) from a built-up area. Stations were aligned in such a way to simulate the impact of small-scale encroachment on temperature observations. As expected, temperature observations were warmest for the site closest to the built environment with an average temperature difference of 0.31 and 0.24 °C for aspirated and unaspirated sensors respectively. Mean aspirated temperature differences were greater during the evening (0.47 °C) than day (0.16 °C). This was particularly true for evenings following greater daytime solar insolation (20+ MJDay−1) with surface winds from the direction of the built environment where mean differences exceeded 0.80 °C. The impact of the built environment on air temperature diminished with distance with a warm bias only detectable out to tower-B’ located 50 meters away.

The experimental findings were comparable to a known case of urban encroachment at a U. S. Climate Reference Network station in Kingston, RI. The experimental and operational results both lead to reductions in the diurnal temperature range of ~0.39 °C for fan aspirated sensors. Interestingly, the unaspirated sensor had a larger reduction in DTR of 0.48 °C. These results suggest that small-scale urban encroachment within 50 meters of a station can have important impacts on daily temperature extrema (maximum and minimum) with the magnitude of these differences dependent upon prevailing environmental conditions and sensing technology.

Hat tip: Roger Luchs