NASA Study Confirms Climatic Impact of Weather Station Relocation

UPDATE NOV 25: Anthony Watts did cover the mentioned LA weather station in a March 24, 2008 post. I was looking for the Earth Observatory link, while he mentions the JPL one. Still, my blog below adds to the story, by providing links to the original Poster Presentation and pointing out that many stations were moved around 1998-1999.

Perhaps there is a good reason why the study below is not mentioned in Watts Up With That or at surfacestations.org. Perhaps it’s just me unable to use Google properly. Or for some reason I am the first one making the connection.

So in full glare of all my ignorance I point to this Poster Presentation at the 16th Applied Climatology Conference, American Meteorological Society, Jan. 14-18, 2007, San Antonio, TX (joint with the 14th Symposium on Meteorological Observations and Instrumentation):

Patzert, W.C., S. LaDochy, J. K. Willis, and T. Mardirosian, 2007: Will the real Los Angeles stand up: Impacts of a station move on climate records (and record weather) (short Abstract) (long Abstract)

Some may remember seeing that study mentioned on NASA’s Earth Observatory (EO)’s “A Tale of Two Sites: Impacts of Relocating L.A.’s Weather Station” (Jan 17, 2007).

Since it’s a Poster Presentation, a brief note about the authors is due, to check their trustworthiness (you wouldn’t believe what is presented nowadays as “poster” in many scientific conferences):

“Mardirosian Mystery” aside: what is that they’ve found?

In August, 1999, the National Weather Service (NWS) moved the official downtown Civic Center weather station to the University of Southern California (USC) campus, a 3.78 miles (almost 6 km) distance to the southwest of its previous location near city center at the Department of Water & Power (DWP) […]

By moving the official LA downtown weather station location, weather is now recorded as cooler, drier and less extreme than at its original DWP location […] there appears to be a discontinuity in the records. Maximum and mean temperatures are cooler, especially Tmax. Minimum temperatures are similar for the two sites. DWP also records higher rainfall amounts, although there is great variability monthly and inter-annually. Extremes occur less often at USC than DWP. […]

Moving a weather station away from the city resulted in cooler, drier, and less extreme weather. And in a “discontinuity in the records”. That appears to vindicate all the work done by Anthony Watts and surfacestations indeed.

Consequences? For example:

[…] In the 2004-5 water year (July 1-June 30), the USC rain total was 37.25” (946.2 mm), second only to 1883-84, which had 38.18” (969.8 mm). However, DWP recorded 38.32 (973.3 mm), which would have been the wettest year on record for downtown Los Angeles had not the station moved […]

[…] At USC, the all-time record for highest temperature minimum for the date June 4th was set with 68oF (previous record being 66F in 1997). At DWP, the Tmin was 70F. […]

We are talking 973.3-946.2=27.1mm and 70F-66F=around 1C overestimated in downtown LA compared to the new site. In the first case, we would have heard about “yet another climate record” having been broken. In the second case, we would have been told a temperature value that is more wrong than the total estimated temperature increase from 1850 to today.

And it’s just one station, where they were “fortunate in that the original location (DWP) is still in operation and can be compared to the new site“. Sounds ominous doesn’t it? It means that most of the time, a new station’s measures are simply attached to the previous one’s, with no time provided for suitable medium-term comparison.

Actually, it’s worse. From the EO:

The National Weather Service moved the station [in 1999] as part of a nationwide effort to locate all official weather stations on ground-level sites in natural settings

In other words, there are many weather station records that are for all intents and purposes useless for comparing recent data to measure done before around 1999.

=========

And before somebody says that the above would have resulted in a spurious cooling trend for LA: it doesn’t matter. What matters is always the quality of the data.

And if NASA says that many weather stations have poor quality records, doubts on the very existence of an ongoing, potentially worrying global warming can only increase.

Has anybody noticed how the “warming trend” has almost stopped…exactly since 1999?