Occasional Thoughts on Climate Change

[chubbs]

Here's 90F data from two of your 500"+ sites, from your Chescowx series. No wonder you are finding a decrease in 90F days. There are other factors besides elevation that impact 90F. Factors you aren't considering. You still haven't addressed or justified your N+W station shift.

The difference in 90F days between Coatesville 2W and ENantmeal is the kind of information you don't disclose when you release an analysis. You have been putting out misleading local climate info for decades. Good thing we have NOAA for groundtruth.

[chubbs]

2 hours ago, ChescoWx said:

No bias in basket of stations they are all available NOAA / AWOS and MADIS sites at our disposal

You can't say that because, unlike NOAA,  you haven't checked for bias. As shown above there are big differences in 90F days from station to station. So its critical not to allow station selection or measurement bias to impact the results. You are making rookie mistakes by just averaging the station data without any attempts to remove bias. To detect climate change you need to remove measurement inconsistency; but instead, you are adding inconsistency be shifting station locations. Instead of criticizing NOAA you should be learning how to improve your results.

As I said above you are beating a dead horse. One flawed analysis after the other. All very similar, No new information.  Meanwhile, as the data from your own house shows, our local climate steadily warms. As I have said many times in the past. You are going to be the last guy to realize Chesco is warming.

[TheClimateChanger]

3 hours ago, chubbs said:

Here's 90F data from two of your 500"+ sites, from your Chescowx series. No wonder you are finding a decrease in 90F days. There are other factors besides elevation that impact 90F. Factors you aren't considering. You still haven't addressed or justified your N+W station shift.

The difference in 90F days between Coatesville 2W and ENantmeal is the kind of information you don't disclose when you release an analysis. You have been putting out misleading local climate info for decades. Good thing we have NOAA for groundtruth.

Got to love that period of overlap. The site with more than twice as many 90+ days drops out after a handful of years of overlap, and replaced with his own weather station. Oh, lookey here, 90+ days are plummeting! At the same time everyone else is sweltering through three scorching summers (2010-2012). 

Honestly, I'm not even sure if the trend from his own backyard data is "real" because he has changed equipment and siting in that time. I bet there was a change around 2012/2013. For all the hullabaloo about siting, his "official" station [he has three] is right next to a stand of tall trees. Clearly not sited at a distance 4x the length of the obstructions, with considerable shading. Unironically, the rooftop station is probably the best sited in his case.

[ChescoWx]

So I have updated the average number of 90 degree days to include the Philadelphia International Airport and overlaid that analysis over the Chester County data shared yesterday. You can clearly see the impact of the urban heat island (UHI) on the official Philadelphia climate site (the red line is the rapid heat growth). While 90 degrees are declining in Chester County they are rapidly increasing in frequency at the airport. So far in the 2020's PHL is averaging more than 3 weeks of additional 90+ days than here in Chester County.

In 1940 when weather observations started at the airport it's footprint was only around 300 acres. Since 1940 the PHL Airport has expanded to over 2,600 acres. That is a staggering 2,078% growth. The significant impact to the official Philadelphia climate data due to this rapid expansion is clearly illustrated below.

Especially starting in 1970 when we began to see huge increases in the addition of asphalt, concrete and taxi ways. In 1970 alone the airport added 64% more gates and buildings. Just 2 years later in 1972 runways were expanded to handle 747's. Then 4 new terminals were added in 1977 and parking spaces were increased from 5k to 20k. Rapid increase in asphalt continued in 2002 with an additional 8 miles of pavement added to the site. In 2005 runways were increased and as of today there is now 33,000 feet of asphalt runway at the airport. Next time you see the reporting of 90 degree days on TV.....keep in mind where those figures are coming from - it is not where people live.

[ChescoWx]

9 minutes ago, TheClimateChanger said:

Got to love that period of overlap. The site with more than twice as many 90+ days drops out after a handful of years of overlap, and replaced with his own weather station. Oh, lookey here, 90+ days are plummeting! At the same time everyone else is sweltering through three scorching summers (2010-2012). 

Honestly, I'm not even sure if the trend from his own backyard data is "real" because he has changed equipment and siting in that time. I bet there was a change around 2012/2013. For all the hullabaloo about siting, his "official" station [he has three] is right next to a stand of tall trees. Clearly not sited at a distance 4x the length of the obstructions, with considerable shading. Unironically, the rooftop station is probably the best sited in his case.

Nope! nothing dropped out all sites are included for instance if everyone else was "sweltering" how did we only see 2010 (12) / 2011 (15) / 2012 (11) such days at KMQS and only 8 such days at Atglen in 2012 - that sure ain't sweltering in my book!!

[ChescoWx]

34 minutes ago, TheClimateChanger said:

Got to love that period of overlap. The site with more than twice as many 90+ days drops out after a handful of years of overlap, and replaced with his own weather station. Oh, lookey here, 90+ days are plummeting! At the same time everyone else is sweltering through three scorching summers (2010-2012). 

Honestly, I'm not even sure if the trend from his own backyard data is "real" because he has changed equipment and siting in that time. I bet there was a change around 2012/2013. For all the hullabaloo about siting, his "official" station [he has three] is right next to a stand of tall trees. Clearly not sited at a distance 4x the length of the obstructions, with considerable shading. Unironically, the rooftop station is probably the best sited in his case.

My data is of course a small minority piece of the data and I am not even the coolest station in the reporting set. My station is appropriately sited according to site and exposure standards with the station location that is in fact "typical of the surrounding area". The standards go on to say that "when possible" (it is not in my township) four times the height of any obstruction (tree, fence, building, etc.). The sensor should be at least 100 feet from any paved or concrete surface. it is. My data has also been validated by the Gladstone quality check for weather data.

[ChescoWx]

Ruh roh! More problems for the climate doomers!!  A new Monmouth University poll reveals that the percentage of Americans ages 18-34 who view [man induced] climate change as a very serious problem has fallen by 17 % points in just the last 3-years, from 67% in 2021 to 50% this year. Concern among folks aged 34-54 declined from 48% to 44%, and ages 55+ down to 44% from 54% over the same period. Support for government action to reduce greenhouse gas (GHG) emissions in the 18-34 age demographic fell from 82% in 2018 and 80% in 2021 to 62% in the latest poll, a whopping 18-20 percentage point drop. For the ages 35-54 group, it stands at 55% down from 62% in 2021 and 66% in 2018. Good to see the non-homogenized raw actual data starting to change minds!! Climate change is real and constant no one can deny this....but folks are indeed catching on that there is not a climate crisis and of course nothing at all to be alarmed at!

[rcostell]

"Good to see the non-homogenized raw actual data starting to change minds!! Climate change is real and constant no one can deny this....but folks are indeed catching on that there is not a climate crisis and of course nothing at all to be alarmed at!" - Completely fabricated singular opinion.   Stop the back spin "propoganda" and look at other data.     See below link as example.  Climate change may be "constant"- but its clear the rate of warming is unprecedented in recent geologic time.   Too many correlations and data to keep spinning this in a way that insults common sense.  Please stop. 

 

https://www.noaa.gov/news-release/noaa-confirms-4th-global-coral-bleaching-event

[LibertyBell]

On 5/6/2024 at 1:45 PM, TheClimateChanger said:

No, I don't believe the government. They have consistently downplayed this for decades. The data shows it has warmed much more than the government statistics claim.

Yes this is why action has been delayed.

It's very similar to what happened with PFOA and the sugar cartels too.

 

[LibertyBell]

15 hours ago, TheClimateChanger said:

Well you know I'm going to have to comment.

(1) Data from 1920s - 1960s is likely not directly comparable to more recent data at some of the sites. May co-op stations reset their thermometers at 5 or 6 pm, and thus would register extra 90s on hot days [when the following day may or may not have reached 90]. Would expect this to add at least a couple or few extra 90-degree days on average each year.

(2) The trend is minimal from the low elevation sites, and biased due to weighting 2020s equally even though only 4 years are included. It looks like the 2020s have had an unusually low number of 90+ days, but it's based on only 4 years of data. Same thing with the high elevation sites, but you also then extrapolate the trend back to the 1890s even though the data stops in the 1950s. In fact, the trends from 1950s to the present are about the same and we can be pretty confident that general pattern would have persisted into the 1890s. So the big drop off implied in the regression is clearly not accurate. If the remainder of the 2020s have a high number of 90+ readings, the trends could be significantly different. 

(3) These trends do not agree with Philadelphia data [from a county neighboring Chester County]. These data were collected by trained meteorologists from the Weather Bureau and later National Weather Service, and thus are less likely to contain errors and are unaffected by any changes in observation time. I can anticipate you will claim the UHI effect is the culprit, but there's no explanation for why center city Philadelphia would have fewer 90-degree days than Chester County, which would have been very rural, in the 19th century and early 20th century.

 

There is a reason why this is happening-- it's raining much more now than it did back then.  The extreme amount of rainfall and high soil moisture is the reason why high temperatures are being blunted-- I hate it! I love high heat and low rainfall and low humidity.

 

[LibertyBell]

14 hours ago, TheClimateChanger said:

Also, low temperatures in the 1930s and 1940s were much colder than today. You don't need air conditioning when it cools off into the 50s at night. You open the windows.

Coldest mean summertime lows

Morgantown, WV

Wheeling, WV

Warmest mean summertime lows

Morgantown, WV [some of this 19th century data is suspect, but you get the picture]

Wheeling, WV

it's because of lower humidity and much drier air back then

I loved that climate, I hate high rainfall and lower high temps.

 

[chubbs]

6 hours ago, ChescoWx said:

So I have updated the average number of 90 degree days to include the Philadelphia International Airport and overlaid that analysis over the Chester County data shared yesterday. You can clearly see the impact of the urban heat island (UHI) on the official Philadelphia climate site (the red line is the rapid heat growth). While 90 degrees are declining in Chester County they are rapidly increasing in frequency at the airport. So far in the 2020's PHL is averaging more than 3 weeks of additional 90+ days than here in Chester County.

In 1940 when weather observations started at the airport it's footprint was only around 300 acres. Since 1940 the PHL Airport has expanded to over 2,600 acres. That is a staggering 2,078% growth. The significant impact to the official Philadelphia climate data due to this rapid expansion is clearly illustrated below.

Especially starting in 1970 when we began to see huge increases in the addition of asphalt, concrete and taxi ways. In 1970 alone the airport added 64% more gates and buildings. Just 2 years later in 1972 runways were expanded to handle 747's. Then 4 new terminals were added in 1977 and parking spaces were increased from 5k to 20k. Rapid increase in asphalt continued in 2002 with an additional 8 miles of pavement added to the site. In 2005 runways were increased and as of today there is now 33,000 feet of asphalt runway at the airport. Next time you see the reporting of 90 degree days on TV.....keep in mind where those figures are coming from - it is not where people live.

You aren't providing any evidence on heat island impacts at PHL. PHL 90F days tracks other I95 airports in our area closely. ILG (Wilmington) and VAY (Mt Holly) are much smaller airports that aren't changing very quickly.  Meanwhile your data is filled with inconsistency with station locations varying with time moving north and west. To say nothing of subbing in your own house which hardly ever gets a 90F day. 

Heat island mainly impact nighttime temps. Effects on daytime highs are much smaller. My own station tracks closer to PHL than your house, both for summer high temperatures and number of 90F days. In the past 3 years phl has averaged 36 90F days and I've averaged 20.  PHL gets about the same number of days above 92. Considering I'm at almost 300' with a heavily shaded back yard bordering on woods, That doesn't leave much room for a big heat island effect on PHL 90F days. In terms of climate trends for our area I'll take phl, a single site with a long-term record, over your biased county average any day. 

[ChescoWx]

2 hours ago, chubbs said:

You aren't providing any evidence on heat island impacts at PHL. PHL 90F days tracks other I95 airports in our area closely. ILG (Wilmington) and VAY (Mt Holly) are much smaller airports that aren't changing very quickly.  Meanwhile your data is filled with inconsistency with station locations varying with time moving north and west. To say nothing of subbing in your own house which hardly ever gets a 90F day. 

Heat island mainly impact nighttime temps. Effects on daytime highs are much smaller. My own station tracks closer to PHL than your house, both for summer high temperatures and number of 90F days. In the past 3 years phl has averaged 36 90F days and I've averaged 20.  PHL gets about the same number of days above 92. Considering I'm at almost 300' with a heavily shaded back yard bordering on woods, That doesn't leave much room for a big heat island effect on PHL 90F days. In terms of climate trends for our area I'll take phl, a single site with a long-term record, over your biased county average any day. 

Do better Charlie! No data has been "subbed out" all data is included and split between individual observation sites. I have even broken it down by elevation to address any relative elevation biases. And of course my spotter data is a minute part and not event the coldest historical locale in Chester County PA data set of 27 stations.

[csnavywx]

Ya'll are wasting your time. He's already admitted he doesn't have any conditions under which he would change his mind -- so anything you use will simply reinforce the dissonance.

[chubbs]

8 hours ago, csnavywx said:

Ya'll are wasting your time. He's already admitted he doesn't have any conditions under which he would change his mind -- so anything you use will simply reinforce the dissonance.

Don't disagree. Am posting mainly because the local data and how it is tortured is of interest. This week I've learned that most of our coop sites that cover multiple recent decades have an upward trend in 90F days.

[chubbs]

11 hours ago, ChescoWx said:

Do better Charlie! No data has been "subbed out" all data is included and split between individual observation sites. I have even broken it down by elevation to address any relative elevation biases. And of course my spotter data is a minute part and not event the coldest historical locale in Chester County PA data set of 27 stations.

You misinterpreted or didn't understand what I said. Let me try again because it is an important point. With the same weather conditions East Nantmeal will measure fewer 90F days than Coatesville 2W. We know that by comparing years when both stations operate. If the station population is changed by replacing Coatesville 2W when it shuts down with East Nantmeal when you moved there, then the 90F days will be reduced due to the difference in 90F days measured at the two stations. You aren't determining the County climate trend. Instead you are producing a station population trend, Your station population is trending cooler and with less 90F days with time.

Below is what I have gathered so far on the elevated sites. I only had time to get the last 2 years at Atglen and Glenmooredeos. Clearly the changing station population is driving the results, not the climate. The older stations with longer records: GlenmooreCoop, Honey Brook and Coatesville,all have a similar and increasing level of 90F days over multiple decades. The newer stations with shorter records: KMQS (Coatesville Airport), East Nantmeal, Atglen and GlenmooreDeos are also similar. All have intrinsically fewer 90F days than the three older stations. Clearly seen by comparing the years when older and newer stations are operating.

There is a big change in station population in going from Glenmoorecoop, Honey Brook and Coatesville2W alone in the 50s-90s. To a station mix which is primarily made up of stations with relatively low 90F days from 2004 onwards. Now that GlenmooreCoop, the last of the older station, has shut down, 90F days are going to trend down going forward no matter how much Chester County warms. You will be trumpeting the results I am sure.

Finally your house is not exactly a minute part of the elevated stations and is clearly pulling down the elevated 90F average since 2004. The more I see of your new method the worse it looks. More biased than Chescowx for sure. Shows how good a bias metric NOAA is. The further away you are from NOAA the more bias you are introducing.

 

[bluewave]

PHL has had a similar amount of 90° days since 2010 as more rural to suburban COOP sites in NJ. 
 

Monthly Number of Days Max Temperature >= 90 for PHILADELPHIA INTL AP, PA
Click column heading to sort ascending, click again to sort descending.

Year	Apr	May	Jun	Jul	Aug	Sep	Oct	Season
Mean	0	2	6	15	9	3	0	35
2023	0	0	1	13	3	7	0	24
2022	0	3	5	19	19	2	0	48
2021	0	3	9	10	15	0	0	37
2020	0	0	5	21	10	0	0	36
2019	0	1	4	18	8	3	1	35
2018	0	1	4	11	10	4	0	30
2017	0	3	6	11	4	2	0	26
2016	0	3	5	16	17	5	0	46
2015	0	1	7	10	12	7	0	37
2014	0	0	3	11	3	2	0	19
2013	0	3	4	12	0	1	0	20
2012	0	2	7	21	8	1	0	39
2011	0	3	5	21	4	0	0	33
2010	0	2	15	19	12	7	0	55

 

Monthly Number of Days Max Temperature >= 90 for HIGHTSTOWN 2 W, NJ
Click column heading to sort ascending, click again to sort descending.

Year	Apr	May	Jun	Jul	Aug	Sep	Oct	Season
Mean	0	2	6	15	9	3	0	35
2023	0	0	2	18	5	6	0	31
2022	0	3	3	22	19	2	0	49
2021	0	3	10	14	13	1	0	41
2020	0	0	5	23	13	1	0	42
2019	0	0	4	16	10	4	1	35
2018	0	3	4	12	13	4	0	36
2017	0	3	6	11	4	2	0	26
2016	0	4	4	17	16	5	0	46
2015	0	3	7	9	10	7	0	36
2014	0	0	7	12	2	6	0	27
2013	0	1	7	11	0	2	0	21
2012	1	2	6	16	5	1	0	31
2011	0	2	4	16	5	0	0	27
2010	1	3	10	17	11	6	0	48

 

Monthly Number of Days Max Temperature >= 90 for FREEHOLD-MARLBORO, NJ
Click column heading to sort ascending, click again to sort descending.

Year	Apr	May	Jun	Jul	Aug	Sep	Oct	Season
Mean	0	2	6	15	8	3	0	34
2023	0	0	1	13	0	4	0	18
2022	0	2	4	22	11	3	0	42
2021	0	3	14	13	12	1	0	43
2020	0	0	6	18	14	2	0	40
2019	0	0	4	16	8	4	1	33
2018	0	5	7	15	17	4	0	48
2017	0	3	5	10	4	2	0	24
2016	0	4	2	16	14	6	0	42
2015	0	0	4	10	13	7	0	34
2014	0	0	4	10	0	5	0	19
2013	0	1	7	12	0	2	0	22
2012	1	1	5	17	5	1	0	30
2011	0	0	3	16	5	0	0	24
2010	1	3	12	19	12	5	0	52

[Typhoon Tip]

Possible physical mechanism for the west Pacific warm pool and other consequences found

https://phys.org/news/2024-05-north-pacific-due-china-aerosols.html

This is important. For example, "break away" ridge nodes, containing climate anomalous warm atmospheric plumes, then meander down stream of these Rosby Wave sources and cause havoc. 

In a separate study cites the principle cause for the mega heat wave in the Pacific NW in June 2021 to be such a plume that migrated into a position over the Pac NW, stalled and then festered under solar maximum irradiance of that time of year.  

It also most likely means something for seasonal forecasting;  the ENSO correlations have been less stable/coherent to the winter time patterns, for example.  It's entirely intuitive that there is some negative interference, slow moving, at very large scaled mass fields ...etc.

 

[ChescoWx]

4 hours ago, chubbs said:

You misinterpreted or didn't understand what I said. Let me try again because it is an important point. With the same weather conditions East Nantmeal will measure fewer 90F days than Coatesville 2W. We know that by comparing years when both stations operate. If the station population is changed by replacing Coatesville 2W when it shuts down with East Nantmeal when you moved there, then the 90F days will be reduced due to the difference in 90F days measured at the two stations. You aren't determining the County climate trend. Instead you are producing a station population trend, Your station population is trending cooler and with less 90F days with time.

Below is what I have gathered so far on the elevated sites. I only had time to get the last 2 years at Atglen and Glenmooredeos. Clearly the changing station population is driving the results, not the climate. The older stations with longer records: GlenmooreCoop, Honey Brook and Coatesville,all have a similar and increasing level of 90F days over multiple decades. The newer stations with shorter records: KMQS (Coatesville Airport), East Nantmeal, Atglen and GlenmooreDeos are also similar. All have intrinsically fewer 90F days than the three older stations. Clearly seen by comparing the years when older and newer stations are operating.

There is a big change in station population in going from Glenmoorecoop, Honey Brook and Coatesville2W alone in the 50s-90s. To a station mix which is primarily made up of stations with relatively low 90F days from 2004 onwards. Now that GlenmooreCoop, the last of the older station, has shut down, 90F days are going to trend down going forward no matter how much Chester County warms. You will be trumpeting the results I am sure.

Finally your house is not exactly a minute part of the elevated stations and is clearly pulling down the elevated 90F average since 2004. The more I see of your new method the worse it looks. More biased than Chescowx for sure. Shows how good a bias metric NOAA is. The further away you are from NOAA the more bias you are introducing.

 

This is not difficult Charlie the bias in the overall Chesco data is as of the last couple years now actually biased to the warmer lower elevation locales not the higher! In 2023 there are 11 lower elevation spots vs 6 higher. This is why we now have split the data to account for such biases.

[TheClimateChanger]

4 hours ago, chubbs said:

You misinterpreted or didn't understand what I said. Let me try again because it is an important point. With the same weather conditions East Nantmeal will measure fewer 90F days than Coatesville 2W. We know that by comparing years when both stations operate. If the station population is changed by replacing Coatesville 2W when it shuts down with East Nantmeal when you moved there, then the 90F days will be reduced due to the difference in 90F days measured at the two stations. You aren't determining the County climate trend. Instead you are producing a station population trend, Your station population is trending cooler and with less 90F days with time.

Below is what I have gathered so far on the elevated sites. I only had time to get the last 2 years at Atglen and Glenmooredeos. Clearly the changing station population is driving the results, not the climate. The older stations with longer records: GlenmooreCoop, Honey Brook and Coatesville,all have a similar and increasing level of 90F days over multiple decades. The newer stations with shorter records: KMQS (Coatesville Airport), East Nantmeal, Atglen and GlenmooreDeos are also similar. All have intrinsically fewer 90F days than the three older stations. Clearly seen by comparing the years when older and newer stations are operating.

There is a big change in station population in going from Glenmoorecoop, Honey Brook and Coatesville2W alone in the 50s-90s. To a station mix which is primarily made up of stations with relatively low 90F days from 2004 onwards. Now that GlenmooreCoop, the last of the older station, has shut down, 90F days are going to trend down going forward no matter how much Chester County warms. You will be trumpeting the results I am sure.

Finally your house is not exactly a minute part of the elevated stations and is clearly pulling down the elevated 90F average since 2004. The more I see of your new method the worse it looks. More biased than Chescowx for sure. Shows how good a bias metric NOAA is. The further away you are from NOAA the more bias you are introducing.

 

This is what I suggested might be the case. Each of the individual component stations with a positive trend, while averaging across the basket of stations [changing over time] manufactures a negative trend. You did not put the Coatesville 2W trend, but it certainly looks positive over the period for which data is available. MQS is probably positive, although it could be flat or slightly down due to starting near a warm set of summers. Chesco's BY data is slightly down, but, like I said yesterday, that's probably just an artifact of him changing equipment.

[ChescoWx]

Because we actually do have the data let's review Charlie's statement that "the older stations with longer records: GlenmooreCoop, Honey Brook and Coatesville,all have a similar and increasing level of 90F days over multiple decades"

Well the actual data Charlie references is below (the yellow highlights are incomplete decades) However, in reality all of the mentioned stations they are the opposite of trending toward an increasing level of 90 degree days. In fact they have trended downward in 90+ days in the complete decades since the 1980's!! Again so different from the UHI problems at PHL. But overall absolutely no clear trend -simply cyclical changes by decade as we have always seen.

[ChescoWx]

1 hour ago, TheClimateChanger said:

This is what I suggested might be the case. Each of the individual component stations with a positive trend, while averaging across the basket of stations [changing over time] manufactures a negative trend. You did not put the Coatesville 2W trend, but it certainly looks positive over the period for which data is available. MQS is probably positive, although it could be flat or slightly down due to starting near a warm set of summers. Chesco's BY data is slightly down, but, like I said yesterday, that's probably just an artifact of him changing equipment.

Climate changer couple things. See above the Coatesville 2W trend is not positive over the period. Just to clarify I have used the same equipment for 21 years in East Nantmeal so no changes or variations there!! Does that help?

[TheClimateChanger]

1 hour ago, ChescoWx said:

Climate changer couple things. See above the Coatesville 2W trend is not positive over the period. Just to clarify I have used the same equipment for 21 years in East Nantmeal so no changes or variations there!! Does that help?

I just don't buy it. When I look at the annual weather review from 1950, Philadelphia was renowned for its moderate climate - seldom getting too cold or hot. They do acknowledge the humidity adds to the discomfort of the summertime temperature, but I'd be willing to bet humidity has gone way up since then.  As for as temperatures were concerned, they report an average of 14 90+ days, but this was from a hot rooftop site in the center city.  Today, Philadelphia is a blazing inferno in the summertime where you would die without A/C. Who even knows when the last time there was 14 or fewer 90+ days?

Rooftop stations can get way hotter during the day than ground-level stations. What really gets the noggin joggin' is this is how all the old temperatures were taken. So how cold was it really in the past? Like in 1999, NOAA said "SHUT IT DOWN"... yet that's how the temperatures had always been taken at the Baltimore Common House. Wouldn't that bias have been present throughout the history of the site, and then we just graft on the much colder airport records. And, of course, people still kvetch about those BWI temperatures all the time. 

Source: How not to measure temperature, part 48. NOAA cites errors with Baltimore's Rooftop USHCN Station – Watts Up With That?

[TheClimateChanger]

My question: if I installed a mercury thermometer housed in a Stevenson screen or cotton region shelter on a hot rooftop in center city Philly, how many 90+ days would it register each summer these days?

[ChescoWx]

10 minutes ago, TheClimateChanger said:

I just don't buy it. When I look at the annual weather review from 1950, Philadelphia was renowned for its moderate climate - seldom getting too cold or hot. They do acknowledge the humidity adds to the discomfort of the summertime temperature, but I'd be willing to bet humidity has gone way up since then.  As for as temperatures were concerned, they report an average of 14 90+ days, but this was from a hot rooftop site in the center city.  Today, Philadelphia is a blazing inferno in the summertime where you would die without A/C. Who even knows when the last time there was 14 or fewer 90+ days?

Rooftop stations can get way hotter during the day than ground-level stations. What really gets the noggin joggin' is this is how all the old temperatures were taken. So how cold was it really in the past? Like in 1999, NOAA said "SHUT IT DOWN"... yet that's how the temperatures had always been taken at the Baltimore Common House. Wouldn't that bias have been present throughout the history of the site, and then we just graft on the much colder airport records. And, of course, people still kvetch about those BWI temperatures all the time. 

Source: How not to measure temperature, part 48. NOAA cites errors with Baltimore's Rooftop USHCN Station – Watts Up With That?

The city was also way less built up and the UHI factor was not nearly so impactful as today. Regarding near the old normal of 14 days before UHI PHL has been close or below that figure in 2014 (19) / 2009 (15) / 2004 (9) / 2000 (10) / 1996 (7) and 1992 (14)

[TheClimateChanger]

4 minutes ago, ChescoWx said:

The city was also way less built up and the UHI factor was not nearly so impactful as today. Regarding near the old normal of 14 days before UHI PHL has been close or below that figure in 2014 (19) / 2009 (15) / 2004 (9) / 2000 (10) / 1996 (7) and 1992 (14)

I don't know if I'd agree that there's been a substantial change in the UHI in Philadelphia. The population was over 1 million by 1890, and over 2 million by 1950.

[ChescoWx]

So while we often talk about the chilling adjustments done to older data for their biases. Where is the cooling UHI adjustments for PHL???? I am told NCEI accounts for known UHI bias. Do we think there is no UHI impact at PHL?? Tell me what I am missing as I know you will! LOL!!!

Below is an analysis of the PHL Airport average annual temperature from 1941 through 2023. I have overlaid the adjusted NCEI temperatures vs the actual reported averages. Why in the last 30 years have the PHL Airport Temps been adjusted upward in 19 of the last 30 years despite UHI?? And the overall cumulative adjustments over those years has been an overall net upward adjustment of 3.45 degrees in PHL actual reported temps. Thoughts????

[ChescoWx]

UHI post obs adjustments by year

[chubbs]

18 hours ago, ChescoWx said:

Because we actually do have the data let's review Charlie's statement that "the older stations with longer records: GlenmooreCoop, Honey Brook and Coatesville,all have a similar and increasing level of 90F days over multiple decades"

Well the actual data Charlie references is below (the yellow highlights are incomplete decades) However, in reality all of the mentioned stations they are the opposite of trending toward an increasing level of 90 degree days. In fact they have trended downward in 90+ days in the complete decades since the 1980's!! Again so different from the UHI problems at PHL. But overall absolutely no clear trend -simply cyclical changes by decade as we have always seen.

Sorry Paul, your handwaving isn't convincing, The three stations averaged (Glenmoore, Honey Brook and Coatesville 2W) have a clear uptrend, supporting my previous statement. The high elevation stations the coop data doesn't support the results you obtain.

I didn't discuss Coatesville 1SW, as its not a high elevation station, but now that you have brought it up. The high number of 90F days in the early portion of its record are not supported by other coop sites. A good argument for bias correction.

[chubbs]

20 hours ago, ChescoWx said:

This is not difficult Charlie the bias in the overall Chesco data is as of the last couple years now actually biased to the warmer lower elevation locales not the higher! In 2023 there are 11 lower elevation spots vs 6 higher. This is why we now have split the data to account for such biases.

Apparently it is difficult for you to detect bias in your own analysis.  The station additions after 2000 have fewer 90F days than the stations that make up your network before 2000 (see Table below). That fact biases the results.  Its easy to get a rough estimate of the impact of station mix change by holding 90F days constant at each stations average level for each year the station was active. If there was no station mix bias you would get a flat trend with time since each station is being held constant.

Per chart below, station mix changes after 2000 have a large impact. The changes in station mix alone would drop the number of 90F days from around 15 between the 1950s and 1990s to a little over 8 in the 2020s. As I expected, the changing station mix is driving your results not climate trends. You should repeat this analysis with the low elevation stations. Just looking at the low elevation station results for 2023, the same station mix problem appears to be present.

Of course stations are always changing as old ones drop out and new ones start up. NOAA and other experts have developed methods to account for station mix changes. If you don't employ the proper methods your results will be biased. Doubly important to follow proven methods if you aren't aware of your own bias.