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

[ChescoWx]

"That is a clear sign of a major station change, probably at Morgantown." That would be incorrect Charlie no station changes took place at all during the period that temperatures were reported by the NWS Coop observer. There were some moves after those temperature obs ended and they moved to just precip and snow obs. 

 

[chubbs]

20 hours ago, ChescoWx said:

"That is a clear sign of a major station change, probably at Morgantown." That would be incorrect Charlie no station changes took place at all during the period that temperatures were reported by the NWS Coop observer. There were some moves after those temperature obs ended and they moved to just precip and snow obs. 

 

Raw data determines whether there was a station change not NCDC documentation, which can be incomplete. The 2F cooling of Morgantown relative to Coatesville is clearly a station change of some kind. The Morgantown site was didn't operate for 5 months in the summer of 1966, station changes in Chester County that I have investigated usually coincided with station shutdowns.

[ChescoWx]

As per the World Meteorological Organization (WMO) Current climate normals are calculated using the past 3 complete decades and recalculated every 10 years. So, I went back and calculated what was normal for the last 10 climate normal periods specifically for Chester County PA. The below show what the climate normals were for the 10 years following each calculation with the earliest being 1901-1930 normals and the latest being our current climate normal period of 1991-2020. Averages in red are the warmest and blue the coolest across those periods. Of note our warmest climate normal period was 1931-1960 and our coolest period was 1961-1990.

[ChescoWx]

I split our weather database almost down the middle to compare how our climate here in Chester County has changed compared to the first 66 years of climate data (1893-1959) vs. the last 67 years of data (1960-2025).  Of note 7 months have trended cooler - 3 have trended warmer and 2 have remained about the same. Overall, on an annual basis we have trended cooler by 0.2 degrees during the latest period of record.

[ChescoWx]

Well if AI says it's so.....

[ChescoWx]

Due to multiple requests below for comparison I have added the recast National Centers for Environmental Information (NCEI) temperature data that includes the chilling adjustments to the older data. That chart is now below the actual raw data. I split our weather database almost down the middle to compare how our climate here in Chester County has changed compared to the first 66 years of climate data (1893-1959) vs. the last 67 years of data (1960-2025). With the actual data we see that 7 of our months have trended cooler - 3 have trended warmer and 2 have remained about the same. Overall, on an annual basis the actual raw data has trended cooler by 0.2 degrees during our most recent half of climate data 1960-2025. However, once NCEI applies their adjustments it paints a very different picture. We see clear warming in each and every month during our more recent climate history from 1960-2025. This aligns well with the expected warming narrative.

[Stormchaserchuck1]

You can't tell by personal observations, of say snow, that things are progressing in a direction? 

[ChescoWx]

59 minutes ago, Stormchaserchuck1 said:

You can't tell by personal observations, of say snow, that things are progressing in a direction? 

Truth! Only long running climate data works!