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.

One last great weather day before we turned unsettled and wet for a good part of the upcoming work week. Hopefully, most of us see some rain as many spots, especially across Northern Chester County missed the rains last week. Below normal temperatures look to continue all week but with increasing humidity with the rain. The sun looks to it will return by Friday. Note: below on the climate records there is an errant snow report in the data set that is being corrected.

One last great weather day before we turned unsettled and wet for a good part of the upcoming work week. Hopefully, most of us see some rain as many spots, especially across Northern Chester County missed the rains last week. Below normal temperatures look to continue all week but with increasing humidity with the rain. The sun looks to it will return by Friday. Note: below on the climate records there is an errant snow report in the data set that is being corrected.

@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?

Another chilly start for much of the area again today with the Warwick DEOS as low as 48.6 degrees this AM. A great weather weekend on the way with highs from the upper 70's to low 80's and lows in the 50's to low 60's. Rain chances look to increase both Monday and Tuesday - there could be some heavy rain chances for the area.

Another chilly start for much of the area again today with the Warwick DEOS as low as 48.6 degrees this AM. A great weather weekend on the way with highs from the upper 70's to low 80's and lows in the 50's to low 60's. Rain chances look to increase both Monday and Tuesday - there could be some heavy rain chances for the area.

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?

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?

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

Plenty of low temperatures in the 50's this morning with the Warwick DEOS our usual chilly spot at 51.8 degrees. One of the best stretches of weather we have seen in quite a while is underway. Below normal temperatures ranging from the upper 70's to low 80's with lows in the 50's to near 60 degrees through the weekend and into the start of next week. Next chances of any showers looks to be Monday night.

Plenty of low temperatures in the 50's this morning with the Warwick DEOS our usual chilly spot at 51.8 degrees. One of the best stretches of weather we have seen in quite a while is underway. Below normal temperatures ranging from the upper 70's to low 80's with lows in the 50's to near 60 degrees through the weekend and into the start of next week. Next chances of any showers looks to be Monday night.

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.

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).

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.

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.