ChescoWx

Mike, I'll take your four questions in order Q1 - yes. Raw records could potentially carry non-climatic biases that don't cancel but not always! Q3 - yes. Williams 2012, Venema 2012 and Killick 2022 are real, adversarial, and they show homogenisation reduces error if a station has proven data issues, I accept that and I'm not going to pretend the literature says otherwise. Q2 - one correction. You say breakpoint detection is "even unstable run-to-run (shown in this thread's own evidence)." It wasn't shown. I went looking for it: two pulls of the West Chester QCF taken a few years apart were identical across all 119 complete years, unadjusted series identical too. NCEI told me the output can change daily; I tested it and found none over that interval. That concession isn't mine to accept. Q4 is where we really differ, and it's about scope. My claim is narrower: the specific magnitudes applied to specific Chester County stations haven't been independently verified, and showing an event occurred doesn't verify the size of the correction attached to it. The benchmarks measure whether homogenisation moves a NETWORK closer to truth on average - the right quantity for a national series, and a different question from whether one station in one decade got the right number. Venema's own write-up notes it modelled small European networks at high station density without network-wide trend biases; Williams found improvement in the presence of widespread systematic errors. Both are aggregate statements under stated conditions. The conditions matter here. Before 1951 this county has three continuous stations. Menne and Williams say it themselves in the 2009 paper: false alarms at neighbouring stations reduce the number of homogeneous neighbours and thereby prevent the estimation of adjustments. That's the sparse-network failure mode described by the algorithm's own authors, in the era carrying the largest adjustments. On cherry-picking - you introduced Coatesville as the exemplar and called it two resounding yeses. If it's representative enough to validate, it's representative enough to examine. You asked for a case. Here's the beginning of one, and it's a magnitude test rather than an occurrence test. So I built a regional reference for Coatesville from the raw, unadjusted Chester County records only - leaving Coatesville 1SW out so that it never contributes to its own comparator, and no homogenised product anywhere in the calculation. Measured drift of Coatesville against those raw neighbours over 1895-1982 is -0.190 F/decade using every available station, or -0.113 F/decade using a fixed panel that can't change membership. The applied NCEI adjustment runs +0.303 F/decade, which implies a drift of -0.303. That value falls outside the 95% confidence interval of the measured drift under both reference constructions. The adjustment also tracks the drift year to year - r = -0.74 - so it's aimed at something real. It's the size I'm questioning, not the existence. What this is so far in all of my multiple years of review which has been my analytic goal of this process of reviewing the adjustment of raw data at one targeted station Coatesville 1SW is that the correction appears larger than the divergence it corrects, measured without using any homogenised data. If that's wrong I'd like to know how?? Paul

Mike, those aerials are genuinely useful and I'm glad to have them. They establish something I'd have had a hard time establishing myself: that the site was disturbed, repeatedly, across that whole period. I'm not disputing that. But again they just don't get you to either of the two claims you're making. Documenting that something happened at a site is not the same as documenting how much it changed the temperature, or in which direction. The aerials show construction. They don't measure its thermal effect. Every step magnitude in the NCEI record was sized by neighbor comparison, not by anything visible in a photograph, and that is the number that has to be right for the correction to be right. And there's a direction problem I raised earlier that I have not heard you answer or reconcile. An electrical substation with megawatts running through it, accumulating buildings and hard surfacing from 1946 through 1982, that is clearly a warming influence on the raw record. Correcting a progressive warming bias means pushing the later data down or cooler relative to the earlier. NCEI's correction goes the other way - the two NOAA changepoints in that window are +0.45 F at 1959 and +0.95 F at 1971, net +0.40 F, raising the later data, and the overall adjustment lifts the modern era relative to the early one. You do offer a second mechanism - that the station itself may have moved as office space changed. If it moved away from the heat sources, that would produce cooling steps needing a warming correction, and the sign would work. But that's the opposite mechanism from the one the aerials show, and it's offered as a possibility rather than as something documented. Both can't be driving the same window. Which one do you think it is, and in which years? The other thing that doesn't sit right: if construction were producing stepwise changes throughout 1952-1982, I'd expect the detectors to be finding them. NOAA places two changepoints in that window. Berkeley places five, and by your own figure they come to about -0.10 F net across seventeen years. That's a lot of documented disturbance producing very little net correction. So where I see us in reality standing on this analysis is on validity: showing that an event occurred does of course not validate the size of the correction applied to it. That would take an independent measure of the effect, and I don't think you have so far produced one yet - yours truly also! Of clear necessity: demonstrating that the adjustment is essential requires showing the uncorrected data gives the wrong climate answer, which requires knowing the right answer independently. Neither of those has been establish here. I'm not claiming the adjustments are wrong. I'm saying "documented" and "validated" are different words, and the work so far has established the first, not the second. If you have something that speaks to magnitude rather than occurrence, I'd genuinely like to see it. But again we are far away from any proof you claim to see!

What remains genuinely open regarding Coatesville 1SW remains the magnitudes have never been independently checked. A documented 0.3-mile move does not actually tell us the offset should be +0.86 °C. That number comes from neighbor comparison, not from the site. Nobody in this thread has tested whether the applied steps match what the physical changes would produce. Also of note about a third of the adjustment trend attaches to no listed changepoint at all. +0.123 reconstructed against +0.184 actual. No station history can validate a component that no documented event is claimed to explain, and NCEI hasn't yet answered that from my earlier email. Lastly, and what can't be overlooked is that the raw cooling doesn't behave the way the artifact explanation predicts. Fitting the breaks actually deepens it rather than dissolving it!!

Not so fast Mike!! We are not close yet to what think is being answered! The deep dive above clearly has not yet answer these two questions for Coatesville! First the refit I promised with some very important findings!! and then where I think you and I are answering different questions. At the end I will address your Phoenixville box above. I said I wouldn't quote that 1952-82 trend until I'd refit it against the full break set, because if there are several real discontinuities in the window then a single-step model is under-specified and the number is worthless. I've now done it, and the result is quite surprising!! The mechanism first, because it's the interesting part. A step term and a trend term compete for the same variance in a regression. If Coatesville's apparent cooling were really just the station stepping down at a few dates, fitting those steps should soak up the drop and leave the residual slope flattened toward zero. That is exactly the test. But what actually happened is the complete reverse. Every fitted step comes out positive - the model wants the later years lifted, not lowered - and lifting the later years forces the underlying line to fall more steeply to still pass through the data. Coatesville 1952-1982, annual, trend and steps estimated jointly in one model rather than subtracting steps first: no steps -0.594 F/decade p = 0.0001 1973 only (my attributed break) -0.735 F/decade p = 0.0048 NOAA's two (1959, 1971) -0.959 F/decade p = 0.0272 Berkeley's five (1959/68/71/73/76) -1.657 F/decade p = 0.0188 Significant in all four. Fitted steps +0.45, +0.46, +0.89, +0.91, +0.81 F, every one positive. So the more of your documented breaks I grant, the more raw cooling is left over needing some other explanation. The weaknesses, because I'd rather flag them myself. Not one of those steps is individually significant - best p is 0.17, standard errors 0.6 to 0.7 F against steps of 0.45 to 0.91. So this isn't proof the steps are positive. It's that the data, asked where steps would sit if they exist, puts them in the direction that deepens the cooling. Suggestive, not conclusive, and it neither confirms nor refutes your documentation, because at annual resolution this series can't resolve steps that size. AIC prefers the no-steps model over every step set, though with those SEs that's weak too. And the five-break fit is badly under-powered: seven parameters on 31 values at 0.75 F residual SD detects a genuinely present trend only about 14% of the time in simulation. It found one anyway, which is why I'm reporting it rather than quietly setting it aside - it's the most favourable number to me and the one I trust least. So what I'll stand behind is a range: -0.59 to -1.66 F/decade over 1952-1982 depending on the break set assumed, significant in all four specifications. Now, on validity and necessity. I think we're answering different questions. Your work establishes that events occurred at those dates, and I've conceded that without reservation. Validity is a further step: it requires the magnitude applied at each date to be right. The PHA sizes each step from neighbour comparison, not from the site. A 0.3 mile move is a documented fact. The +0.86 C attached to it is an estimate. Nothing in the 530-1s, the deeds or the aerials tests that estimate, and that's the question I keep coming back to - it isn't answered by more documentation, however good the documentation is. Necessity is different again. If the raw cooling at Coatesville were an artifact of the station changes, fitting those changes should dissolve it. It doesn't. It deepens it!!!!. Whatever else that shows, it isn't what "the adjustment is essential to get the right answer" predicts. And about a third of Coatesville's adjustment trend isn't attached to any listed changepoint at all. NCEI's twelve cumulate to +0.123 C/decade against an actual adjusted-minus-raw trend of +0.184. Station history can't validate a component that no documented event is claimed to explain. I've asked NCEI what accounts for it rather than guessing, and I'll post their answer either way. On Phoenixville I'd want to look at your figure properly before saying much, and I'll say up front that my own analysis can't support a claim about that station in either direction. When I tested its 1952-82 trend against a step placed at every possible date, 14 of 21 rendered it non-significant. That series is too short and too noisy to separate a step from a trend, so I'm not going to argue it either way. I'd also note that if the microsite is changing continuously - your reading of the aerials is roughly every ten years from 1927 forward - then the disturbance is gradual, and a step function is an odd model for gradual drift. On the two hours: fair enough, and I've said as much. Though the changepoint list I've been working from came from NCEI directly on request, and isn't online anywhere. The offer stands on your 530-1 and deed compilation. Your dates are better than the ones I read off your figure, and the magnitude question needs them. Now regarding the last Phoenixville block - that block does not say what your post said. Your comment claims the adjustments are "valid and absolutely necessary," but the header states ten breaks now carry a documented physical cause and seven smaller breaks remain unexplained, plus one marked UNRESOLVED at 1966 and a merged box labelled "UNDOCUMENTED — 7 BREAKS." That's 10 of 18, not a resounding yes!!!! Thanks for posting it — it's a more careful figure than the summary suggests. What strikes me most is that the two sources diverge here in a way they don't at Coatesville. At 1940 — the largest documented move in the record, 2.1 miles — BEST flags +0.75 F and NOAA flags nothing at all. At 1942 it's the reverse. At 1985 you note the NOAA break is a single-station calibration artifact. If two implementations of neighbour-based detection disagree about whether the biggest documented move in the record produced a break, that seems worth more attention than either of us has given it. The 1920 entry is the strongest piece of documentary work in either of your figures, incidentally — coords changing then reverting a year later while the offset doesn't is a real finding and I'd not have got there. My own analysis cannot support the claim that Phoenixville cools — which matters because Phoenixville has been used as a comparator throughout this thread. Charlie dismissed my Coatesville–Phoenixville comparison over a 1948 break, and I cited Phoenixville's raw trend earlier in the exchange. Testing its 1952-82 trend against a step at every possible date, 14 of 21 rendered it non-significant. Too short and too noisy to separate a step from a trend, so to date we cannot find total support for these NCEI adjustments to Coatesville 1SW Paul

Kevin I can't wait for less humidity I am over it while not our hottest summer It sure feels like one of our most humid!!

Mike, this is in my view the most useful thing anyone has put in this thread, and it changes my position on several points. Thank you for doing the archival work rather than just asserting it. Taking your points in order. You're right that "undocumented" in the algorithm's metadata linkage is not the same as "no documentation exists." I was treating the two as equivalent and that was a wee bit sloppy. Your figure shows some actual events behind most of the Coatesville breaks, and the burden argument is fair — I shouldn't claim an absence of records without going through the 530-1s, the deeds and the aerials first. I hadn't. You had - thanks!. You're also right that a high rate of undocumented detections is expected from a detector built to catch undocumented changes, so the 86% figure doesn't carry the weight I was giving it. I'd already dropped that argument after NCEI sent me their changepoint list for this station — it shows 4 of 12 linked to documented events, not zero, so the Berkeley code counts were never a good proxy for what the PHA is doing. On the ramp point: Mike - you're right - many small stacked breaks produce a ramp-shaped cumulative. I proved your point without meaning to — cumulating NCEI's twelve discrete changepoints gives a series that fits a straight line at r-squared 0.495. That's a stack of steps looking smooth, exactly as you say. Zero-adjustment stations and the diurnal range point are both fair points also. A detector leaving clean stations alone is working, and DTR divergence is a studied phenomenon rather than a contradiction. And I accept that a handful of stations in one county is a noisy sample by nature. Now a couple things I will push back on a little, not on it's substance but on how firmly you state it. Your own figure marks 1920 unresolved. And I'd read the 1959-1976 group differently to the header on it. The box says five breaks, but NOAA only has two in that window — 1959 and 1971. The other three are BEST-only. And BEST's five nearly cancel: -0.50, +0.37, +0.02, +0.72, -0.71 comes to -0.10 F net across seventeen years, which isn't doing much work. NOAA's two come to +0.40 F, and that's the direction you'd correct for spurious cooling, not for a station warming under encroaching infrastructure. Which brings me to the part I can't pull together. The station moves to progressively cooler sites implies the raw acquires spurious cooling and needs the later data warmed — which matches what NOAA applied. Infrastructure growing up around the site implies the opposite. Both are in your account of this window. Which one do you think is actually driving it? For what it's worth, your 1959 and 1971 values match NCEI's changepoint list for this station exactly once converted — -0.54 and +0.94 F against -0.28 and +0.53 C. So we're working from the same PHA output, which is worth knowing! Thanks again Mike!! That window also stops something I was about to post. I ran a segmented breakpoint analysis on the raw daily data and it attributed only one concordant discontinuity to Coatesville, January 1973. I then fitted the 1952-82 trend with that single step in the model. If there are more real breaks in that window, my model is under-specified and the number isn't worth quoting. I'm going to refit it against the full break set before I use it. If it doesn't survive, I'll say so here. Stay tuned for that later! The one thing still open is narrower and comes out of NCEI's own files rather than the station history. Cumulating their twelve changepoints reproduces +0.123 C/decade of adjustment trend. The actual adjusted-minus-unadjusted trend for the same station and years is +0.184. About a third isn't in any listed changepoint. It isn't rounding, and it isn't run-to-run variation — I compared two pulls of the adjusted series two days apart and they were identical across all 119 years at West Chester. I've asked NCEI what accounts for it rather than guessing, and I'll post their answer either way. I sent the email this morning to my contact there...stay tuned for more of that later! Now my ask - would you be willing to share your compiled 530-1 and deed work for Coatesville, and whatever you have for West Chester? I'd rather build on it than duplicate it badly, and I'll take your point about the 1978, 1982 and 1988 West Chester breaks — the Daily Local should have left a trail worth chasing. Charlie, I think most of the above answers you as well. You were right that a 35-year regression is not a breakpoint test, and running it properly is what led here. On 1945-49 specifically, NCEI's list has a documented move at 1946-01 with a +0.79 C step, so something documented did happen there. I still can't test that window myself — only three Chester County stations cover 1930-1975 with continuity and attribution needs four — so at this point we can't claim it either way. Paul

Today will be our last day with higher humidity. We should cooler weather both tomorrow and especially on Saturday. However, we turn more humid and wetter again by later Sunday into Monday. Drier and near normal temperatures arrive by next Tuesday.

Today will be our last day with higher humidity. We should cooler weather both tomorrow and especially on Saturday. However, we turn more humid and wetter again by later Sunday into Monday. Drier and near normal temperatures arrive by next Tuesday.

No hand waving Mike....just no clear documented reasons as only four of 51 (8%) trace to a documented real physical cause — three moves and only one TOB change. There are 2 zero break stations that are our controls - Coatesville 2W and Hopewell demonstrate that the PHA is indeed selective as it left these 2 stations untouched: NCEI applied no adjustment to either - which proves the 14 breakpoints at Coatesville 1SW were a deliberate finding rather than a default. The Coatesville 1SW dates, all code 4: 1896-12, 1902-02, 1917-08, 1920-09, 1922-08, 1930-10, 1936-05, 1941-06, 1946-04, 1959-11, 1968-05, 1971-04, 1973-07, 1976-02. Fourteen inferred discontinuities against six documented HOMR relocations, coinciding with none of them. The linear ramp clearly fits far better than any step. And when you allow both, the step collapses to −0.050 °C while the slope survives essentially intact at +0.182 °C/dec. A one-time convention change explains basically none of it. And more importantly the actual magnitude is out of range. The Coatesville adjustment swings +1.51 °C from first decade to last (West Chester, from NCEI's own file, swings +2.38 °C). Published TOB corrections for a full afternoon-to-morning switch run roughly 0.2–0.5 °C in annual mean. So TOB, even granting it entirely (which is not valid), accounts for perhaps a third of the Coatesville adjustment and a fifth of West Chester's. To summarize how it all fits together Mike: Raw agreement across stations. Coatesville 1SW −0.366, West Chester 2NW −0.409, Phoenixville 1E −0.339 over 1941–75, all p ≤ 0.0012, inside each other's error bars. Both systems erase it. Berkeley and NCEI each render all three non-significant, with adjustment trends correlating at r = 0.9986. The correction is a "smooth ramp" which you question above but certainly not a step — which no single documented event can explain. Its size exceeds TOB by 3–5×. The breakpoints lack documentation. Fourteen at Coatesville, all code 4, against six documented relocations in HOMR. At West Chester, April 1921 and November/December 1927 are documented observer-and-site changes classified as empirically detected, and the March 1936 relocation produced no breakpoint at all. Phoenixville is the cleanest case — no detected convention change anywhere in its record, and it still cools at −0.339 (p=0.0012) - why is that? So many questions and still so few answers!! The unanswered questions that follows from this is narrow and should be answerable: exactly what documentation supports the fourteen breakpoints at USC00361589 - Coatesville 1SW and what portion of the adjustment at Coatesville is attributed to time-of-observation versus other causes? That last question is the one they can't deflect — because the shape of their own adjustment says it isn't mostly TOB because if TOB was factored in it would actually be supporting a warming not a cooling adjustment at Coatesville!

You will often here folks say well while our average daytime highs may not be warming significantly....we are certain that the nightime lows are warmingg....Well I went back and did a statistical analysis to see if between 1890 and 2025 we saw statistically warming of overnight lows and daytime highs along with the overall average temperatures. We used both a pure raw all station mean which is just the raw untouched data and an anomaly composite which while still raw data, treats each individual station referenced to its own baseline so the changing station roster and locations can't fabricate some false trend. Raw all-station mean (the literal, unadjusted county average): none of the three are statistically significant. Average high: +0.055 °F/decade, p = 0.073 — warming, but just short of significance (borderline). Average low: +0.022 °F/decade, p = 0.49 — not significant. Overall average: +0.039 °F/decade, p = 0.15 — not significant. So by the pure raw mean, there's no statistically significant warming or cooling in any of the three over 1890–2025 — a slight (non-significant) warming lean in all three. Anomaly composite (still raw data, but each station referenced to its own baseline so the changing station roster can't fabricate a trend): two of the three are significant, and they point in opposite directions. Average high: +0.094 °F/decade, p = 0.003 — significant warming. Average low: −0.075 °F/decade, p = 0.008 — significant cooling. Overall average: +0.010 °F/decade, p = 0.72 — not significant (the high and low cancel out). The one thing both methods agree on firmly: the overall average temperature shows no statistically significant trend either way across the 135 years across Chester County from 1890-2025. Below are some charts that highlight all of the above.

Hi Mike I did of course supply all of the above information to Claude to ensure we got a useful result! As you know homogenization remains nothing more then a hypothesis-driven statistical correction, it is of course not a measurement. Pairwise algorithms like PHA infer breakpoints from neighbor differences, and when 44 of 51 Berkeley breakpoints at Chesco stations are a code 4 meaning empirically detected, with absolutely no metadata backing, that's an algorithm asserting station changes that are clearly not able to be documented. That is a legitimate target for scrutiny, it is not fringe skepticism. My finding that the adjustment series itself carries a significant linear time trend (r² 0.34–0.67) is the greatest point I have — a correction for discrete, random station artifacts shouldn't behave like a smooth ramp as these adjustments do!

Back to the NCEI adjustments Station Breaks Code 1 (documented move) Code 2 (gap) Code 3 (documented TOB) Code 4 (no documentation) Coatesville 1SW 14 0 0 0 14 West Chester 2NW 10 2 0 1 7 Phoenixville 1E 9 0 1 0 8 Devault 1W 5 0 0 0 5 West Chester 1W (Hadley) 5 0 1 0 4 Kennett Square 4 0 1 0 3 Coatesville 2W 2 1 0 0 1 Morgantown 2 0 0 0 2 Sadsburyville 0 — — — — West Grove 1SE 0 — — — — TOTAL 51 3 3 1 44 Four of 51 breaks (8%) have a documented physical cause. Forty-four (86%) are statistically inferred with no documentation. And yes — the two systems agree at r = 0.9986, mean difference 0.030 °C/decade across the five stations NCEI adjusted. That's the bridge I failed to draw last message. Put together, the argument runs: NCEI's files publish no breakpoint information at all — I checked every field; there's no changepoint list, no dates, no reasons. But NCEI's adjustments are near-identical to Berkeley's, and Berkeley does publish the reasons. So Berkeley's inventory is a defensible proxy for what the PHA is doing to the same stations. And that inventory says: overwhelmingly undocumented, statistically inferred corrections. Coatesville 1SW is the clearest case — fourteen breakpoints, every one empirical, against six documented relocations in HOMR. The algorithm found fourteen discontinuities and matched none of them to a known event. Meanwhile at West Chester it did the reverse error: classified the April 1921 and Nov/Dec 1927 documented observer-and-site changes as empirical, and produced no breakpoint at the documented March 1936 relocation. So the metadata is being used badly in both directions — real events missed or mislabelled, inferred events unsupported. Now "undocumented" is not the same as "wrong" — we know the PHA is designed to catch undocumented changes, and station histories are genuinely incomplete. But the specific issue at Coatesville 1SW remains that 86% is a high proportion on which to rest a correction that reverses the sign of Coatesville's trend, and it's a fair thing to put in front of them: on what basis were fourteen breakpoints identified at a station with six documented relocations, none of which they coincide with? I have drafted an email that I have sent to them this AM see below and I will keep you updated. Jared -Thank you again for the QCU and QCF files — they were exactly what I needed. Working through them raised a question I don't think the distributed product can answer, and I'm hoping you can point me to whoever handles PHA methodology. The GHCN-M v4 records carry ID, YEAR, ELEMENT and twelve repetitions of VALUE/DMFLAG/QCFLAG/DSFLAG. As far as I can tell there is no changepoint list, no adjustment magnitudes, and no indication of what supports any given correction. For USC00369464 (West Chester 2NW) the QCF series applies roughly -2.37 C to the 1855-1869 period — a stretch covered by a single observer at a single site, per WB Form 530-1, Index No. 36-9464-3. For USC00361589 (Coatesville 1SW) and USC00369464 (West Chester 2NW), could I request for the entire POR: 1. The changepoint dates the PHA identified for each station. 2. The adjustment magnitude applied at each changepoint. 3. Whether each was supported by documented station-history metadata or detected statistically from neighbor comparison and if so what station(s) were used for this neighbor comparison? I understand the PHA is designed to detect undocumented discontinuities, so I'm not assuming documentation exists for every break — I'd simply like to know which are which. Berkeley Earth publishes exactly this per station (a per-month code distinguishing documented moves, time-of-observation changes, gaps, and empirical detections), which is what prompted the question. If this is better directed elsewhere within NCEI, I'd be grateful for the referral. Thanks very much, Paul

Our muggy warm weather looks to continue through tomorrow with chances of showers and thunderstorms before a cold front crosses the area by later Thursday. Following that front we get an almost autumnal sneak peek with highs Friday through Monday in the upper 70's to around 80 degrees and lows by Saturday morning in the refreshing 50's.

Our muggy warm weather looks to continue through tomorrow with chances of showers and thunderstorms before a cold front crosses the area by later Thursday. Following that front we get an almost autumnal sneak peek with highs Friday through Monday in the upper 70's to around 80 degrees and lows by Saturday morning in the refreshing 50's.

Below is the climate summary for West Chester for the decade of the 1870's with data now back to 1871