What I’d like to remark is that using local resident population (e.g. residents of Mannhattan) as a marker of the intensity of urbanization in the area) may be misleading. Heat generation in Mannhattan is partially created by non-residents that drive cars or sit in offices within the area (but live in the metro area or beyond). Thus the UHI effect should be measured in a different fashion. One proposal is using some station covering a similar historical period, located at the same general climate, but in a more rural area. In 1900 probably temps in Mannhattan were not much different than temps in areas in N.Jersey or Conn. that are now leafy suburbs, but the two may have unaccountably diverged over time between, say, 1900 and 2010. The difference may be a measure of the UHI.

Example from the city I live in now. The main station of Buenos Aires city is also in a kind of midtown park (the Agricultural School of BA University), surrounded by asphalt, cement, many-storied bldgs and many factorties. Nowadays this station routinely gives 3°C more than some stations located in the outskirts of the metro area (including the main airport), although all are within 30-40 miles of each other and within the same general climatic and geographical zone. I am now trying to reconstruct the series of the outskirts from records at various locations that start at different years and have some discontinuities, but my guess is I’ll find a divergence between the Agric School station and the more “rural” ones around this huge metro area (pop > 13 million). Has anybody done the same for NYC?

Is there anyone at NOAA that we can ask about the logic and justification for these specific corrections?

Has anyone at NOAA said whether or not they consider these corrections to be proper?

The main thrust of the post was to show the outrageous magnitude of the NCDC adjustments for NYC Central Park especially during the past 50 years. The difference between the raw and adjusted temperatures peaked out prior to 1990 at about 3.5°C! Justification, or the lack thereof for these adjustments are well discussed in about the first 100 posts, after which the responders strayed away from the basic atrocity of “UHI” adjustments of this magnitude and went to arguing about the change in siting, instrumentation and especially exposure…whether shaded or otherwise. Most of these effects are significantly less important than the magnitude of the adjustment itself. The effect of daytime shading from the sun is considerably offset by the limitation the same shading puts on the effectiveness of nocturnal radiational cooling.

Also, one should note that through this period, the CP raw data tracked very well with other NYC sites…LGA, JFK, EWR, TEB and the City Office in Lower Manhattan. These relationships were solid enough so that when the CP site became unmanned and observations were remoted to the new Rockefeller Center location of the NYC WX Office, we could spot a temperature sensor drift within a day or two. At this point we would call the Rock Center office and within a another day or two they would send someone out to the CP site to recalibrate the sensor system. We could tell exactly when this occurred because, depending on the degree of drift, there would be an observable discontinuity in the hourly METAR string. The problem was sharply reduced after the newer MMTS sensors were installed.

The point is that there can be no logical meteorological reason for altering the record by reducing NYC temps in the city by 6°F to 7°F in the 1960-1990 period, and then nearly linearly reducing the negative adjustment from 1990 to 2005 at about 1.7°C per year! That’s about the equivalent of moving the NYC thermometer southward to Richmond, VA.

I, and a few others, brought this obvious maladjustment to light some 2.5 years ago and have yet to receive an acknowledgment, much less a satisfactory answer.

Recently, NCDC quietly scrapped USHCNv1 UHI scheme and replaced it with a new measurement of “homogeneity” which uses individual station data inflection points (AKA change-point analysis) that are viewed as biases needing adjustment, and then combining the HCN stations with one of perhaps several nearby COOP stations to create a “pairwise” SHAP (Station History Adjustment Program) algorithm. A discussion of this program can be found in the 2009 July BAMS 90, 993-1007. Unfortunately, the SHAP algorithm and coding is not provided there or in the listed referenced papers.

Ironic that the place observation bias kicks in is in the exact correction they must fine painful to apply.

I can’t believe you missed the whole point that we’re not trying to take measurements in order to predict the weather. We’re trying to measure the
thermodynamic state of the earth for the purposes of CLIMATE studies.
The bottom line is that we operate on completely different levels of abstraction. Let’s just agree to disagree.

How about we agree that you don’t have a clue and you stop embarrassing yourself?