Occasional Thoughts on Climate Change

[tacoman25]

24 minutes ago, bluewave said:

If you look at the JJA 20 year trend from 1995 to 2024, then the high/low trend is nearly identical for both stations. The minimums are rising at a faster pace for both locations. Obviously, Phoenix gets the most attention since the actual temperatures are significantly higher. But the temperature increase at both locations has been the same even at significantly different altitudes.

https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/city/time-series/USW00003103/tmin/3/8/1995-2024?trend=true&trend_base=10&begtrendyear=1995&endtrendyear=2025&filter=true&filterType=binomial

1995-2024 temperature trend 

Phoenix……max…+0.8°F/Decade….min…+1.0°F/Decade

Flagstaff…..max…+0.7°F/Decade…min…..+.1.1°F/Decade

 

That's 30 years. And obviously the exact starting point matters...depending on if you start in 1970, 1980, 1995, 2005, 2010 you'll get differing trend numbers.

But again, July/August is the primary monsoon season (rarely does it start until late June/early July, sometimes not until mid July). Including June makes about as much since if not less than including September.

If I go as far back as the data allows (1933) and plot JJAS avg temp trend for Flagstaff, it's .3F/decade. For Phoenix, it's twice as much with .6F/decade. Same trend for JJA if you prefer that.

[donsutherland1]

21 minutes ago, GaWx said:

 Chris,

 Don and I have had discussions about the UHI portion of the warming at Phoenix over the last 30-40+ years due to the tremendous population growth. We agreed that the UHI portion isn’t at all insignificant if I’m recalling this correctly.

@donsutherland1

Yes, that’s correct. Phoenix has a pronounced UHI effect. One sees it particularly in the explosive increase in 90 or above low temperatures.

[tacoman25]

All trendlines aside, in practical, very recent terms:

- Phoenix was 3 degrees above their long term average in July 2025. Flagstaff was exactly average.

- Phoenix was a ridiculous 9 degrees above their long term mean in July 2023. That same month, Flagstaff was about 5 degrees above theirs.

- Phoenix hasn't had a June below their long term mean since 2009. Flagstaff's most recent was 2023.

- Phoenix's hottest year on record was 2024. Flagstaff's was 1981.

 

[tacoman25]

3 minutes ago, donsutherland1 said:

Yes, that’s correct. Phoenix has a pronounced UHI effect. One sees it particularly in the explosive increase in 90 or above low temperatures.

The last time Phoenix had an August with average low temps below their long term mean was 1990.

Flagstaff did it in 2017, 2016, and 2014. Along with a bunch of other years since 1990.

[bluewave]

13 minutes ago, tacoman25 said:

That's 30 years. And obviously the exact starting point matters...depending on if you start in 1970, 1980, 1995, 2005, 2010 you'll get differing trend numbers.

But again, July/August is the primary monsoon season (rarely does it start until late June/early July, sometimes not until mid July). Including June makes about as much since if not less than including September.

If I go as far back as the data allows (1933) and plot JJAS avg temp trend for Flagstaff, it's .3F/decade. For Phoenix, it's twice as much with .6F/decade. Same trend for JJA if you prefer that.

The 2020s has produced unprecedented summer warmth for both locations. Flagstaff and Phoenix both had their warmest summers on record in 2024 by a significant margin. All the 2020s summers have been in the top 10 for warmth which has never happened before.

Time Series Summary for Flagstaff Area, AZ (ThreadEx) 10 Warmest Summers dense rank sorting by temperature 
Click column heading to sort ascending, click again to sort descending.

1	2024	68.4	0
2	1981	66.6	0
3	2002	66.3	0
4	2025	66.2	13
5	2021	66.1	0
6	2020	65.8	0
-	2007	65.8	0
-	1974	65.8	0
-	1940	65.8	0
7	2018	65.6	0
8	2022	65.4	0
-	2008	65.4	0
-	1980	65.4	0
9	2012	65.3	0
-	1946	65.3	0
10	2023	65.2	0
-	2017	65.2	0
-	1996	65.2	0
-	1977	65.2	0

 

Time Series Summary for Phoenix Area, AZ (ThreadEx)10 Warmest Summers dense rank sorting by temperature  
Click column heading to sort ascending, click again to sort descending.

1	2024	98.9	0
2	2023	97.0	0
3	2025	96.7	13
-	2020	96.7	0
4	2015	95.1	0
-	2013	95.1	0
5	2019	94.9	0
-	2007	94.9	0
6	2011	94.8	0
-	2002	94.8	0
-	1981	94.8	0
7	2022	94.7	0
8	2017	94.6	0
-	2016	94.6	0
-	2003	94.6	0
9	2006	94.5	0
10	1989	94.4	0
-	1988	94.4	0

[rclab]

12 minutes ago, bluewave said:

The 2020s has produced unprecedented summer warmth for both locations. Flagstaff and Phoenix both had their warmest summers on record in 2024 by a significant margin. All the 2020s summers have been in the top 10 for warmth which has never happened before.

Time Series Summary for Flagstaff Area, AZ (ThreadEx) 10 Warmest Summers dense rank sorting by temperature 
Click column heading to sort ascending, click again to sort descending.

1	2024	68.4	0
2	1981	66.6	0
3	2002	66.3	0
4	2025	66.2	13
5	2021	66.1	0
6	2020	65.8	0
-	2007	65.8	0
-	1974	65.8	0
-	1940	65.8	0
7	2018	65.6	0
8	2022	65.4	0
-	2008	65.4	0
-	1980	65.4	0
9	2012	65.3	0
-	1946	65.3	0
10	2023	65.2	0
-	2017	65.2	0
-	1996	65.2	0
-	1977	65.2	0

 

Time Series Summary for Phoenix Area, AZ (ThreadEx)10 Warmest Summers dense rank sorting by temperature  
Click column heading to sort ascending, click again to sort descending.

1	2024	98.9	0
2	2023	97.0	0
3	2025	96.7	13
-	2020	96.7	0
4	2015	95.1	0
-	2013	95.1	0
5	2019	94.9	0
-	2007	94.9	0
6	2011	94.8	0
-	2002	94.8	0
-	1981	94.8	0
7	2022	94.7	0
8	2017	94.6	0
-	2016	94.6	0
-	2003	94.6	0
9	2006	94.5	0
10	1989	94.4	0
-	1988	94.4	0

Amazing BW ….. 3 of the top 5 occurred within the last 4 years. As always …..

[tacoman25]

43 minutes ago, bluewave said:

The 2020s has produced unprecedented summer warmth for both locations. Flagstaff and Phoenix both had their warmest summers on record in 2024 by a significant margin. All the 2020s summers have been in the top 10 for warmth which has never happened before.

Time Series Summary for Flagstaff Area, AZ (ThreadEx) 10 Warmest Summers dense rank sorting by temperature 
Click column heading to sort ascending, click again to sort descending.

1	2024	68.4	0
2	1981	66.6	0
3	2002	66.3	0
4	2025	66.2	13
5	2021	66.1	0
6	2020	65.8	0
-	2007	65.8	0
-	1974	65.8	0
-	1940	65.8	0
7	2018	65.6	0
8	2022	65.4	0
-	2008	65.4	0
-	1980	65.4	0
9	2012	65.3	0
-	1946	65.3	0
10	2023	65.2	0
-	2017	65.2	0
-	1996	65.2	0
-	1977	65.2	0

 

Time Series Summary for Phoenix Area, AZ (ThreadEx)10 Warmest Summers dense rank sorting by temperature  
Click column heading to sort ascending, click again to sort descending.

1	2024	98.9	0
2	2023	97.0	0
3	2025	96.7	13
-	2020	96.7	0
4	2015	95.1	0
-	2013	95.1	0
5	2019	94.9	0
-	2007	94.9	0
6	2011	94.8	0
-	2002	94.8	0
-	1981	94.8	0
7	2022	94.7	0
8	2017	94.6	0
-	2016	94.6	0
-	2003	94.6	0
9	2006	94.5	0
10	1989	94.4	0
-	1988	94.4	0

Right, no one is disputing it's been hot in Flagstaff. It just hasn't warmed as much as Phoenix, as those stats clearly show. It's a distinct difference.

- Two of Flagstaff's top 3 warmest summers happened more than 20 years ago. Meanwhile, those same two summers are tied for 6th hottest in Phoenix, and their three hottest are the last three summers.

- Flagstaff has 5 summers among their 10 warmest that occurred 2007 or earlier. Phoenix has 2.

- Flagstaff has a total of 7 20th century summers on their list. Phoenix has 3.

- Phoenix's hottest summer is more than 4 degrees warmer than their hottest 20th century summer. Flagstaff's is less than 2 degrees warmer.

[bluewave]

1 hour ago, GaWx said:

 Chris,

 Don and I have had discussions about the UHI portion of the warming at Phoenix over the last 30-40+ years due to the tremendous population growth. We agreed that the UHI portion isn’t at all insignificant if I’m recalling this correctly.

@donsutherland1

UHI acts as an amplifier of mostly the low temperatures in and around Phoenix leading to the rapid increase in 80° minimums there. But the rapid increase in 100°+ maxes is evenly distributed across, urban, suburban, and rural locations. It’s the rapid warming of the planet which is driving the increasing intensity of the heat.

So the UHI acts to keep the urban centers warmer at night than the outlying areas. But both areas as seeing steep increases in the minimum and maximum temperatures. So without the background warming of the climate, the UHI alone wouldn’t be nearly as significant. 

 

[Typhoon Tip]

15 hours ago, bluewave said:

UHI acts as an amplifier of mostly the low temperatures in and around Phoenix leading to the rapid increase in 80° minimums there. But the rapid increase in 100°+ maxes is evenly distributed across, urban, suburban, and rural locations. It’s the rapid warming of the planet which is driving the increasing intensity of the heat.

So the UHI acts to keep the urban centers warmer at night than the outlying areas. But both areas as seeing steep increases in the minimum and maximum temperatures. So without the background warming of the climate, the UHI alone wouldn’t be nearly as significant. 

 

It just gets exhausting trying to explain this to the people that can’t synthesize global perspectives; probably as a native intellectual limitation. Which unfortunately is precisely what is needed if somebody’s going to understand how global warming works  

Dimes to donuts the majority of the people in the denier frame of mind are narrow perspective types

[chubbs]

12 hours ago, Typhoon Tip said:

It just gets exhausting trying to explain this to the people that can’t synthesize global perspectives; probably as a native intellectual limitation. Which unfortunately is precisely what is needed if somebody’s going to understand how global warming works  

Dimes to donuts the majority of the people in the denier frame of mind are narrow perspective types

Yes, UHI and global warming are both happening. The presence of one doesn't diminish the other. This thread/board is littered with whataboutism. What about this, what about that. Many things can be true at the same time. That doesn't change the big picture. Scientists from the 1970s would not be surprised by the warmer world we have today or that Phoenix has a heat island.

[FPizz]

12 hours ago, Typhoon Tip said:

It just gets exhausting trying to explain this to the people that can’t synthesize global perspectives; probably as a native intellectual limitation. Which unfortunately is precisely what is needed if somebody’s going to understand how global warming works  

Dimes to donuts the majority of the people in the denier frame of mind are narrow perspective types

How come if lows are higher, that doesn't make highs also higher since the starting point for the day is already a higher temp?

When I see reports of some cities around the world planting more trees in cities and then saying high temps went down by 5 degrees during the day for example, is that not showing that UHI also effects the high temps?  

Not denying anything, but just wondering.  Especially about the 2nd question because I see that talked about on many "green" type forums and how many cities should adopt that to lower daytime temps (obviously because of more shade).  

[Typhoon Tip]

3 hours ago, FPizz said:

How come if lows are higher, that doesn't make highs also higher since the starting point for the day is already a higher temp?

When I see reports of some cities around the world planting more trees in cities and then saying high temps went down by 5 degrees during the day for example, is that not showing that UHI also effects the high temps?  

Not denying anything, but just wondering.  Especially about the 2nd question because I see that talked about on many "green" type forums and how many cities should adopt that to lower daytime temps (obviously because of more shade).  

anyway... the bold is a good question.  There's a lot of complexity in there but the simplest explanation is water vapor.   When there is more water vapor that has been heated, the total atmosphere holds more energy that way - needs more energy to keep water in gaseous form.  That keeps the temperature up at night.  However, in the day, it can also hold the temp down some, because it takes more energy to heat WV than dry air.  The complexity is the relativity of those two.  It's still 100/72 on July 10 in Boston ...and that's enough to roast one's nuts.. but, a profile of 104/66 has about the same thermodynamic quotient.  

Ha ha ... wasn't intending to be all guilty like.  It's really more a frustration pointed at the general circumstance.   It's a numbers game.   Let's think about this logically for a minute.  There are 8+ billion human brains walking the Earth.  What are the odds that 100% of them are completely capable of objectively intellectualizing CC, and then responding to it with a cogent sanity that is reflected in their response to it and behaviors after the fact?   

The answer is 0%   .... In other words, there is 0% chance that 100% will get it.  

So that leaves us in a predicament that some portion of 8+ billion are incapable of getting it.   What is that number?    If it is even 10 percent, we're still  talking 800,000,000+ brains powered by carbon fartin' industrialized environmental destruction. This predisposition leads to reticence to the concepts and acceptance of CC caused by carbon fartin', less likely to react proactively in prevention.  And, 800,000,000+ is still enough people that even if the remaining 7+ billion were to completely accept and adapt their technology and principles of living around preventing anthropomorphic GW, we're all still doomed...  They are doomed because 800,000,000+ is enough to ensure environmental collapse still takes place in spite of everyone else. It's kind of a scary untenable scenario really.

 

[FPizz]

1 hour ago, Typhoon Tip said:

anyway... the bold is a good question.  There's a lot of complexity in there but the simplest explanation is water vapor.   When there is more water vapor that has been heated, the total atmosphere holds more energy that way - needs more energy to keep water in gaseous form.  That keeps the temperature up at night.  However, in the day, it can also hold the temp down some, because it takes more energy to heat WV than dry air.  The complexity is the relativity of those two.  It's still 100/72 on July 10 in Boston ...and that's enough to roast one's nuts.. but, a profile of 104/66 has about the same thermodynamic quotient.  

Ha ha ... wasn't intending to be all guilty like.  It's really more a frustration pointed at the general circumstance.   It's a numbers game.   Let's think about this logically for a minute.  There are 8+ billion human brains walking the Earth.  What are the odds that 100% of them are completely capable of objectively intellectualizing CC, and then responding to it with a cogent sanity that is reflected in their response to it and behaviors after the fact?   

The answer is 0%   .... In other words, there is 0% chance that 100% will get it.  

So that leaves us in a predicament that some portion of 8+ billion are incapable of getting it.   What is that number?    If it is even 10 percent, we're still  talking 800,000,000+ brains powered by carbon fartin' industrialized environmental destruction. This predisposition leads to reticence to the concepts and acceptance of CC caused by carbon fartin', less likely to react proactively in prevention.  And, 800,000,000+ is still enough people that even if the remaining 7+ billion were to completely accept and adapt their technology and principles of living around preventing anthropomorphic GW, we're all still doomed...  They are doomed because 800,000,000+ is enough to ensure environmental collapse still takes place in spite of everyone else. It's kind of a scary untenable scenario really.

 

Thanks, I figured it was something like that.  It is pretty amazing how that happens that it can even out for the high temps.  

Something like this I picture see posted often in numerous ways showing the difference, in a city setting,  how having trees lowers temps everywhere from the air to the ground we walk on (and has been done around the world proving it works).  Wouldn't this be an example of UHI during the day?  Or, would we say the temps on the lower picture are not accurate for the air since it is under a canopy of trees?  So the lower picture is like Central Park temps which people in my forum argue about every day of the week and the top picture is actually the accurate one for temps?  Here is where this pic was from https://symsoil.medium.com/trees-climate-change-and-community-878280498546   I see this movement talked about often though for cities and it would be nice if adopted by many more.  

  

[TheClimateChanger]

5 minutes ago, FPizz said:

Thanks, I figured it was something like that.  It is pretty amazing how that happens that it can even out for the high temps.  

Something like this I picture see posted often in numerous ways showing the difference, in a city setting,  how having trees lowers temps everywhere from the air to the ground we walk on (and has been done around the world proving it works).  Wouldn't this be an example of UHI during the day?  Or, would we say the temps on the lower picture are not accurate for the air since it is under a canopy of trees?  So the lower picture is like Central Park temps which people in my forum argue about every day of the week and the top picture is actually the accurate one for temps?  Here is where this pic was from https://symsoil.medium.com/trees-climate-change-and-community-878280498546   I see this movement talked about often though for cities and it would be nice if adopted by many more.  

  

That's a stupid graphic measuring surface temperature, not near surface air temperatures. Certainly, being shaded can cool the air temperature as well [not to that extent], but surface air temperatures are supposed to be observed in a location free from shading and obstructions.

[TheClimateChanger]

2 hours ago, Typhoon Tip said:

anyway... the bold is a good question.  There's a lot of complexity in there but the simplest explanation is water vapor.   When there is more water vapor that has been heated, the total atmosphere holds more energy that way - needs more energy to keep water in gaseous form.  That keeps the temperature up at night.  However, in the day, it can also hold the temp down some, because it takes more energy to heat WV than dry air.  The complexity is the relativity of those two.  It's still 100/72 on July 10 in Boston ...and that's enough to roast one's nuts.. but, a profile of 104/66 has about the same thermodynamic quotient.  

Ha ha ... wasn't intending to be all guilty like.  It's really more a frustration pointed at the general circumstance.   It's a numbers game.   Let's think about this logically for a minute.  There are 8+ billion human brains walking the Earth.  What are the odds that 100% of them are completely capable of objectively intellectualizing CC, and then responding to it with a cogent sanity that is reflected in their response to it and behaviors after the fact?   

The answer is 0%   .... In other words, there is 0% chance that 100% will get it.  

So that leaves us in a predicament that some portion of 8+ billion are incapable of getting it.   What is that number?    If it is even 10 percent, we're still  talking 800,000,000+ brains powered by carbon fartin' industrialized environmental destruction. This predisposition leads to reticence to the concepts and acceptance of CC caused by carbon fartin', less likely to react proactively in prevention.  And, 800,000,000+ is still enough people that even if the remaining 7+ billion were to completely accept and adapt their technology and principles of living around preventing anthropomorphic GW, we're all still doomed...  They are doomed because 800,000,000+ is enough to ensure environmental collapse still takes place in spite of everyone else. It's kind of a scary untenable scenario really.

 

Excellent post, Tip. The part I emboldened in is an excellent point.  One I have made numerous times. When you factor that into the equation, there is NO central US warming hole. It disappears. Current summers FEEL much hotter than summers of the past, including the Dust Bowl, which were the driest (least humid) on record. And while some may say "heat index" is subjective, it's really just a proxy for the wet bulb temperature reading. And that can, in fact, become deadly, even at relatively modest dry bulb temperatures with full (or near full) saturation.

Anyways, I often see certain people who deny (some people on here get offended with the term "denier" even though they have used that term profusely in the past, but I digress)... people who deny climate change often say highs are of more value, because lows are more affected by UHI. I would actually argue the exact opposite, and say high temperature readings are more impacted by siting/exposure characteristics and equipment, and low temperatures give us a better look at actual trends.

[TheClimateChanger]

17 minutes ago, TheClimateChanger said:

Excellent post, Tip. The part I emboldened in is an excellent point.  One I have made numerous times. When you factor that into the equation, there is NO central US warming hole. It disappears. Current summers FEEL much hotter than summers of the past, including the Dust Bowl, which were the driest (least humid) on record. And while some may say "heat index" is subjective, it's really just a proxy for the wet bulb temperature reading. And that can, in fact, become deadly, even at relatively modest dry bulb temperatures with full (or near full) saturation.

Anyways, I often see certain people who deny (some people on here get offended with the term "denier" even though they have used that term profusely in the past, but I digress)... people who deny climate change often say highs are of more value, because lows are more affected by UHI. I would actually argue the exact opposite, and say high temperature readings are more impacted by siting/exposure characteristics and equipment, and low temperatures give us a better look at actual trends.

Speaking of lows:

 

[FPizz]

59 minutes ago, TheClimateChanger said:

That's a stupid graphic measuring surface temperature, not near surface air temperatures. Certainly, being shaded can cool the air temperature as well [not to that extent], but surface air temperatures are supposed to be observed in a location free from shading and obstructions.

That shows near surface too (the top temperature on it) and there are a million examples online from sites you probably whack to.  I will wait for Tips answer since he is actually smart and has the credentials and you really didn't answer anything at all.

[TheClimateChanger]

25 minutes ago, FPizz said:

That shows near surface too (the top temperature on it) and there are a million examples online from sites you probably whack to.  I will wait for Tips answer since he is actually smart and has the credentials and you really didn't answer anything at all.

Ok, well, I don't believe that. It's not 10C (18F!) warmer in a sunny neighborhood versus a shady one if the thermometer is properly sheltered or aspirated. My car thermometer doesn't register anywhere near that difference and it's housed like a foot or so above the asphalt.

[Typhoon Tip]

2 hours ago, FPizz said:

Thanks, I figured it was something like that.  It is pretty amazing how that happens that it can even out for the high temps.  

Something like this I picture see posted often in numerous ways showing the difference, in a city setting,  how having trees lowers temps everywhere from the air to the ground we walk on (and has been done around the world proving it works).  Wouldn't this be an example of UHI during the day?  Or, would we say the temps on the lower picture are not accurate for the air since it is under a canopy of trees?  So the lower picture is like Central Park temps which people in my forum argue about every day of the week and the top picture is actually the accurate one for temps?  Here is where this pic was from https://symsoil.medium.com/trees-climate-change-and-community-878280498546   I see this movement talked about often though for cities and it would be nice if adopted by many more.  

  

 

The idea of tree and/or vegetation modulation on heat is again water vapor related.   There's also a component of straight shade helping to block the sun.  These two factors are important in that whole idea.   

Vegetation "sweats."  It's called transpiration when it sources from from plants. Water evaporates from that source, and that lowers the temperature.  Although that does add water to the atmosphere in the form of vapor, but you'll end up with slightly elevated DPs in the vicinity of vegetation, with slightly lowered temps.   As that is ongoing, the cooler resulting air is drawn downward because of course cooler air is denser.  This principle is illustrated well in the bottom photo - although I can't attest to those actual numbers, but in so far as getting the point across.. that's the idea there. Contrasting, the upper photo doesn't have this process. 

This is a local cooling effect, however.  The temperatures in those respective schematics are in the micro meteorology.  Which, per course ... what one experiences in a city/urban setting on a hot day is in fact within a micro-meteorological realm.  That would be neighborhood vs neighborhood... Unless the given cityscape is pervasively and comprehensively forested and so forth, it calls into questions the efficacy of offsetting a UHI effects.  The collection of sun-exposed concrete surfaces, such as downtown, parking lots... the edifices of the buildings too, to mention the heat output from industrial scaled AC exhaust.   It's a tricky math.   Lot of summing multiple separate integrals in that calculus.

My personal belief is that the UHI capacity goes up with warming CC, and goes back down with cooling CC.  I suspect the growth may not be entirely linear, either ( as in going up together.  Because different materials have different storing capacitance ... so that changes the contribution into the "UHI bubble" based on different energy source and sinks.   It's a coupling of material sciences, with atmospheric science, which is not likely trivial.  But intuitively, doesn't seem like that's a swift calculation to make. Just hypothetically... a sunny day in Phoenix AZ on July 10, 1972 may calculated a UHI factor of some 15F over the surrounding country, but that may be closer to 20F in 2025 given the same initial conditions and sunny day.   See, the climate is 1C warmer, but there is a disproportionately larger UHI response.