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

[TheClimateChanger]

On 6/8/2025 at 6:35 AM, chubbs said:

Your in denial mode. These two charts fit together well. The station moves at Coatesville and West Chester produce spurious cooling if they are left in the raw data. That's why NOAA matches raw data without station moves and you (COOP station avg) don't. You have Chester County as warm as the Philadelphia airport before the station moves. How silly is that.

@chubbs - this is all a bunch of subterfuge. In the vast majority of cases, NOAA systematically reduces the reported temperatures from the observed temperatures on a county-by-county basis, often in ways that make little logical sense. Chester County may very well be the only county in Pennsylvania where the opposite is true. So if there is a conspiracy, it's in the opposite direction as the one presupposed with this analysis.

 

 

 

[TheClimateChanger]

Let's look at May 2025:

xMacis reveals three NOAA stations in Chester County, with a mean temperature of 61.5F. So it's true that the reported mean temperature is higher than the mean of these three stations. But the opposite is true in just about every other county in Pennsylvania.

[bdgwx]

And at the global level the net effect of all adjustments actually reduces the overall warming trend.

[Haufather 2017]

[chubbs]

21 hours ago, TheClimateChanger said:

@chubbs - this is all a bunch of subterfuge. In the vast majority of cases, NOAA systematically reduces the reported temperatures from the observed temperatures on a county-by-county basis, often in ways that make little logical sense. Chester County may very well be the only county in Pennsylvania where the opposite is true. So if there is a conspiracy, it's in the opposite direction as the one presupposed with this analysis.

 

 

 

The Chester County deep-dive has shown that a county station average is a terrible way to evaluate NOAA. The available stations aren't designed to produce county averages by simple averaging and the stations change with time. The average shelf life of a coop station isn't very long. Even stations with long-term records have station moves and equipment changes.

The NOAA method is well proven for getting the right answer from a constantly changing station network. If the stations didn't change then simpler methods would also work; but, as we have seen in Chester County the simpler methods breakdown when there are large changes in the station network with time.

 

[TheClimateChanger]

On 6/28/2025 at 5:48 AM, chubbs said:

The Chester County deep-dive has shown that a county station average is a terrible way to evaluate NOAA. The available stations aren't designed to produce county averages by simple averaging and the stations change with time. The average shelf life of a coop station isn't very long. Even stations with long-term records have station moves and equipment changes.

The NOAA method is well proven for getting the right answer from a constantly changing station network. If the stations didn't change then simpler methods would also work; but, as we have seen in Chester County the simpler methods breakdown when there are large changes in the station network with time.

 

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?

[ChescoWx]

10 minutes ago, TheClimateChanger said:

 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.

 

Below are the stations used and dates operational

[ChescoWx]

The Phoenixville and Spring City sites that are now the only remaining NWS COOP stations of course run warmer than all other stations in 24 of the last 25 years. On average a 0.8 degree variation. With those sites running as much as 3 degrees too warm in one year and at least a degree warmer in 15 of those years!! Makes very little sense as these 2 stations are much lower in elevation and near each other in the Northeastern section of Chester County....yet these are the 2 stations that NCEI will use to calculate their county averages.....call me stunned!! LOL! 

[ChescoWx]

Look at how close these 2 stations are in NE Chesco....certainly not representative of the county climate

[ChescoWx]

On 6/28/2025 at 5:48 AM, chubbs said:

The Chester County deep-dive has shown that a county station average is a terrible way to evaluate NOAA. The available stations aren't designed to produce county averages by simple averaging and the stations change with time. The average shelf life of a coop station isn't very long. Even stations with long-term records have station moves and equipment changes.

The NOAA method is well proven for getting the right answer from a constantly changing station network. If the stations didn't change then simpler methods would also work; but, as we have seen in Chester County the simpler methods breakdown when there are large changes in the station network with time.

 

fixed it for you - The NOAA method is well proven for getting the DESIRED answer

[TheClimateChanger]

2 hours ago, ChescoWx said:

Look at how close these 2 stations are in NE Chesco....certainly not representative of the county climate

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.

[ChescoWx]

So I have finally completed the analysis of the Ghost Data stations and compared their inputs vs. the actual averages across the County. NOAA has employed techniques like interpolation to estimate temperatures in what they normally would say are data-sparse regions and in other cases this data may be resampled from another grid.  Of note there are seven (7) ghost stations employed across Chester County PA with this estimated temperature data in the period of record from 1895 through 2013. All of these were during the ghost years reporting only precipitation data. Some eventually did begin actual temperature reporting after the ghost years. The Ghost Stations and years of estimated data are Phoenixville (1895-1914) / West Grove (1928-1962) / Coatesville (1948-1955) / Glenmoore (1957-2005) / Honey Brook (1957-2013) / West Chester 2W (1979-1981) and Devault (1988-2004). Overall there are 189 years of ghosted data used to "fill in data gaps". Of note this ghost data was warmer than the actual county records in 101 of the 106 years of ghosted data between 1895 and the "shuttering "of the last remaining ghost station at Honey Brook in 2013.. The largest warming adjustments were unsurprisingly made during the coldest decades of the 1960's and 1970's. Below is an analysis of the impact on average temperature trend lines between the actual raw data and ghost data in the years these adjustments were applied. Some more analysis on this data will follow. 

[chubbs]

1 hour ago, ChescoWx said:

So I have finally completed the analysis of the Ghost Data stations and compared their inputs vs. the actual averages across the County. NOAA has employed techniques like interpolation to estimate temperatures in what they normally would say are data-sparse regions and in other cases this data may be resampled from another grid.  Of note there are seven (7) ghost stations employed across Chester County PA with this estimated temperature data in the period of record from 1895 through 2013. All of these were during the ghost years reporting only precipitation data. Some eventually did begin actual temperature reporting after the ghost years. The Ghost Stations and years of estimated data are Phoenixville (1895-1914) / West Grove (1928-1962) / Coatesville (1948-1955) / Glenmoore (1957-2005) / Honey Brook (1957-2013) / West Chester 2W (1979-1981) and Devault (1988-2004). Overall there are 189 years of ghosted data used to "fill in data gaps". Of note this ghost data was warmer than the actual county records in 101 of the 106 years of ghosted data between 1895 and the "shuttering "of the last remaining ghost station at Honey Brook in 2013.. The largest warming adjustments were unsurprisingly made during the coldest decades of the 1960's and 1970's. Below is an analysis of the impact on average temperature trend lines between the actual raw data and ghost data in the years these adjustments were applied. Some more analysis on this data will follow. 

Don't know what you are talking about. Can you provide a link to the so called "ghost data".

[ChescoWx]

1 hour ago, chubbs said:

Don't know what you are talking about. Can you provide a link to the so called "ghost data".

https://mesonet.agron.iastate.edu/request/coop/fe.phtml?network=PACLIMATE

One example of many below....this is a precipitation only station - so those Tmax and Tmins are ghosted estimated data......

[ChescoWx]

Looks like another temperature Ghost Station with the Coatesville 1E precipitation only station....generating high and low daily temps without the observer doing so! Thought ghost data ended back in 2014....looks like it continued right through the end of 2022....