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

[ChescoWx]

So let's go ahead and use the adjusted NCEI average annual temperatures for Chester County PA from NCEI this century. These are the adjusted altered figures Charlie....what does this tell us?  Even after adjustments by NOAA PHL is indeed warming almost 70% faster than Chester County PA - the PHL UHI is a problem even NOAA shows it....

[chubbs]

20 hours ago, ChescoWx said:

Bad assumption only using the warmest station which is Phoenixville 1E - to better determine the true Chesco average you should add in the nice mix we have today of high and low elevations to capture the true average Chester County average temperature. Heck the averages I derive from these stations is in reality supports almost exactly the calculated average temperatures posted by NCEI on their site for their recent Chester County PA average temperatures. If NCEI develops an average temperature for the county that is statistically the same as what I calculate from the raw stations. See below since 2004. NCEI must think the mix of stations I use is strong correct? 

I have no problem with your current set of stations. As you say it provides good coverage and matches NCEI. The problem isn't the current stations, its the difference between the current stations and the older stations. There isn't a single current station in the county that is as warm as any of the 3 county stations in 1945. You can't get our climate history right without properly accounting for the changes in county stations with time. Note also that consistency is much more important than coverage when tracking long term changes in temperature. 

[chubbs]

On 5/22/2026 at 12:42 PM, ChescoWx said:

So let's go ahead and use the adjusted NCEI average annual temperatures for Chester County PA from NCEI this century. These are the adjusted altered figures Charlie....what does this tell us?  Even after adjustments by NOAA PHL is indeed warming almost 70% faster than Chester County PA - the PHL UHI is a problem even NOAA shows it....

The difference in slope is not statistically significant. That said, wouldn't be surprised if PHL had a some warming enhancement from UHI; but, based on comparisons to other sites it is small compared to the region-wide warming in recent decades. More data is needed to make the case though. Note that the Avondale USHCRN station has a higher slope than PHL. Are you saying that the warming there is due to UHI?

[ChescoWx]

No matter how you slice it using either the raw or altered adjusted data. The gap is clearly widening between PHL and Chester County

[chubbs]

17 hours ago, ChescoWx said:

No matter how you slice it using either the raw or altered adjusted data. The gap is clearly widening between PHL and Chester County

But it does matter how you slice it; and, you continue to cherry pick favorable comparisons and ignore the rest. I stated above that the slope difference between NCEI and PHL between 2000 and 2025 was not statistically different. Expanding the yaxis doesn't change that result.

Looking over a longer period and re-normalizing the yaxis, we see that the delta between Chester County and the Philadelphia Airport has stayed the same since 1970. The delta goes up and down but without a long-term trend; 2000 just happens to be a minimum. Doesn't matter whether you use NCEI or high quality sites like Coatesville, Avondale USCRN, and DEOS. The answer is the same.