How not to measure temperature, part 63

One of the strangest things I’ve learned in the past year about the US Historical Climatological Network is the propensity for placement of weather stations at sewage treatment plants.

The reason of course has to do with putting a thermometer at a facility that is staffed 7 days a week. That thermomter must be manually read once a day and the readings transcribed into a logbook. Waste Water Treatment Plants (WWTP’s) fit that requirement (as they have an operator on duty, often 24/7) but they themselves are their own mini islands of waste heat and humidity, especially in winter and overnight. Yet, a significant portion of the US climate data comes from these locations.

Some have grassy areas where a climate monitoring station could be placed, such as the one in Morrison, IL, and you’d think they would place it there, away from the sewage tanks. Unfortunately, no.

Click for a larger image, additional photos available here at surfacestations.org

My sincere thanks to volunteer surveyor Scott Finegan for these photos.

The Stevenson Screen housing the thermometer is about 5 feet away from each tank, while the concrete building in the background is some 50 feet away. You’d think that they could have placed the station a little further away. Again, as we’ve seen time and time again, the placement is not often about the best location, it is about convenience for the observer.

The GISS graph of temperature over the station history shows a fairly strong warming trend from about 1980 to the present. The question is, how much of that is from increased throughput of the sewage treatment plant responding to population growth, and how much of it is climate change?

Click for source graph from NASA GISS

According to NCDC’s Multi Metadata System database, this station has been at this location since at least 1948, even though a lat/lon accuracy update makes it appear to have been relocated in 1997, it has in fact been at this location all that time.

A nearby station, 25km away, Clinton, IA, is also in the GISS database and shows less of a trend during the same period:

Separating a climate change signal from the waste heat (and increasing effluent volume of the WWTP due to population growth) may not be a simple matter to disentangle. Since each WWTP has different conditions, coming up with a blanket correction would not be easy. Therefore, since the USA is highly oversampled spatially with weather stations that report daily data which can used for climate, it would be prudent in my opinion, to remove stations like this from the climatic database since the data produced by USHCN stations at WWTP’s may not be truly representative of climate.