By Steve Goddard and Anthony Watts
NCDC has done an first rate job raising Arizona summer temperatures, as seen in the graph below.
How did they accomplish this? – by magic! My favorite Arizona station is Ajo, near the Mexican border. Until 1984, temperatures were dropping – as seen in the USHCN (RAW) plot below.
Apparently someone at USHCN didn’t like that trend, so they made up homogenized an extra 25 years of data with a sharp upwards trend. This spreadsheet shows the USHCN data. Note that there aren’t any years after 1985 which have a full year’s data, and no years after 1985 with a full summer’s data.
For example, note this B91 form from the Ajo observer for July 1987, missing 10 out of 31 days of data:
Here is the adjusted monthly mean maximum data plotted from NCDC:
The image below shows Ajo adjusted maximum mean (black) on top of raw maximum mean (red.) Note that they are identical until 1970, when the magical adjustments kicked in. Click on it for a clearer image.
The station is not well sited. Note the MMTS temperature sensor is inside the white stucco patio wall enclosure at right:
Here’s another view:
Photos by surfacestations.org volunteer Bob Thompson
While the near A/C heat exchanger units are comical, wind sheltering and building proximity are also likely contributors. According to NCDC MMS metadatabase, in 2002 the station was switched from a Stevenson Screen to the MMTS sensor in the location shown above. Since NCDC does not make the site sketches that exist for all stations public, we can’t see the plan map showing where the Stevenson Screen was. However, the site survey from Bob Thompson tells us:
Site description and known history: The station was previously located on a nearby hilltop, but is now close behind a Phelps Dodge administration building adjacent to an open mine. I did not find any record of the relocation, but there is nothing any longer atop the hill.
There was a notation in the NCDC MMS Metadata remarks though, saying that the station had been moved 845 feet to the northeast.
The dates don’t match the date of the equipment change in 2002 though, and since the MMTS sensor requires a cable, it is likely that it was moved when the equipment change was noted in 2002.
Most likely the metadata citing the date of the move is wrong, and/or it took NCDC time to catch up with the change made by NWS personnel.
This Google Earth view, dated July 13th, 2006 shows the location of the temperature sensor at Ajo at the Phelps Dodge plant. Basically in the middle of an industrial zone:
In this more recent aerial photo from Bing Maps, it appears the facility has been closed down, and the buildings removed. They even abandoned 3 locomotives previously used to shuttle ore cars:
Note while the buildings are missing, the asphalt parking lot to the SE of the office is new.
Here’s a view with the GE ruler, showing where the Stevenson Screen likely was:
Here’s a closeup view of where the MMTS and rain gauges are:
Interactive view at Bing Maps is here
The point of all this is that this station has the following problems:
- Poor siting – building proximity
- Station move
- Sensor change from Mercury/Stevenson Screen to MMTS
- A nearby dynamic industrial environment with rapidly changing infrastructure and albedo as shown by aerial maps
- Missing/incomplete observer data over a long period, likely due to observer not recording data on weekends, holidays, vacation days, sick days.
- Incorrect/conflicting metadata at NCDC
- post facto adjustments to infill missing/incomplete observer data
That’s a lot of uncertainty added to the base measurement. Many stations have similar problems. The measurement environment is hardly static, yet we are looking for small variations in the climate in the midst of all this noise and uncertainty.
Other Arizona USHCN raw station data is below, showing about equal numbers of stations with declining and increasing maximum mean temperatures over the last 80 years. In Arizona, it’s all about the daytime heat, not the nighttime low.
Raising Arizona was probably Nicholas Cage’s best movie. In the end, they decided to be honest and give Nathan Arizona’s baby back. Can we expect the same?