ChescoWx

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.

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.

Plenty of lows in the 50's this morning with the lowest being 50.3 degrees at the Warwick DEOS station. Today will be the 10th below average temperature day over the last 15 days. We should continue to see below average temperatures for what is, on average, our warmest week of the year for the rest of this new work week. A beautiful day today with some ridge locations remaining just below 80 degrees. Rain chances increase toward tomorrow morning with the general forecast being for between 3/4 and an inch of rain for most spots with showers lasting till Wednesday AM. We dry out and stay cool on Thursday with highs only in the mid 70's - almost 10 degrees below normal levels for late July.

Plenty of lows in the 50's this morning with the lowest being 50.3 degrees at the Warwick DEOS station. Today will be the 10th below average temperature day over the last 15 days. We should continue to see below average temperatures for what is, on average, our warmest week of the year for the rest of this new work week. A beautiful day today with some ridge locations remaining just below 80 degrees. Rain chances increase toward tomorrow morning with the general forecast being for between 3/4 and an inch of rain for most spots with showers lasting till Wednesday AM. We dry out and stay cool on Thursday with highs only in the mid 70's - almost 10 degrees below normal levels for late July.

So we did a little fact check on Charlie's claim that the raw data cooled more than surrounding stations.....The facts are that the raw cooling data is well supported by the surrounding regions! Below is the AI review of the raw data for the 3 stations in question. What that regional record shows for 1946–1970 Using Penn State's State Climatologist office data (built from this same NCEI divisional dataset): Metric Official SE PA Division (Chester/Berks/Montgomery/Lancaster region) Your 3-station Chesco composite 1946 annual avg 54.0°F — 1970 annual avg 52.4°F — Trend −0.093°F/yr −0.083°F/yr Total change, 1946–1970 −2.23°F −2.00°F R² 0.365 0.352 p-value 0.0014 0.0018 That's a remarkably close match — both in direction, magnitude, and statistical significance. Individually, Phoenixville 1E (−2.34°F, p=0.0008) and West Chester 2NW (−2.48°F, p=0.0014) track the regional figure almost exactly; Coatesville 1SW is a bit weaker (−1.17°F) and only marginally significant on its own (p=0.055), but still points the same direction. Bottom line: Yes, the cooling is well supported by the surrounding region. This is a case where the "raw" county data and the "official" broader regional data agree closely So @chubbs if the cooling in the raw data is statistically the same as the surrounding data why did NCEI choose to chill the raw data further in each and every year between 1946-1970??

In the below 2022 study, "the authors analyzed thousands of different versions of the dataset downloaded over 10 years. They studied the homogenization adjustments for more than 800 European temperature records. They found that these adjustments changed dramatically every day when NOAA re-ran their computer program. The authors found that only 17% of NOAA’s adjustments were consistent from run to run. Furthermore, by compiling historical records known as station history metadata for each of the stations, they were able to compare the adjustments applied by NOAA’s computer program to the documented changes that were known to have occurred at the weather station. They found that less than 20% of the adjustments NOAA had been applying corresponded to any event noted by the station observers - such as a change in instrumentation or a station move." Homogenization of data is badly flawed and should be disregarded as such"The study itself was not focused on the net effects of these adjustments on long-term climate trends. However, the authors warned that these bizarre inconsistencies in this widely-used climate dataset are scientifically troubling. They also are concerned that most researchers using this important dataset have been unaware of these problems until now.https://www.ceres-science.com/post/major-problems-identified-in-data-adjustments-applied-to-a-widely-used-global-temperature-dataset?fbclid=IwY2xjawTJxvZleHRuA2FlbQIxMABicmlkETFRaGlnYzJQQVNzdndoTkdwc3J0YwZhcHBfaWQQMjIyMDM5MTc4ODIwMDg5MgABHlguzGDpWxHyS0ptciE_1okX3LFV-2pBe4Pu2WQnleZLxvskMdPVhhDxQZq5_aem_g_cHQVsBuo4BwgjgPPTV1g

So I asked AI to review the Chester County PA raw data set since 1893 to find if there is a significant p-value that shows warming in this County. The AI review of the data finds clearly that No — the raw Chester County composite does not show a statistically significant warming trend since 1893. The numbers (1893–2025, 133 years) Linear trend: +0.0043°F/year (≈ +0.43°F per century) 95% confidence interval: −0.0012 to +0.0097°F/year — this interval includes zero, which is the definition of "not significant" R² = 0.018 (the trend line explains less than 2% of year-to-year variation) p = 0.128 — above the conventional 0.05 threshold A robust version of the same test (Theil-Sen, less sensitive to outlier years) gives essentially the same answer: +0.40°F/century, still not significant So statistically, you can't distinguish this composite from a flat line over 133 years. Only if we allow NCEI post hoc alterations and adjustments to the raw data can we glean any signifcant p-value warming across Chester County PA! This is how folks lose trust in data when only with post hoc adjustments can we show any significant warming in our climate since 1893!