Chester County PA - Analytical Battle of Actual vs. Altered Climate Data

[ChescoWx]

6 hours ago, chubbs said:

Nope. The Chesco COOPs cool significantly relative to the SE PA Division data from the PA climatologist. Regression isn't a good tool because the station changes are sudden not gradual and you picked an interval that started after the initial Coatesville move and ended before the West Chester move took full effect. If you widen the interval to 1941-1975, the difference in slope is large.

Per table below, comparing the five years before the first move and the five years after the last move, the Chesco COOPs cool by 1.7F relative to the SE Pa Division. Note that the Pa SE Division includes the Chesco Coops so the two items compared are not independent. For that reason it is not surprising that the delta for the SE PA is slighly smaller than ABE. 

Funny seeing your persistent effort to dismiss what the the raw data from Chester County clearly shows.  The 3 stations each cooled significantly after the 1945-1970 moves: first Coatesville cooled relative to Phoenixville and West Chester; then Phoenixville cooled relative to Coatesville and West Chester; and finally West Chester cools relative to Coatesville and Phoenixville.  Clear as day in the raw COOP data.

 

 

All three stations cooled at statistically the same rate as the surrounding stations. Additionally, in looking closer at potential TOB adjustments one may wonder why the West Chester 2NW and Coatesville 1SW records which predominantly relied on morning (AM) observations...so one would think the Raw TOB Distortion of an AM reading captures a naturally lower minimum, meaning the raw data was technically already too cool correct? The NCEI Adjustment you would think logically would be to correct for morning bias at Coatesville and West Chester by warming the historical record. However, NCEI's automated, grid-wide homogenization algorithms actually did the opposite by applying additional sweeping chilling adjustments to both of these stations data from 1895 through 1982. 

[ChescoWx]

Of course @chubbsWidening the interval to 1941 - 1975 does not change the previous answer. Both series show a real, statistically significant cooling trend on their own — this isn't noise, and it fits the well-documented mid-century cooling that shows up across the eastern US from the 1940s into the 1970s.

Are the two trends statistically the same?

This is the more interesting question, and the answer depends on the test:

• Naive comparison (treating the two trends as independent): the difference in slopes (−0.66 vs. −0.46 °F/decade) gives t = −0.92, p ≈ 0.36 — not remotely significant. By this test they're indistinguishable.
• Paired comparison (the right test here, since both series describe the same regional weather in the same years — they're correlated at r = 0.83, so a paired test on the year-by-year difference is more powerful): the difference series trends at −0.021 °F/yr (−0.21 °F/decade), 95% CI [−0.042, +0.001], p = 0.057.

So the more rigorous test lands just on the wrong side of the conventional 0.05 cutoff — the station data cooled somewhat faster than the division average, and that gap is close to, but doesn't quite clear, statistical significance. The honest read: the two trends are not clearly, statistically different so no need to cool the raw data further as they are already a strong match.

[chubbs]

19 hours ago, ChescoWx said:

Of course @chubbsWidening the interval to 1941 - 1975 does not change the previous answer. Both series show a real, statistically significant cooling trend on their own — this isn't noise, and it fits the well-documented mid-century cooling that shows up across the eastern US from the 1940s into the 1970s.

Are the two trends statistically the same?

This is the more interesting question, and the answer depends on the test:

• Naive comparison (treating the two trends as independent): the difference in slopes (−0.66 vs. −0.46 °F/decade) gives t = −0.92, p ≈ 0.36 — not remotely significant. By this test they're indistinguishable.
• Paired comparison (the right test here, since both series describe the same regional weather in the same years — they're correlated at r = 0.83, so a paired test on the year-by-year difference is more powerful): the difference series trends at −0.021 °F/yr (−0.21 °F/decade), 95% CI [−0.042, +0.001], p = 0.057.

So the more rigorous test lands just on the wrong side of the conventional 0.05 cutoff — the station data cooled somewhat faster than the division average, and that gap is close to, but doesn't quite clear, statistical significance. The honest read: the two trends are not clearly, statistically different so no need to cool the raw data further as they are already a strong match.

Repeating what  I said above garbage in, garbage out.  Your analysis and AI's conclusion is faulty. You aren't telling AI that the Chesco COOPs are included in the SE PA climate division. You can't conclude that Chester County is the same as the non-Chesco stations if you include Chester County with the other stations. Second the regression slopes depend on the end-date. You need to include enough years before and after the moves for the station moves to be fully reflected in the regression. For the period 1941-1975 I get a much bigger difference in slopes -.69 for Chesco and only -.32 for the Division. Excluding Chester County from the Division would lower the Division slope further. Finally AI already has a Pvalue of 0.057, i.e, there is a 94% chance that Chesco is different using your faulty comparisons. Correct the errors and the P value will shrink considerably.

My biggest complaint though is that your statistical model is inadequate. Temperature observations are highly correlated across a region because all stations experience the same weather. The Chesco and SEPA stations should be very close. Instead the chart clearly shows that Chesco COOPS cool significantly vs the SEPA Climate Div. The different temperature response by the Chesco Coops is closely associated with the timing of station moves. End of story.

[ChescoWx]

AI knew the Chesco COOPs are included in the SE PA climate division but did not feel it material enough to change the statistical fact that the raw data at Chesco was cooling the same as the surrounding stations so again no need for further cooling. Plus with all those AM TOB readings at Coatesville and West Chester why didn't NCEI apply some warming adjustments? Again only non-stop chilling adjustments. 

[ChescoWx]

A member asked for an analysis of 100 degree days by decade since the 1890's. This is normalized as days per station per year (total 100°F+ days across all stations in a decade, divided by the number of station-years of data in that decade) rather than a raw sum — otherwise a decade with 22 stations would look "hotter" than a decade with 4 stations just from having more thermometers out there, which would be misleading.

The pattern holds up clearly at the county level, same as it did for individual stations: the 1930s stand out sharply at about 1.1 days per station per year — nearly double any other decade — consistent with the well-documented Dust Bowl-era heat. From there the rate declines fairly steadily, bottoming out near zero in the 1970s and again in the 2020s (0.01 and 0.02 days/station/year respectively), with the 2000s-2010s sitting in a modest middle range around 0.11–0.15.

Worth flagging directly: the two lowest decades in the entire 130-year record are the 1970s and the current 2020s — and the current decade of the 2020s (partial decade).

[chubbs]

18 hours ago, ChescoWx said:

AI knew the Chesco COOPs are included in the SE PA climate division but did not feel it material enough to change the statistical fact that the raw data at Chesco was cooling the same as the surrounding stations so again no need for further cooling. Plus with all those AM TOB readings at Coatesville and West Chester why didn't NCEI apply some warming adjustments? Again only non-stop chilling adjustments. 

Clear that you do not understand the science behind bias adjustments. Bias adjustments are not made in an ad hoc manner or to raise or lower the temperature of a station. Bias adjustments are only made to correct station changes. If the station observation time doesn't change, then no adjustment is needed. Adjustments are based solely on raw data. A station has to change with time in a manner that is different from all other stations that experience the same weather. The goal is to include weather and exclude station changes when calculating long-term climate trends.

The only way to evaluate bias adjustments is to inspect raw station data at the time of the station change. Here's an example using the West Chester 1970 move. The old West Chester COOP shut down in December of 1969 and re-opened in May of 1970 at a new location. Subtracting Coatesville from West Chester isolates the relative temperature changes at the two stations at the time of the move.  The raw data shows that the new West Chester site cooled by significantly relative to Coatesville after the move. That's all the proof needed to identify a major station change at either Coatesville or West Chester.  We know from raw data from Phoenixville that West Chester is the guilty party. The Chesco raw data clearly shows that West Chester cooled significantly after its 1970 move.

The NOAA bias adjustment is in complete agreement with the raw data from Coatesville and West Chester.  That shouldn't be surprising. NCEI is using all the raw data that experiences the same weather as West Chester, hundreds of stations potentially. I've looked at multiple large station changes at the Chesco COOPs and NCEI nails every one.

Note that NCEI is asking a similar question as your AI analysis. Does West Chester respond to local May 1970 weather in the same as the other regional stations? However the NCEI procedure is much more targeted than AI, is using more data, and it is using the right conceptual model. The temperatures at West Chester do not vary independently of the temperatures at Coatesville or other stations. This gives the NCEI analysis much more power. It can correctly flag the West Chester move as a major station change. While your AI analysis can not. 

The raw data is the final arbiter and in this case NCEI is clearly superior to AI.

 

[chubbs]

17 hours ago, ChescoWx said:

A member asked for an analysis of 100 degree days by decade since the 1890's. This is normalized as days per station per year (total 100°F+ days across all stations in a decade, divided by the number of station-years of data in that decade) rather than a raw sum — otherwise a decade with 22 stations would look "hotter" than a decade with 4 stations just from having more thermometers out there, which would be misleading.

The pattern holds up clearly at the county level, same as it did for individual stations: the 1930s stand out sharply at about 1.1 days per station per year — nearly double any other decade — consistent with the well-documented Dust Bowl-era heat. From there the rate declines fairly steadily, bottoming out near zero in the 1970s and again in the 2020s (0.01 and 0.02 days/station/year respectively), with the 2000s-2010s sitting in a modest middle range around 0.11–0.15.

Worth flagging directly: the two lowest decades in the entire 130-year record are the 1970s and the current 2020s — and the current decade of the 2020s (partial decade).

Nope no dust bowl in Chester County, just Phoenixville with a bad shelter location. Philadelphia and West Chester don't agree at all with your plot. Not surprising since once again you are confounding station changes and weather. East Nantmeal and West Grove are a little different than the City of Coatesville or West Chester don't you think? 

[ChescoWx]

I also carved out Phoenixville in the 2nd chart based on concerns from @chubbs it's more urban location may skew the data. With or without Phoenixville the trend is clearly toward less 100 degree days in Chester County PA.  

 

[donsutherland1]

For an illustration on how Phoenixville has changed over time (Source: Berkeley Earth):

These changes mean that simply using raw data across time creates an "apples-to-oranges" comparison when it comes to data integrity.

Notice the larger difference in warming trend between the raw data and region and much closer figure between the breakpoint-adjusted data and the region.

That's very close to the observed warming for Chester County and Pennsylvania for the 1895-2025 period:

The raw data (0.11°C/century) is the clear outlier. That divergence from the regional and statewide data illustrates the flaws in treating a station's record identically despite breakpoints, station moves, etc.

 

[ChescoWx]

5 hours ago, donsutherland1 said:

For an illustration on how Phoenixville has changed over time (Source: Berkeley Earth):

These changes mean that simply using raw data across time creates an "apples-to-oranges" comparison when it comes to data integrity.

Notice the larger difference in warming trend between the raw data and region and much closer figure between the breakpoint-adjusted data and the region.

That's very close to the observed warming for Chester County and Pennsylvania for the 1895-2025 period:

The raw data (0.11°C/century) is the clear outlier. That divergence from the regional and statewide data illustrates the flaws in treating a station's record identically despite breakpoints, station moves, etc.

 

I removed Phoenixville and no statistical change to the raw data at all!!

[ChescoWx]

So let's look at a single station with long term data 1894-1982 Coatesville 1SW. I performed an analysis of that station to see if TOB bias was part of the adjustment for 77 of 78 years of cooling data that we have documented many times before from the raw actual data. I evaluated all of the changes in observation times for the entire period of record. Of note from 1946-1982 the station observed a consistent 8am reading whhich sits close to the −0.15°C (cool bias) end of the curve, meaning the TOBS-correct move would be to add temperature back (a small positive adjustment) — yet the actual 1946-82 adjustment stayed negative on average (−0.83°F). That's a clear red flag in the NCEI adjustments as TOBS alone would predict the sign should have flipped positive after 1946, and it didn't. So without TOBS alone there remains a clear and significant leftover unexplained cooling of roughly -1.1 to -1.8°F in every single period — evening, dual, and morning alike. That's the thing that needs a separate explanation, since TOBS alone doesn't account for it. So we have seen @chubbs likes to often say that station movements tied to Coatesville's industrial history and station moves impacted the data and made it critical to chill the old data. The problem that NCEI and Charlie has is that in reality Coatesville was home to Lukens Steel — a continuously operating steel mill since 1810, one of the largest specialty steel producers in the country, still headquartered there through 1982 and beyond this is a station within a mile of significant industrial activity! This of course is a textbook candidate for a persistent local warm bias — waste heat, paved/industrial surfaces, altered local airflow. But here's the problem for NCEI and Charlie to address -  this doesn't match the data adjustments made by NCEI. The facts are that Lukens was arguably at its industrial peak in the postwar decades (1946–82) — yet that's exactly the period where the adjustment (and the residual) is smallest, not largest. If growing industrial heat were the main driver, the bias should have gotten worse over the 20th century, not better. So it is not TOB adjustments and clearly not site moves behind these adjustments so what say you Charlie?

[donsutherland1]

53 minutes ago, ChescoWx said:

I removed Phoenixville and no statistical change to the raw data at all!!

Coatesville 1SW has a strong cooling trend in the raw data, as you observed. However, there are multiple breakpoints. Adjusting for those breakpoints brings Coatesville's trend in line with regional trends.

From Berkeley Earth:

[ChescoWx]

38 minutes ago, donsutherland1 said:

Coatesville 1SW has a strong cooling trend in the raw data, as you observed. However, there are multiple breakpoints. Adjusting for those breakpoints brings Coatesville's trend in line with regional trends.

From Berkeley Earth:

 

Don you may want to look at my last post and help answer these gaps or as you call them "breakpoints" on why on a single station basis with rigorous long term station data such as Coatesville 1SW the annual supporting data from raw to adjusted for 99.7% of years from 1895 through 1971 was chilled by NCEI. We can see it is certainly not TOB and not site moves so what is it and why can't we quantify it if the science is so transparent by year with attribution to all of the potential reasons for chilling the data basically every single year for this station. Where is the NCEI detailed file explaining this particular stations unique adjustments by year?

[chubbs]

11 hours ago, ChescoWx said:

Don you may want to look at my last post and help answer these gaps or as you call them "breakpoints" on why on a single station basis with rigorous long term station data such as Coatesville 1SW the annual supporting data from raw to adjusted for 99.7% of years from 1895 through 1971 was chilled by NCEI. We can see it is certainly not TOB and not site moves so what is it and why can't we quantify it if the science is so transparent by year with attribution to all of the potential reasons for chilling the data basically every single year for this station. Where is the NCEI detailed file explaining this particular stations unique adjustments by year?

Yes TOB is not an issue at Coatesville. The big issue is station moves and other changes. The NCDC chart below shows all the locations of the Coatesville COOP station. The station numbers increase as you go back in time: Site 1 is the newest and site 6 is the original site. The most consequential move was the last one from site 2 in the City of Coatesville to to a rural site on Doe Run Road. The pictures illustrate the change. As documented in the Chester County thread roughly 2F spurious cooling with this move. 

 

 

photos

[chubbs]

13 hours ago, ChescoWx said:

I removed Phoenixville and no statistical change to the raw data at all!!

You left in all the other station changes. Your current station population is much cooler, more rural, and higher elevation compared to the older COOPs. All the COOPs were in towns before the Coatesville post-war move.

The more I look at the Chesco COOP data the more problems I find. Per NCDC the Coatesville 1SW shelter was made of window blinds before 1902. The "window blinds" apparently produced a big spike in 100F days in 1900, which wasn't observed in West Chester or Philadelphia. After the "window blind" spike, the Coatesville 1SW data is similar to Philadelphia and West Chester with no indication of the pronounced downtrend you are showing. Once again the local raw data doesn't agree with the climate trend you are reporting. 

[ChescoWx]

 @chubbs you didn't answer my previous post  "The problem that NCEI and Charlie has is that in reality Coatesville was home to Lukens Steel — a continuously operating steel mill since 1810, one of the largest specialty steel producers in the country, still headquartered there through 1982 and beyond this is a station within a mile of significant industrial activity! This of course is a textbook candidate for a persistent local warm bias — waste heat, paved/industrial surfaces, altered local airflow. But here's the problem for NCEI and Charlie to address -  the Coatesville 1SW move explanation doesn't match the data adjustments made by NCEI. The facts are that Lukens was arguably at its industrial peak in the postwar decades (1946–82) — yet that's exactly the period where the adjustment (and the residual) is smallest, not largest. If growing industrial heat were the main driver, the bias should have gotten worse over the 20th century, not better. So it is not TOB adjustments and clearly not site moves behind these adjustments so what say you Charlie?

[chubbs]

20 hours ago, ChescoWx said:

 @chubbs you didn't answer my previous post  "The problem that NCEI and Charlie has is that in reality Coatesville was home to Lukens Steel — a continuously operating steel mill since 1810, one of the largest specialty steel producers in the country, still headquartered there through 1982 and beyond this is a station within a mile of significant industrial activity! This of course is a textbook candidate for a persistent local warm bias — waste heat, paved/industrial surfaces, altered local airflow. But here's the problem for NCEI and Charlie to address -  the Coatesville 1SW move explanation doesn't match the data adjustments made by NCEI. The facts are that Lukens was arguably at its industrial peak in the postwar decades (1946–82) — yet that's exactly the period where the adjustment (and the residual) is smallest, not largest. If growing industrial heat were the main driver, the bias should have gotten worse over the 20th century, not better. So it is not TOB adjustments and clearly not site moves behind these adjustments so what say you Charlie?

OK lets see what the raw data says. After all bias adjustments are based solely on raw data. If the the steel mill impacted the Coatesville station it would be reflected in the raw data and in the NCEI bias adjustment.  Below is a plot of Coatesville 1SW minus West Chester and the Coatesville bias adjustment (right axis). A station change at either Coatesville or West Chester causes a sudden change in relative temperature of Coatesville and West Chester. While a growing steel mill or an urban heat island in one of the towns would cause a gradual change in the difference between the two stations.

There are many large sharp changes in Coatesville's temperature relative to West Chester. These are all station changes. There is no indication of a gradual long-term trend so a large change in the steel mill impact can be ruled out. Station changes are the primary cause of Coatesville's (and West Chester's) cooling.

The Coatesville bias adjustment (right axis) tracks the raw temperature data at Coatesville and West Chester closely, capturing the each wide swing due to station changes.  The only exception to the close tracking is when West Chester had station changes: 1915, the 1920s, the 1960s and with the West Chester move in 1970. 

Both stations start out at about the same temperature in the 1890s. Between 1894 and the 1960s,  most of the chart movement is due to Coatesville station changes as West Chester experienced relatively minor station changes. After 1920 Coatesville cools relative to West Chester. The change is anything but gradual with several large swings due to station changes.  From the late 1940s to the late 1950s Coatesville is 2F cooler than West Chester. The rural Doe Run Road site is the coolest Coatesville station location. Coatesville warms by roughly 0.5F around 1960. After 1960 the main station changes are at West Chester, ending in the 1970 move which cools West Chester to down Coatesville's level.   Note that station changes can be warming or cooling, but on balance both stations cooled significantly over the period due to station changes.

This exercise is another feather in NCEI's cap. The Coatesville and West Chester raw data shows that bias adjustments are needed and accurate in Chester County.  No surprise if you have been reading the thread.

[ChescoWx]

@chubbs below is some more detailed research and some solid evidence below to find if the single station NCEI applied cooling adjustments to Coatesville 1SW are supported by surrounding stations. For site moves and TOB changes.  The final finding is that the clean evidence points to a real, still-unexplained cooling signal during at least the 1952-1982 portion of this period -- not caused by a location move or TOB change (neither was validated), Also Station relocation, across the 88-year period with usable NCEI-adjusted data (1895-1982) spanning the station's six relocations, never shows up as an independent, validated driver of any adjustment on its own. Once the confounded stations are set aside, the clean evidence actually points toward a real, unexplained cooling trend during at least the 1952-1982 portion of that period — just not one caused by a location move or TOB change. Take a look at the below and let me know what this analysis is missing? This is only for Coatesville 1SW raw vs the NCEI adjusted for that individual station. Based on this I will look to see if the other NCEI station adjustments to the raw data are valid and supported by the data. I have much more supporting data so feel free to ask and I will provide more data.

Coatesville 1SW: Overall Testing Approach and Findings
Overall Testing Approach
1. Pulled Coatesville 1SW's exact location and observation-time history from NCEI's HOMR database -- six site relocations and five distinct observation-schedule eras spanning 1888-1982, independently verified against the live HOMR page and a user-provided satellite image of the final site. 2. Initially tested using NCEI's own adjustment as the yardstick (comparing how the adjustment changed before/after each documented event). This is where standard time-of-observation-bias (TOB) theory first looked promising, then broke down: an all-morning schedule (1946-1982) should need little or no adjustment under TOB theory, not the sustained cooling actually applied. 3. Switched to raw-data-only testing -- the methodologically correct approach, since testing against NCEI's own output can't establish whether that output was justified in the first place. For each of Coatesville's 7 documented events, compared Coatesville's raw record against every available nearby raw-data station in clean, non-overlapping before/after windows. 4. Required cross-validation across independent references -- an event only counted as a real, validated discontinuity if multiple neighbor stations agreed on the direction of the shift, not just one. This is the key filter separating genuine breaks from ordinary weather noise. Expanded from 2 to up to 4 reference stations (West Chester 2 NW, Phoenixville 1E, Kennett Square, Sadsburyville) depending on era. 5. Result: only 3 of 7 documented events passed. 1916, 1922, and 1946 showed real, multi-station-confirmed shifts. 1902, 1910, 1930, and 1948 did not -- either unconfirmable (no second reference available) or references actively disagreeing (the signature of noise, not a real break). 6. Built a raw-justified adjustment chain using only those 3 validated steps, anchored to the stable, unchanged 1946-1982 era as a zero baseline, and compared it decade-by-decade against NCEI's actual adjustment, with formal significance testing at each step.
Overall Finding
NCEI's adjustment ran colder than the raw evidence supports in every single decade from the 1890s through the 1980s, with no exceptions. Restricting to the 8 complete decades (1900s-1970s), 6 of 8 reach conventional statistical significance (1900s, 1910s, 1930s, 1940s, 1950s, 1960s); the other two (1920s, 1970s) don't reach significance individually but still point the same direction. Pooled across all 88 years, the effect is overwhelming (p < 0.0001). The size of the over-cooling does not trend over time -- it is a persistent, roughly steady bias, not something that worsened or improved across the record. See "Raw vs NCEI vs Corrected Trend" for the full year-by-year data, decade table, and significance tests.
Adjustment Broken Out by Rationale (all 7 documented events)
Of NCEI's stated PHA rationale categories, only station relocation and observation-time change could be directly tested here. Only 3 of the 7 documented events show real, cross-validated evidence.
Event	Rationale Category	Validated?	Contribution to the Adjustment Chain
1902	Location move	No -- single reference, unconfirmable	0 (no independent step; folded into the 1902-1915 era)
1910	TOB change	No -- 2 references disagree in direction	0 (no independent step; folded into the 1902-1915 era)
1916	Location move + TOB shift (simultaneous)	Yes -- 4 references agree	+0.36°F, partially OFFSETTING (applies to 1902-1915 only; can't attribute to either cause alone)
1922	TOB change (location unchanged)	Yes -- 3 references agree	-1.28°F, the entire step applied to 1922-1945
1930	Location move	No -- 2 references disagree in direction	0 (no step between 1922-1945 and 1946-1982)
1946	TOB change (location unchanged)	Yes -- 2 references agree (thin sample)	Combined with 1922: the entire -2.11°F applied to 1916-1921
1948	Location move	No -- 2 references disagree in direction	0 (1946-1982 treated as one continuous baseline era)
PRACTICAL ANSWER: of all 7 documented events, only 3 (1916, 1922, 1946) show real, cross-validated raw discontinuities -- 2 of those 3 (1922, 1946) are TOB changes with no location change; the third (1916) is an inseparable combined event. The 4 location-related events (1902, 1910, 1930, 1948) show no validated evidence at all. Station relocation, across the 88-year period with usable NCEI-adjusted data (1895-1982) spanning the station's six relocations, never shows up as an independent, validated driver of any adjustment on its own.
Important: What "TOB" Explains Here, and What It Does Not
The "TOB" label in the table above explains why the RECONSTRUCTED adjustment chain steps DOWN between eras (e.g. why 1922-1945 sits 1.28°F below the 1946-1982 baseline) -- it describes validated ONE-TIME transitions in Coatesville's own raw record relative to its neighbors. It does NOT mean TOB explains or justifies NCEI's actual, continued adjustment behavior within any era, including 1946-1982. If anything, classic TOB theory says a single MORNING reading (used throughout 1946-1982) should need a mild WARMING correction, not the sustained cooling NCEI actually applied that whole period (-0.82°F in the 1950s down to -0.21°F in the 1980s). That makes NCEI's continued cooling during 1946-1982 LESS justified under TOB theory, not more -- see "No Basis Found for Any Cooling Adjustment During 1946-1982" below, which is a separate, additional finding from the step-transition analysis above, not an extension of it.
Important Caveat: What "Corrected" Does and Does Not Establish
The "Corrected" series treats the 1946-1982 era as a zero-adjustment baseline because it is the final, most stable era with no further validated events. This is a standard homogenization convention (adjust the past to match the present), but it is NOT the same as proving 1946-1982 is itself free of bias. Under classic TOB theory, a single MORNING reading (used throughout 1946-1982) should carry a mild COLD bias, not be bias-free -- meaning the true fully-corrected record might need the entire chain shifted warmer, including the baseline era, which would make the required cooling for the earlier eras SMALLER than calculated here, not larger. This analysis establishes the RELATIVE size of each validated step; it does not establish an absolute, bias-free zero point.
No Basis Found for Any Cooling Adjustment During 1946-1982
Separately from the baseline-anchoring question above, a cleaner and more direct claim: within the 1946-1982 period itself, location and observation schedule were BOTH stable throughout (no validated events of either kind). An additional check for undetected drift WITHIN this period (not just at its boundaries), using every available overlapping reference station, found no consistent evidence either: Devault 1W and Morgantown each show a significant COOLING drift relative to Coatesville (-1.15 and -0.26 F/decade), while West Chester 2 NW shows a significant WARMING drift in the OPPOSITE direction (+0.52 F/decade), and Phoenixville 1E shows no significant drift at all. By the same cross-validation standard used throughout this investigation, this disagreement means no validated drift exists either. CONCLUSION: with no validated location change, no validated TOB change, and no validated drift anywhere in this 36-year window, there is no raw-data basis found for ANY of NCEI's cooling adjustment during 1946-1982 -- not the varying decade-by-decade amounts NCEI actually applied (ranging from -0.82°F in the 1950s to -0.21°F in the 1980s), and not a flat adjustment either. This covers what could be directly tested here -- station moves and TOB, two of NCEI's four stated PHA rationale categories. No evidence of an undocumented instrument or land-use change was found either, but the available data could not specifically rule those out.
Reference Station Confound Check (added later)
The cross-validation method above assumed the reference stations (West Chester 2 NW, Phoenixville 1E, Kennett Square, Sadsburyville, Devault 1W, Morgantown) were themselves stable during the windows used to test Coatesville. Checking each one's own HOMR history directly found this was not fully true.
Reference Station	Own HOMR History	Confound Found?
West Chester 2 NW	Moved slightly in early 1921; further moves in 1936, 1955, 1970, 1998, 2009, 2016	YES -- 1921 move overlaps the 1922 test's "before" window (1918-1921); 1955/1970 moves fall inside the 1946-1982 interior-drift window
Phoenixville 1E	Stable 1915 to 1948-05-01, then moved	PARTIAL -- clean for 1922/1930/1946; its 1948 move falls inside the 1946-1982 interior-drift window
Kennett Square	Moved between 1916-11-30 and 1919-01-01	YES -- overlaps the 1916 test's "after" window (1917-1920)
Sadsburyville	Single location, entire 1910-1922 operating life	None -- clean
Devault 1W	Single location, entire 1951-1989 operating life	None -- clean
Morgantown	Single location, entire 1951-1987 operating life	None -- clean
REVISED CONCLUSIONS: (1) The 1916 finding still holds -- Sadsburyville (fully clean) and West Chester (clean for this specific window) both independently confirm it; only 1 of its 4 supporting references (Kennett Square) has a confound. (2) The 1946 finding is unaffected -- both its supporting references were stable throughout that specific window. (3) The 1922 finding is WEAKER than originally presented: it only ever had 2 supporting references, and the West Chester one is now known to be confounded by West Chester's own 1921 move. Phoenixville alone remains clean and still shows the same direction, but that is one clean reference, not the two-station cross-validation required elsewhere in this analysis -- treat 1922 as a lower-confidence, single-reference finding, not a fully cross-validated one. (4) MOST IMPORTANTLY, this partially reverses the "No Basis Found for Any Cooling Adjustment During 1946-1982" conclusion above: the earlier interior-drift check found 4 references disagreeing and read that as noise, but 2 of those 4 (West Chester, Phoenixville) turned out to have their own undocumented moves inside that exact window, while the 2 clean references (Devault 1W, Morgantown) both agreed on a real cooling drift (-1.15 and -0.26 F/decade). Once the confounded stations are set aside, the clean evidence points to a real, still-unexplained cooling signal during at least the 1952-1982 portion of this period -- not caused by a location move or TOB change (neither was validated), but a genuine physical signal nonetheless, not simply noise as previously stated.