Arguments
It's microsite influences
The skeptic argument...
It's microsite influences
U.S. weather stations have been located next to exhaust fans of air conditioning units, surrounded by asphalt parking lots, on blistering-hot rooftops, and near sidewalks and buildings that absorb and radiate heat. 89 percent of the stations fail to meet the National Weather Service’s own siting requirements that stations must be 30 metres away from an artificial heating or radiating/reflecting heat source. (Watts 2009)
What the science says...
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| Microsite influences on temperature changes are minimal; good and bad sites show the same trend. | |||||
The website surfacestations.org enlisted an army of volunteers to photograph US surface temperature measurement stations and document stations located near parking lots, air conditioners, or anything else that might impose a warming bias. They found that 89% of the stations did not meet the US weather service siting criteria in one way or another. That is not good. Does this prove that a US warming trend is just the artificial influence of parking lots and air conditioners on the temperature record coming from "bad" stations?
No. Actually, an analysis shows that "good" and "bad" stations show very similar trends for temperature over time. The chart below compares data from stations that surfacestations.org identified as "good", as well as "bad" stations. Notice that "good" stations track very closely to "bad" stations, and actually the "good" stations show more of a warming trend!
Figure 1. Annual average maximum and minimum unadjusted temperature change calculated using (c) maximum and (d) minimum temperatures from good and poor exposure sites (Menne 2010).
The volunteers from surfacestations.org deserve credit for pointing out siting problems of the US Weather Service temperature measurement stations. Unfortunately the fact that "good" and "bad" stations show the same upward trend proves that warming in the US is not just a measurement problem. Temperatures are trending upward around the globe, not just in the US. Microsite influences on temperature measurements in the US can't explain the US temperature rise, much less the global rise.
Last updated on 31 August 2010 by Jim Meador.
In cold weather the opposite can occur...the 'bad' stations will respond more slowly to increasing T due to the thermal inertia of those same buildings. In other words, the T swing max-min could be greater in the 'bad' stations but dis-appears in the averaging process.
So maybe there is an element of self-compensation here which could be determined by looking at more detailed data.
2) Why do your graphs only go back to 1980 while other stations have data going back more than 100 years on the graphs of surfacestations.org?
Re. #2, a good question. I looked up the Menne article and the Watts 2009 article to which it is a response. Watts suggests two driving causes for the upward bias of temperatures: The change in paint spec in 1979 and the introduction of the new type of thermometers in the 1980s. I suspect that Menne, et al, restricted their period of reporting to that which Watts was concerned about.
I can't predict what difference that made, but for someone really concerned about siting of instruments, he introduces his own siting problems.
The problem is that it isn't. National has fresh dark gravel spread around their thermometer site (new google satellite compared to old) and they are consistently high by 2-3 degrees on radiational cooling mornings. The anomaly doesn't show up as much on windy or cloudy mornings. National's lows are also 5 to 10 degrees higher than neighboring weatherbug sites (mostly at schools) but that is a river and heat island influence that hasn't changed much over the years.
If the washpost link above doesn't work (their site is sometimes unruly), the NWS discussion was also quoted here; http://www.americanwx.com/bb/index.php/topic/23896-record-summer-watch-where-will-we-finish/