Cyclical or Natural Predictable Climate Change Forum

[GaWx]

10 hours ago, Roger Smith said:

Note also, if that cycle has a solar variation connection, the solar cycles were longer from 1870 to 1905 than during the stronger regular cycles of the 20th century, and you'll note that 1876 (year 8), 1887 (year 8), 1899 (year 9) are all warm peaks rather than year 10 in those first three periods. Using them would create an average a little over 24.0 C and would yield an overall cycle of 11.2 years which might begin to manifest again if we get a few consecutive weak solar cycles separated by 12-13 years (like 1870, 1883, 1893, 1905, 1917). 

Solar maxima since 1917 have been 1928, 1937, 1947, 1957, 1968, 1979, 1989, 2001, a double weak peak 2012-15, and the current developing peak expected to hit maximum in 2024-25. 

The pattern of solar activity has been generally following a trend of 5-8 regular strong cycles about ten years apart, separated by 2-4 weaker cycles 12-14 years apart. The Maunder minimum was a longer and more profound lack of activity, otherwise, according to Schove's index based on auroral reports before the observational age began around 1610, the Sun has been behaving in those irregular two-phase modes. Stronger cycles occurred 1718-1787 and 1838-1870. The interval between those is known as the Dalton minimum. Other strong pulses of solar activity are believed to have occurred in the 14th and 16th centuries. Much of the 15th century generated weaker activity and is known as the Sporer minimum. 

The shallower minimum including the 1883, 1893 and 1905 peaks does not have a widely accepted name, perhaps it could be called the Edison minimum or the Curie minimum. It was in fact almost identical to the Dalton (peaks 1801, 1816, 1829) if perhaps 10 to 20 per cent more active. This current downturn is often called the Gleissberg minimum and so far is keeping pace with the Dalton and "Edison/Curie" episodes. It has not turned out to be Maunder 2.0 as some had predicted or speculated. It is a bit stronger than the Sporer minimum also. 

 Whereas cycle 24 met expectations of being a weak cycle and was easily the weakest since the late 1800s/early 1900s weak period, cycle 25 (especially during 2022-2023) has been significantly exceeding predictions to be similar or even a bit weaker than 24:

https://en.m.wikipedia.org/wiki/Solar_cycle_25#/media/File%3ASolar_Cycle_25_prediction_and_progression.png

 

"The current solar cycle, known as Solar Cycle 25, has been full of activity, more so than expected. Scientists at the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center in Boulder, Colorado, have already tracked more sunspots than those counted at the peak of the previous cycle."

https://amp.cnn.com/cnn/2023/07/14/world/solar-maximum-activity-2024-scn/index.html

 

[Roger Smith]

Thanks, maybe a repeat of the 1893-94 peak which was a bit stronger than either 1883 or 1905(-07) within that particular downturn. 

By the way, if you can edit your post, "Universal Time" should be Year, no?

[Roger Smith]

To the earlier post, urban heat island is definitely a real phenomenon, you can measure its strength by driving a mobile thermometer through the urban-rural boundary on a clear night. The concept of reducing urban temperature series by subtracting u.h.i. is not a skeptic dodge as perhaps implied, but in fact is practised by even the UK Met Office with the CET series. Nobody would ever accuse them of being skeptics. I've already said I am not a skeptic, I just want to establish what's actually happening and why. I don't doubt that there is a significant human warming signal. I do doubt that we fully understand how it takes place, but I do think it is largely understood, just a matter of ironing out some details. 

I don't think anybody (here at least) is arguing that urban heat islands are being confused with AGW. The argument is more subtle. Maybe AGW has an escaped urban heat component, when the heat islands dissipate heat during windy weather, it enters the larger atmosphere. That however does not make it different from human-caused, it's more of a question of exactly how humans are causing the AGW signal. It might not lead to any different conclusions about mitigation. 

[Typhoon Tip]

Jesus Christ  “AGW” is a planetary integral.  UHI’s are negligible in comparative scale  

yeah … big cities are why there’s marine heat waves threatening to collapse the oceanic biome, why there are methane hydrate blowouts erupting through Siberian permafrost… ,state sized ice sheet calving events and measured oceanic circulation velocity shortening because of flux disruption in the  thermal haline mass distribution. 

This may be more directed to the straw man but I grow tired of reading or hearing this from people - like the ethical scientific ambit doesn’t know the difference and must be conflating UHI effect with the whole world - got it. 

By the way, UHI has increased right along with CC.  Just like heat waves have also increased in duration and zenith … If anything AGW is causing UHIs to grow hotter … not the other way around 
 

 

[GaWx]

6 hours ago, Roger Smith said:

Thanks, maybe a repeat of the 1893-94 peak which was a bit stronger than either 1883 or 1905(-07) within that particular downturn. 

By the way, if you can edit your post, "Universal Time" should be Year, no?

Good catch! I have no idea why it says UT.

[TheClimateChanger]

On 7/17/2023 at 7:59 PM, Roger Smith said:

To the earlier post, urban heat island is definitely a real phenomenon, you can measure its strength by driving a mobile thermometer through the urban-rural boundary on a clear night. The concept of reducing urban temperature series by subtracting u.h.i. is not a skeptic dodge as perhaps implied, but in fact is practised by even the UK Met Office with the CET series. Nobody would ever accuse them of being skeptics. I've already said I am not a skeptic, I just want to establish what's actually happening and why. I don't doubt that there is a significant human warming signal. I do doubt that we fully understand how it takes place, but I do think it is largely understood, just a matter of ironing out some details. 

I don't think anybody (here at least) is arguing that urban heat islands are being confused with AGW. The argument is more subtle. Maybe AGW has an escaped urban heat component, when the heat islands dissipate heat during windy weather, it enters the larger atmosphere. That however does not make it different from human-caused, it's more of a question of exactly how humans are causing the AGW signal. It might not lead to any different conclusions about mitigation. 

I should clarify. I'm not a skeptic of the urban heat island effect per se, but rather I'm a skeptic of the theory that it is a significant driver of the global changes that have been observed.

Actually, noted climate change skeptic, Dr. Roy Spencer, had an interesting analysis of the urban heat island effect back in March. His chart, which passes the eyeball test to me, suggests the effect is greatest as population increases at low density and then gradually decreases (although still positive) as population density increases. Interestingly, the chart also suggests that the effect has been decreasing over time. In other words, there was a more significant positive difference in temperature between densely populated urban areas and remote rural locations in the late 19th century than in the 21st century.

Source: https://www.drroyspencer.com/2023/03/

While not framed this way by Dr. Spencer (for obvious reasons, given his skepticism), this actually gives credence and support to a negative temperature trend due to UHI for certain locations - namely those that have been super densely populated since the late 19th century (i.e., places like New York and Chicago). If the difference in temperature was greater in the 1800s in densely populated urban sites than zero population density locations, then it stands to reason that the UHI effect has actually imparted a small negative component to the trend for such sites. In other words, if the UHI effect has decreased for a given population density and those sites have not experienced an appreciable increase in population density over the period, then there must be a negative trend component attributable to the effect.

This might seem to be a counterintuitive finding - and Dr. Spencer expressed surprise towards it - but several compelling theories were raised in the comments. My thinking is it's probably related to improved siting of urban stations. In the 1800s, the urban stations were almost exclusively sited in window sills (yes, you read that correctly) or on rooftops. Now they are mostly ground-based, often in an area of green space or parkland, or at an airport with more open grass than the dense urban core. But some other interested theories were offered in the comments - perhaps increased tree canopy cover, better building materials / insulation preventing loss of heat to the environment, and/or the advent of skyscrapers has led to more heat being trapped higher in the atmosphere as opposed to at the level of the thermometer. Those theories would suggest the UHI effect itself has been decreased, whereas my initial thought was simply improved temperature recording - i.e., there hasn't been a decrease in UHI, but rather some of the temperature difference which was previously ascribed to UHI was actually just a result of poor station siting and not actually UHI effect. In reality, it may be a combination of both of these factors.

[Roger Smith]

I don't strongly disagree with any of the points raised. just trying to assess the most accurate intensity of urban heat island components of recent warming trends. 

Anyway, the OP started this thread to have a discussion of natural variability which continues to exist and which modulates the climate as it warms. So I would hope we can return to that focus and discuss that 11-year signal in summer temperatures in NYC which I would assume would probably apply to a much larger region of eastern and perhaps central North America. 

[TheClimateChanger]

Ryan Maue seems to be suggesting that most of the warming in Phoenix is due to the urban heat island effect - what do you guys think?

 

 

[TheClimateChanger]

I did a little comparison between PHX and Grand Canyon Airport (GCN) - the latter of which is quite literally in the middle of nowhere when it comes to human population density. Unfortunately, records for GCN were only available back to 1997 for GCN, but that still allowed for about a quarter century of data.

From 1997-2022, I calculated a warming trend of 7.3F/century for daily maxima at GCN, 4.3F/century for daily minima, and 5.7F/century for daily mean temperature.

For the same period at PHX, I calculated a warming trend of 10.0F/century for daily maxima, 7.8F/century for daily minima, and 8.8F/century for daily mean temperature.

While the relatively short period of analysis makes drawing definitive conclusions a bit challenging, a couple of observations. It is warming at an alarming rate at both sites; however, PHX does show a residual warming trend of about 3.0F/century compared to GCN. This residual may be related to a growing urban heat island effect. However, Dr. Spencer's research would suggest that, at some point, the UHI effect will essentially "max out" and stop being a significant contributor to the trend.

Second, maximum temperatures have climbed more than minimum temperatures at both sites over this interval. This is inconsistent with UHI effect. Mr. Maue has some graphics showing a collapse in the diurnal temperature range (DTR) at Phoenix since the mid 20th century. This data suggests that trend has reversed somewhat since the late 1990s, and DTR has increased by a small bit since that time.

Lastly, I feel it is disingenuous to compare the PHX trend to the globally averaged trend and suggest all of the excess is due to UHI. It should be clear that the regional climate around PHX is warming considerably faster than the global average.

 

[roardog]

Phoenix had a “cool” June so I wonder if that plays a role somewhat. Does that help delay the moisture from the monsoon a little which in turns allows it to get a bit hotter now in late July? I’m not terribly familiar with the desert SW climate so it’s just something I was thinking about. 

[Roger Smith]

A lot depends on site characteristics for airport weather stations. If the instruments are close to tarmac and parking lots, those might be larger factors than urban heat island if the airport is not surrounded by urban areas. Shannon airport in Ireland is essentially a rural location but Irish weather folk seem to believe it has a 1 C bias in hot weather due to the instruments being very close to tarmac and parking lots. DCA is another such location. 

I would imagine that Phoenix would be running near 118F even if there was no human presence, in this weather pattern, but the nights might not be quite as warm maybe? 

A good station to check for long-term unaffected (by urban effect) trends might be Bryce Canyon airport in Utah or Canyonlands airport near Moab. Neither of those locations has a very large airport around, and they are miles out of town (for Bryce Canyon, the nearby urban locations are all very small, Panguitch UT might have a tiny heat island; for Moab, Canyonlands is ten miles out of town and Moab itself probably has a very small heat island. 

Another location with no heat island potential would be hanksville UT which is east of Capitol Reef NP. The village is just a few houses and a gas station and motel, it would not have an urban heat island at all. 

[donsutherland1]

On 7/19/2023 at 10:38 AM, TheClimateChanger said:

Ryan Maue seems to be suggesting that most of the warming in Phoenix is due to the urban heat island effect - what do you guys think?

 

 

He’s wrong. The literature notes that UHI is strongest at night, not day. UHI is skewing low temperatures, but having only a small impact on high temperatures.

[chubbs]

Barbie says don't blame UHI or thermometers next to AC units

 

 

[ChescoWx]

This does not look very warm to my eyes despite the alarmist talk of never before seen high temperature heat....

[TheClimateChanger]

1 hour ago, ChescoWx said:

This does not look very warm to my eyes despite the alarmist talk of never before seen high temperature heat....

Fake news.