TheClimateChanger

A little deeper dive in the Chester County temperatures over the past 18 years. Maybe @chubbshas an explanation. I calculate a warming trend of 12.64F/century at the U.S. CRN station located at Avondale 2N, a warming trend of 12.13F/century at PHL Airport, a warming trend of 11.14F/century at @ChescoWx's East Nantmeal location. Yet NCEI only reports a warming of 7.99F/century. According to data supplied by @ChescoWx, other stations he analyzes (varying sites) show a warming of 6.91F/century over this timeframe when averaged together. It looks to me like NCEI is underdoing recent warming, when the gold standard CRN station is showing so much warming, supported by PHL's data and @ChescoWx's high quality backyard data. I suspect actual warming could reach 15-20F/century over the coming decades before plateauing.

Thank you! I wouldn't say that's an insignificant difference, no? The two highest quality stations (Avondale and East Nantmeal) with data available over the entire period show a warming trend of 12.64F/century and 11.14F/century respectively over that time frame, while the others show a warming trend of 6.91F/century. That's nearly half as much warming. Chester County is very fortunate to have a USCRN station. With the official ChescoWx (TM) index deviating so much from the CRN data [especially when it's largely corroborated by your own temperature data] just over the past 18 years, isn't that a concern?

Can you post the mean temperatures for each year as in the original graphic for EN and Avondale?

Well, can we see it? This would be a good test of the validity of the official ChescoWx temperature index over the past couple of decades. We'd have a USCRN station, your own gold standard East Nantmeal data, and then the official ChescoWx county-wide average for 2007-2024.

Can you do an overlay of these two stations, plus your full Chester County dataset over the same timeframe (2007-present)?

I can give you a clue. The period before 1970 was the twilight of relative climate stability. CO2 levels rose about 30 ppm between 1895 & 1969. They have risen another 100 ppm since then.

Several of those threaded records have large jumps in elevation, and many go from city center to suburban even rural. With even the stations outside of the bigger cities having significant biases. Regardless, again, you feel the need to interject with "context" unrelated to my original post. Here is the full Ohio dataset for January. There is a small cooling trend from 1895-1969 of about 0.5F/century. Since 1970, it's warming at a rate of 10.1F/century, and even higher than that in the northern parts of the state. Grafted together, yes, it looks like there's not much trend. But what do you think is more relevant to determining trend over the coming decades - the most recent 5 1/2 decades, or data from the 1800s?

Makes sense. It's not well sited, so it probably has a seasonal bias. MADIS does not have a good way to describe a cool bias, because typically the bias is warm. Funny too, his average error is higher over the past 28 days, even though only the Coatesville site is flagged due to the high standard deviation.

More misleading nonsense. Regarding the Tokyo data, you know something’s up when there’s a graph from Tony Heller’s wife limited to 1994-2021. You can pull up the raw data for Tokyo from JMA. There is, in fact, an inhomogeneity flagged in December 2014, consistent with the inflection point in this small subset of data. So the bias correction appears to be correct. Moreover, the long-term trend is actually greatly reduced by the UHI correction. That’s why nothing before 1994 is shown there. Further, the two warmest years in the raw data are the last two years (even without correcting for the change that occurred in 2014). 2025 appears well on its way to approaching those highs. Feel free to look for yourself: https://www.data.jma.go.jp/stats/data/en/index.html

While there hasn’t been any temps of 95 or higher, every day since June 21 has been above normal, with only 2 days below normal since June 4. That trend looks to continue for at least the next couple of weeks.

Looks like it rebounded to a daily high of 93. Probably just a result of variable cloud cover.

Funnily enough, the USCRN data largely supports my contention decades ago that the US climate record likely understates the change. If you accept USCRN as the gold standard, then, you must conclude nClimDiv [and the older USHCN] clearly understates warming in recent decades.

I do want to clarify one thing. I indicated USCRN has a slightly larger warming trend than nClimDiv over the period. I think that actually understates the difference. While the trend difference over the 21 years of overlap are relatively small, the magnitude of the trend is quite larger in USCRN. You can see Zeke Hausfather addressed this in 2023, after some images purporting to show minimal change in USCRN were shared on Twitter/X and picked up some steam. In reality, there was a large trend in the data masked by the much greater month-to-month variability in the data. The most accurate record of US temperatures shows rapid warming At that time, per Hausfather, the trends were 0.3C/decade for USCRN and 0.23C/decade for nClimDiv. Revisiting this with data updated through the first half of 2025, the difference has become a bit more substantial. Obviously, 2025 is incomplete, so these trends could be off a bit if the final annual anomaly deviates significantly. But I calculate the trend in USCRN at 0.47F/decade, or 4.7F/century, while nClimDiv is 0.34F/decade, or 3.4F/century. Note, I use degrees Fahrenheit, as opposed to degrees Celsius as Zeke did.

For comparison, July 2020. Simple arithmetic mean of 99 stations: 77.1F. NCEI reports 76.9F, or 0.2F cooler. If they are conducting some sort of massive increase in recent temperatures, they seem to be omitting the Midwest from the warming. To be honest, the earlier sample has a much greater proportion of center city and rooftop sites, with all of the city observations moved out to suburban airports and the city WSOs closed. So it's actually kind of surprising, there's no deviation from the simple mean, because there are clearly non-climatic biases in the data.

Here is the average of all available data in Ohio for July 1895: The reported value for that month is 71.1F, just 0.1F different than a simple average of the data. This is not the case for states with more significant elevation changes. Generally, the early data is devoid or limited of high elevation stations, so the simple average is often much higher than the gridded average. But most of the data for the Midwest matches pretty close to the reported data - like I said there are some adjustments made to later decades, but these are reasonable (change in TOBs and instruments). Ideally, we would have just maintained the 5 pm / 6 pm observations and CRS readings, and then there would be no need for any adjustments. But unfortunately, we don't live in the universe where those changes weren't made. I think it is reasonable to consider whether maybe to reinstate them at certain or all sites?

Meh, most of what's called adjustments is actually just areal averaging/gridding of the data. With states like Ohio or Illinois, where there aren't huge variations in elevation, and the stations have been pretty well separated throughout history, there's little discrepancy in the pre-1920 data versus what NCEI reports. There's a small decrease to account for observation time, and adjustment for instrument bias, from about the 1920s gradually decreasing in the 1960s to 1970s. Recent decades are generally slightly less. Why - I'm not sure, I guess a small negative UHI adjustment. Obviously, looking at individual sites, there can be significantly larger inhomogeneities - especially with some of them that have been shuttered and/or threaded with a bunch of disparate locations, elevations and site exposures.

There was no Cincinnati WSO until nearly 2000 - much of that appears to be made up "ghosted" data as you have referred to it in the past. For the period where there actually is data [i.e., up until the 1960s & 1970s], the adjusted & homogenized final product appears to decrease the trend. Moreover, this is a rooftop urban station. In recent years, temperatures at the airport - several hundred feet higher in elevation, with an aspirated temperature sensor, sited over grass - have exceeded even those lofty early years. Here's what the site looked like in 1947 (see illustration below). I would 100% favor bringing back these stations today and actually reporting the observed temperatures. Guarantee they would be far warmer than whatever is shown on there.

It looks like they did adjust the trend down. Rather than chill recent years, early years appear to be adjusted upwards, no? Pretty substantially in the 1960s and 70s, in fact. What am I missing here? The unadjusted data pretty clearly shows a steeper warming trend than the adjusted data.

Lol. There was no "Greater Pittsburgh Air Force Base" with data back to 1880. What a clown. This appears to be a mix & match of different stations threaded together. In fact, it looks to be the official station thread. Funny it cuts off in 2020. Even the airport [400+ feet higher in elevation] beat any year in history by 1F just last year.

As an aside, I find it hilariously hypocritical that @ChescoWx's signature complains about the use of the word "denier." He bandies that term around more than anyone here... calling people natural climate change deniers and cyclical climate change deniers.

Looks like there's a cooler Avondale site in the mix as well. It's also misleading to call Spring City site unusually warm. It looks to be the coolest NOAA site since 2000, at least in the month of July based on my analysis. Despite its closeness to Phoenixville, it is substantially cooler than Phoenixville. Indeed, it is even cooler than Avondale, which was cooler by 1+ degree during the overlap with the old Coatesville and West Chester sites. Like I said, it looks like the current station mix is the coldest since 2000, so you would think recent years would be adjusted upwards from the calculated average observed July mean, but it is actually a little lower than the mean of Avondale, Phoenixville, and Spring City [at least based on what you presented as NCEI's figure for the 2020s]. Remember when you add a huge slew of new stations that aren't included in the NOAA analysis, that's essentially the same as saying those locations were equal to the county mean for all prior years in which those sites did not exist. If those stations are instead below the mean of the existing NOAA sites, then that is not a valid form of averaging.

Interesting. @donsutherland1, do you find any evidence of a cyclical warming in the Phoenix data? Were the 1930s even hotter there, as seems to be insinuated here?

Don, I would also question the replicability of Shewchuk's graph, especially in recent years. I see no evidence of recent years being adjusted upwards, so that weird pause since 1998 makes zero sense. There have been plenty of recent years that have far exceeded 1998 (2012, 2023, 2024, etc.). It is worth pointing out that the redundant, higher quality CRN network was established in 2005 and shows slightly more warming than nClimDiv during the period of overlap. There is no evidence to suggest that recent data is being adjusted upwards. Looking at the rest of the graph, the magnitude of adjustments for TOBs and instrument changes looks to be of a reasonable magnitude. I know sometimes these graphics are manipulated by not factoring in gridding / proper areal averaging, which isn't an adjustment within the meaning of that term. Another common misrepresentation is to show only maximum temperature data. The MMTS bias adjustment is to lower older daytime maxima; however, the bias adjustment raises older minima. The net affect of these offsetting adjustments is negligable to Tavg trend. Here, it looks like Shewchuk uses Tavg, so I will say it doesn't appear to be as misleading as some of the stuff I have seen Heller and Martz publish. He does cutoff the analysis at 1925, because prior to that date [back to 1895], adjustments are minimal and I think it would ruin the presentation he wants to give that the warming results only from adjustments. Also, as I said previously, the recent data definitely looks off. Doesn't seem to jive with actual observations. Without that weird sudden dropoff post-1998 in the so-called "raw" data, the trends since 1960 would be quite similar in both the so-called "raw" and "altered" data.

Taking a look at the actual data, I was largely able to replicate NOAA's rankings/values from the raw data back to at least 2000. I limited this to 25 years, because it would be a big undertaking to expand significantly beyond that and you run into more data discontinuities as you head back in time. In the "Occasional Thoughts on CC" thread, user @ChescoWx claims an actual summertime mean of 72.8F for the 2000s, 73.2F for the 2010s, and 73.5F for the 2020s, which it is claimed that NOAA alters to 73.1F, 73.9F, and 74.1F. Limiting the analysis to actual NOAA stations, I calculate a summertime mean of 73.1F, 73.9F, and 74.4F for the three decades, the first two exactly matching the reported and the current decade actually slightly warmer than reported. It appears those values are calculated only by adding in stations that aren't included in the NOAA analysis - mesonets, secondary airports (AWOS sites?), perhaps personal weather stations. I'm not sure what's going on. In my analysis, I have data for Phoenixville 1E for 2000-2024, West Chester 2 NW for 2000-2016, Coatesville 2 W for 2000-2007, Avondale 2 N for 2006-2024, and Spring City 2 WSW for 2023-2024. Looking at this basket of stations, Phoenixville 1 E looks to be the warmest, followed by West Chester 2 NW, then Coatesville 2 W, then Avondale 2 N, and Spring City 2 WSW. So it looks like the station mix has gotten cooler with time with the Coatesville and West Chester sites gradually swapped out for the cooler Avondale and Spring City sites, so I would expect homogenization to increase the recent temperatures and/or decrease the older temperatures, but the opposite is true, with the older temperatures equal to the true mean and recent temperatures slightly chilled from the true mean. If anything, it looks like the NOAA trend for Chester County is slightly low for the most recent 25 summers?