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| Source: NCDC |
“Last month I sent a 'spot check' of June’s measured temperature anomaly at the Coal Creek Canyon, Colorado, co-op station compared to NCDC’s analyzed temperature departure map for the month. Interpolating the NCDC map to my location gave an analyzed departure of +4F, compared to the actual station departure of only +1.0F.
On the map, Coal Creek Canyon is above the 2F contour, with an analyzed departure of about 2.5 or 3 degrees F. And the actual observed departure? +0.3 degrees F. Once again, NCDC adds 2 or 3 degrees to the observed temperature anomaly.
Could it just be this one station? No, since another mountain site with a long record about 15 miles to my north (Jamestown) had a monthly departure of -0.5F (yes, Minus). And the Denver airport site had +1.0F.
The NOAA headlines announce this as the 2nd warmest July on record nationally, but at Coal Creek July came in 12th place, out of 28 years of record. July 2003 was 6 degrees warmer than this past July, and July 1992 (the year after Pinatubo) was 4 degrees cooler.
I’ll keep checking this in future months, but I suspect the story will remain the same, with mystery adjustments inflating the temperature departures in one direction only.”
--TS
Hum. I'm a bit confused, and maybe I'm just reading this wrong. Why would Dr. Keen pair a "spot check" of June temperature anomalies with a map of July temperature anomalies? Anyway...
ReplyDeleteOne should keep in mind that Coal Creek Canyon is in a topographically complex area, which makes all interpolation methods difficult. (Temperature and precip in mountainous areas change dramatically over short horizontal distances due to sharp changes in relief). Think back to those fun days in GIS class! Also, an interpolated map will NEVER match every point measurement that was used to create the interpolation. Interpolation smooths out the details - that's the point! Sometimes a point will be above and sometimes the point will be below.
I'm not saying Dr. Keen doesn't have anything to be concerned about. We have many quality control issues to deal with here in the U.S. and around the world. It's important to question everything, we would be bad scientists if we just believed everything other people told us....it would just be helpful if people like Dr. Keen would provide additional context for the casual reader.
M.W.--
ReplyDeleteI read icecap.us on a pretty regular basis, and know that Dr. Keen is a frequent contributor to the site. He's also a good writer as I've read "Michigan Weather", "Skywatch West", and have glanced at other books he's written.
However in this case, I'll admit he's a bit hard to understand. I think it's because this was just a quick post he made, tailored to frequent visitors to the website and to his busy schedule as a professor.
In the first paragraph, he's talking about doing a spot check in June of his station at Coal Creek Canyon. (You'll notice he refers to it as "my location," implying that these are his actual measurements.) Then he opens the second paragraph by saying, "On the map..." He's obviously referring to the July NCDC map at this point, and one can infer that he's also talking about July temperature data at Coal Creek Canyon since the observed data he's talking about in this paragraph is different than the June data he mentions in paragraph one. So at this point, he's transitioned from June to July.
He concludes that the comparison between his measurements and the analysis performed by NCDC are 2 to 3 degrees different for the second straight month. To be sure that this isn't an isolated incident, he goes on to include July data from Jamestown and Denver, Colorado. Both of these locations also have lower departures from normal than the NCDC map indicates (and in the case of Jamestown, the actual temperature was actually slightly *below* normal in July 2010). So he actually does get a sampling of towns at different elevations. Denver's airport is a bit over a mile high, while Coal Creek Canyon and Jamestown are somewhere closer to 8,000'.
--TS