Chapter 6 – Temperature Changes in the United States of the U.S. Global Change Research Program’s recently published Climate Science Special Report (2017) clearly shows and discusses, under the heading of “6.1.2 Temperature Extremes”, how temperature extremes for the contiguous United States have become more moderate over the last 118 years, with the coldest daily temperatures warming and the warmest daily temperatures cooling. In other words, temperature-extreme-related climate in the United States has improved.
TEMPERATURE EXTREMES
Their Figure 6.3 is presented below (click to enlarge):
Figure 6.3 from U.S. GCRP CSSR 2017
The caption for their Figure 6.3 reads:
Observed changes in the coldest and warmest daily temperatures (°F) of the year in the contiguous United States. Maps (top) depict changes at stations; changes are the difference between the average for present-day (1986–2016) and the average for the first half of the last century (1901–1960). Time series (bottom) depict the area-weighted average for the contiguous United States. Estimates are derived from long-term stations with minimal missing data in the Global Historical Climatology Network–Daily dataset.16 (Figure source: NOAA/NCEI).
For those having trouble reading the graphs and maps, see the individual cells below.
Portion of Figure 6.3 from U.S. GCRP CSSR 2017 – Map – Change in Coldest
# # #
Portion of Figure 6.3 from U.S. GCRP CSSR 2017 – Graph – Change in Coldest
# # #
Portion of Figure 6.3 from U.S. GCRP CSSR 2017 – Map – Change in Warmest
# # #
Portion of Figure 6.3 from U.S. GCRP CSSR 2017 – Graph – Change in Warmest
The caption for Table 6.2 reads:
Table 6.2. Observed changes in the coldest and warmest daily temperatures (°F) of the year for each National Climate Assessment region in the contiguous United States. Changes are the difference between the average for present-day (1986–2016) and the average for the first half of the last century (1901–1960). Estimates are derived from long-term stations with minimal missing data in the Global Historical Climatology Network–Daily dataset.16
And for your viewing pleasure, here’s their Table 6.2:
Table 6.2 from U.S. GCRP CSSR 2017
Their Figure 6.4 is below:
Figure 6.4 from U.S. GCRP CSSR 2017
The caption for their Figure 6.4 reads:
Observed changes in cold and heat waves in the contiguous United States. The top panel depicts changes in the frequency of cold waves; the middle panel depicts changes in the frequency of heat waves; and the bottom panel depicts changes in the intensity of heat waves. Cold and heat wave frequency indices are defined in Zhang et al.,15 and the heat wave intensity index is defined in Russo et al.14 Estimates are derived from long-term stations with minimal missing data in the Global Historical Climatology Network–Daily dataset.16 (Figure source: NOAA/NCEI).
The text for that section reads:
6.1.2 Temperature Extremes
Shifts in temperature extremes are examined using a suite of societally relevant climate change indices14 ,15 derived from long-term observations of daily surface temperature.16 The coldest and warmest temperatures of the year are of particular relevance given their widespread use in engineering, agricultural, and other sectoral applications (for example, extreme annual design conditions by the American Society of Heating, Refrigeration, and Air Conditioning; plant hardiness zones by the U.S. Department of Agriculture). Cold waves and heat waves (that is, extended periods of below or above normal temperature) are likewise of great importance because of their numerous societal and environmental impacts, which span from human health to plant and animal phenology. Changes are considered for a spectrum of event frequencies and intensities, ranging from the typical annual extreme to the 1-in-10 year event (an extreme that only has a 10% chance of occurrence in any given year). The discussion focuses on the contiguous United States; Alaska, Hawai‘i, and the Caribbean do not have a sufficient number of long-term stations for a century-scale analysis.
Cold extremes have become less severe over the past century. For example, the coldest daily temperature of the year has increased at most locations in the contiguous United States (Figure 6.3). All regions experienced net increases (Table 6.2), with the largest rises in the Northern Great Plains and the Northwest (roughly 4.5°F [2.5°C]), and the smallest in the Southeast (about 1.0°F [0.6°C]). In general, there were increases throughout the record, with a slight acceleration in recent decades (Figure 6.3). The temperature of extremely cold days (1-in-10 year events) generally exhibited the same pattern of increases as the coldest daily temperature of the year. Consistent with these increases, the number of cool nights per year (those with a minimum temperature below the 10th percentile for 1961–1990) declined in all regions, with much of the West having decreases of roughly two weeks. The frequency of cold waves (6-day periods with a minimum temperature below the 10th percentile for 1961–1990) has fallen over the past century (Figure 6.4). The frequency of intense cold waves (4-day, 1-in-5 year events) peaked in the 1980s and then reached record-low levels in the 2000s.17
Changes in warm extremes are more nuanced than changes in cold extremes. For instance, the warmest daily temperature of the year increased in some parts of the West over the past century (Figure 6.3), but there were decreases in almost all locations east of the Rocky Mountains. In fact, all eastern regions experienced a net decrease (Table 6.2), most notably the Midwest (about 2.2°F [1.2°C]) and the Southeast (roughly 1.5°F [0.8°C]). The decreases in the eastern half of Nation, particularly in the Great Plains, are mainly tied to the unprecedented summer heat of the 1930s Dust Bowl era, which was exacerbated by land-surface feedbacks driven by springtime precipitation deficits and land mismanagement.18 However, anthropogenic aerosol forcing may also have reduced summer temperatures in the Northeast and Southeast from the early 1950s to the mid-1970s,19 and agricultural intensification may have suppressed the hottest extremes in the Midwest.20 Since the mid-1960s, there has been only a very slight increase in the warmest daily temperature of the year (amidst large interannual variability). Heat waves (6-day periods with a maximum temperature above the 90th percentile for 1961–1990) increased in frequency until the mid-1930s, became considerably less common through the mid-1960s, and increased in frequency again thereafter (Figure 6.4). As with warm daily temperatures, heat wave magnitude reached a maximum in the 1930s. The frequency of intense heat waves (4-day, 1-in-5 year events) has generally increased since the 1960s in most regions except the Midwest and the Great Plains.17 ,21 Since the early 1980s (Figure 6.4), there is suggestive evidence of a slight increase in the intensity of heat waves nationwide14 as well as an increase in the concurrence of droughts and heat waves.22
AND NOW FOR THE ODDEST GRAPH IN THE REPORT
After discussing and illustrating how heat waves and daily high temperatures have decreased since the 1930s, the report continues:
Changes in the occurrence of record-setting daily temperatures are also apparent. Very generally, the number of record lows has been declining since the late-1970s while the number of record highs has been rising.23 By extension, there has been an increase in the ratio of the number of record highs to record lows (Figure 6.5). Over the past two decades, the average of this ratio exceeds two (meaning that twice as many high-temperature records have been set as low-temperature records). The number of new highs has surpassed the number of new lows in 15 of the last 20 years, with 2012 and 2016 being particularly extreme (ratios of seven and five, respectively).
Figure 6.5 from U.S. GCRP CSSR 2017
The caption for their Figure 6.5 reads:
Observed changes in the occurrence of record-setting daily temperatures in the contiguous United States. Red bars indicate a year with more daily record highs than daily record lows, while blue bars indicate a year with more record lows than highs. The height of the bar indicates the ratio of record highs to lows (red) or of record lows to highs (blue). For example, a ratio of 2:1 for a blue bar means that there were twice as many record daily lows as daily record highs that year. Estimates are derived from long-term stations with minimal missing data in the Global Historical Climatology Network–Daily dataset.16 (Figure source: NOAA/NCEI).
That graph is so silly it’s laughable. After they present something as nonsensical as that, do they expect us to take the rest of the report seriously?
Of course, those daily record highs and lows happened throughout the year. What they aren’t telling us is that the recent record highs likely occurred least often during the summer months and that they likely occurred most often during winter months.
My Figures 1 and 2 show the seasonal maximum temperatures (TMAX) and minimum temperatures (TMIN) for the contiguous U.S. so that you can see which seasons are showing increases in TMIN and TMAX and what season is showing no increase in TMAX. The data for the graphs in my Figures 1 and 2 can be retrieved through the NOAA webpage here. More specifically, the NOAA data page that includes the monthly TMIN and TMAX in absolute form in deg F used to be available here. Good thing I archived it here
Figure 1
# # #
Figure 2
BACK TO THE CLIMATE SCIENCE SPECIAL REPORT
Of course the “Highlights of the Findings of the U.S. Global Change Research Program Climate Science Special Report” which starts the Executive Summary fails to mention the highs in the 1930s. The 8th paragraph of the Executive Summary reads (their boldface):
Heatwaves have become more frequent in the United States since the 1960s, while extreme cold temperatures and cold waves are less frequent. Recent record-setting hot years are projected to become common in the near future for the United States, as annual average temperatures continue to rise. Annual average temperature over the contiguous United States has increased by 1.8°F (1.0°C) for the period 1901–2016; over the next few decades (2021–2050), annual average temperatures are expected to rise by about 2.5°F for the United States, relative to the recent past (average from 1976–2005), under all plausible future climate scenarios.
I’ll let you comment on that nonsense. That’s it for now.
Have fun in the comments and enjoy the remainder of your day.
STANDARD CLOSING REQUEST
Please purchase my recently published ebooks. As many of you know, this year I published 2 ebooks that are available through Amazon in Kindle format:
- Dad, Why Are You A Global Warming Denier? (For an overview, the blog post that introduced it is here.)
- Dad, Is Climate Getting Worse in the United States? (See the blog post here for an overview.)
To those of you who have purchased them, thank you. To those of you who will purchase them, thank you, too.
Regards,
Bob
Thanks Bob. Nice article.
good grief…not only did they admit to the dust bowl….they admitted it was a lot warmer
“Unprecedented” they said. I guess that means the 1930’s temperatures had no precedent, even recent years like 2016 don’t measure up.
Hansen said that 1934 was 0.5C hotter than 1998, which makes 1934, 0.4C hotter than 2016, going by the UAH satellite chart. Unprecedented. 🙂
Agreed.
One query: has this article taken any account of the quality of observation?
Are the 1901-1960 thermometers, for example, as accurate as those in the 1986-2016 data?
Were the times of day of observations consistent?
Indeed, were the recording methods equivalent [1901 will, I think, probably have a different recording method to 2001 – but are they equivalent?
We have seen, through Anthony’s efforts, that not all surface stations are ideally configured in recent times [even though they may have been ‘good’ when first established].
If information could be found on these matters, it would boost the quality of the data presented, and the effect of that!
Auto
1901 to 1960, the thermometers were liquid in glass, that recorded the daily high and low. The high and low was then read with a standard mark one eyeball to the nearest degree, assuming the person doing the reading had been trained to place said eyeball on the exact same level as the reading in order to minimize parallax.
In recent decades, most sensors have been replaced with automated equipment that records the temperature hourly.
Because of these two difference, you really can’t compare modern temperatures to those taken a few decades ago.
Whether you take hourly or daily, the maximum + minimum by 2 is the average. 24 hours mean is not average.
sjreddy
Average of what?
The US is 2% of the planets surface.
Its just not very relevant for GLOBAL warming trends.
I would recommend reading the entire section for a clearer picture.
Climate Science Special Report: Temperature Changes in the United States
(https://science2017.globalchange.gov/chapter/6/?fbclid=IwAR0e8PX404eH51BZqP8GYZGRPXiiCUh_HqLVed0jTkMoihfwj-FWevo__5s)
The same report you are linking to said this about GLOBAL warming :
“Based on extensive evidence … “it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century,”**
For the warming over the last century,”
there is no convincing alternative explanation supported by the extent of the observational evidence**.”
Climate Science Special Report: Executive Summary
(https://science2017.globalchange.gov/chapter/executive-summary/)
The maximum and minimum temperatures though presented an increasing trend in India, the minimum trend is higher than the maximum trend. This clearly reflect the urban-heat-island effect on mimimum temperature. The average temperature showed around 0.5 oC raise. According to IPCC definition of global warming — thus it is less than 0.2 oC. If the network in rural areas increases, this may turn in to negative. From all the above presented graphs, it is clear that they follow the Inbndian pattern only.
Dr. S. Jeevananda Reddy
And also Dr Reddy, does the annual average global temperature taken from the average global daily temperatures (max+min divided by 2) throughout limited locations on the planet tell us anything about temperature itself? Does the average of very hot, very cold at a location not have more meaning than the average of the usual hot and cold even though the latter gives a higher average temperature for that location? Average telephone number in the phone directory, anyone? Might not be an actual telephone number.
A paper from the NWS in Tucson talking about UHI effect, population growth and reduction of record low temperatures –
https://www.weather.gov/media/wrh/online_publications/TAs/TA0810.pdf
Given that summer temps are pretty flat, and any average daily temp increase is due predominantly to increases of the low temp, I wonder how much of the increase in cold temps (less cold nights and winters) is due to UHI? It would tend to reduce how much things cool off during the night – or those longer, colder winter days.
…all of it
Rural stations show no increase
The benefit of computers is that it is really easy to access information. The downside is that it is really easy to change data.
I read 1984 at an early age. The idea that the powerful might seek to change history is, in the words of Ike, gravely to be regarded.
Given that we are living in the adjustocene, it is imperative that data be properly archived. Even the alarmists think so. link
The Internet can play a role of the Ministry of Truth. Google does so already. Search for [climate change blog], and you won’t find WUWT on the first page.
Quote: “And the winner, by a landslide:
1. RealClimate (790) — “Climate science from climate scientists.” The mother of all climate blogs. The posts and the comments are both “must reads.””
Search for any skeptical climate scientist and half of the links on the first page are to skeptical science, desmogblog, thinkprogress, etc.
https://www.therightinsight.org/Not-so-subtle-Influences-Search-Engine-Bias
I never use Google to search.
I use startpage.com
@Bob,
I will get kindle books purchased asap.
Great article.
Interesting. Thank you. Station data show that the overall observed warming trend is driven mostly by rising nighttime daily TMIN and not by daytime daily TMAX and the warming is seen mostly in winter months and not in summer. Please see
https://tambonthongchai.com/2018/04/05/agw-trends-in-daily-station-data/
I saw something about night time lows increasing at a faster rate than daytime highs.
https://www.nytimes.com/interactive/2018/07/11/climate/summer-nights-warming-faster-than-days-dangerous.html
Could it also a function of urban air temperatures not cooling off at night because of so much additional urban sprawl retaining more daytime heat around weather reporting stations that were once considered more naturally placed.
Applause, applause, for presenting us with some excellent observations (not simulations, heh), Bob Tisdale.
************************************
Re: night time temperatures
Mike Crow did some fine analysis of these in this article (https://wattsupwiththat.com/2013/05/17/an-analysis-of-night-time-cooling-based-on-ncdc-station-record-data/ ):
(quote from Crow’s article):
“Conclusion: The worldwide surface station measured, average, daily, rising temp and falling temps are: 17.465460F and 17.465673F for the period of 1950 to 2010.
Not only are the falling temperatures slightly larger than the rising temperatures, 17.4F is only 50%-70% of a typical clear sky temperature swing of 25F to 30F, which can be as large as +40F depending on location and humidity. …
Since recorded Min – Max temperatures show no sign of a loss of cooling on a daily basis since at least 1950, even if CO2 has increased the amount of DLR, something else (most likely variability of clouds) is controlling temperatures. This would seem to eliminate CO2 as the main cause of late 20th century warming.”
[added emphasis mine]
Where did I find this?….. (on page 1,755 of my handy dandy copy of “WUWT — The Battle for Science — The First 10 Years” 🙂 )
With the temperature inversions & wind speed define the reduction of outgoing radiation from the earth. When this is low, then night time temperatures rise. In rural areas this will not happen. The pollution and winter clouds help this process in urban areas.
Dr. S. Jeevananda Reddy
“…Alarmists Will NOT Like…”
They don’t have to. They will ignore, whitewash, and deflect.
Oh No! We are suffering an outbreak of milder weather! How perfectly dreadful!/sarc
What has this to do with the AGW liepothesis?
I thought it had been confirmed as a theodicy.
OK, Thanks for“Highlights of the Findings of the U.S. Global Change Research Program Climate Science Special Report” (boring). Now fold the tent and go do something worthwhile with my tax dollars.
The MSM and other news outlets must have miss that part. They have been saying “we are doomed if something isn’t done. Typical alarmism stuff.
Bob,
Why hide your light under a bushel ?, just send this to the GCRP and share their response with us.
Hi… I just tried to read this on the Facebook app on an iPad and got one of those dreaded pop-ups that have no way of closing that say “Congratulations…”
Annoying, but, from safari browser, no ad.
We’re half a century into the AGW hypothesis and all the data point to recurring natural weather phenomena yet the propaganda for a catastrophic climate upheaval persists. How anyone can believe there’s not more to this scam than scientific malfeasance is naive.
C02 has gone down in the USA since 1990 by about 20%. Is the report saying that there is no coloration between CO2 and their temps rising or have they discovered an inverse coloration? Maybe it is just in America that temps supposedly are going up and co2 goes down but you have to get rid of co2 to stop temps from going up?
I voted for Trump and have a BS degree in engineering so it must be me and my education level that makes me not get it.
Strangely enough….US CO2 emissions are back where they were in 1991
..CO2 levels were ~350ppm in 1991
Left up to the US CO2 levels would be back at 350ppm
US emissions have gone down by 20%. CO2 levels in the US, like levels in the rest of the world continue to rise.
“Will departing flight 1934 passenger James E. Hansen please pick up the white courtesy telephone?”
Unless I missed it I would like to see rural and urban temperatures separated. This report reads to me mixing UHI effect with rural to their preconceived outcome.
increased water vapor could make winter and night temps warmer and day max lower.
Humidity issues are studiously ignored by everyone in climate discussions. Most people don’t understand the notion of enthalpy and I’m starting to think that includes a lot of the scientists.
Yes, this is a very real issue, that and the assumption that all inward radiation must become outward radiation. There are hundreds of ways the earth can expend energy that doesn’t result in outgoing lw emr. Enthalpy is a biggie. As are endothermic chemical reactions, bio energy, conversion of heat to kinetic, and a bunch of other basic energy transformations. Without knowing the losses we can’t begin to estimate the energy balance.
Many people simply do not understand what a ‘mean’ is.
Primer 1: assuming no ‘spikes’, and assuming an even gradation
from min-to-max, if Day 1 max is 20 and min is 12, and Day
2 max is 19 and min is 14, then : Day 1 has the higher maximum
temperature, and Day 2 has the higher mean temperature.
If winters are less cold than before then there will be an increase
in the mean temperature:
If summers are ‘hotter’ than before then there will be n increase
in the mean temperature.
But these two situations are entirely different animals, and
all the Paris bumpf does not distinguish between the two.
From the article: “The decreases in the eastern half of Nation, particularly in the Great Plains, are mainly tied to the unprecedented summer heat of the 1930s Dust Bowl era”
Well, there you have it. The official government line is that the 1930’s heat was unprecedented. That means 2016, the so-called “Hottest Year Evah!” wasn’t really the hottest.
We haven’t been in a temperature uptrend. We have been in a temperature downtrend since the 1930’s. At least in the United States.
Who believes the US is unique in its historic temperature profile? One guy who does is James Hansen. He’s wrong. Alarmists would have us believe the the US temperature profile is somehow unique and while it shows temperatures declining from the 1930’s, the rest of the world follows the bogus Hockey Stick path and shows temperatures getting “hotter and hotter” from the 1930’s as time goes along.
Here’s an unmodified chart from Finland, which is halfway around the world from the U.S., yet its temperature chart looks very much like the U.S. surface temperature chart with the 1930’s showing to be as warm or warmer than subsequent years.
Other charts from around the world and from both hemispheres show this same temperature profile with the 1930’s being as warm or warmer than subsequent years. None of these unmodified charts resemble the bogus, bastardized Hockey Stick charts that are used to lie to the world and claim things are getting “hotter and hotter” when they are not.
The Hockey Stick chart is the only “evidence” the Alarmists have and all it is is a giant fraud. The 1930’s were hotter than today globally. The Alarmist cannot accept that because if they do it blows their CAGW scare story out of the water. We are cooling since the 1930’s, not warming. There is no crisis of temperature. There is no unprecedented heat today. That took place in the 1930’s.
As a meteorologist in the field now for 32yrs I’ve seen a lot of eye opening extremes in weather occur. If I no longer saw them I’d think something is wrong.
BTW getting wicked mobile phone redirects only from WUWT today while travelling.
I posted something … it disappeared into the ether
I have been saying this for years. GH gasses reduce extremes of temperature, because they also absorb some of the IR in incoming solar radiation (~55% of incoming solar radiation is in the IR) . Less radiation at the surface = lower Tmax.
Even if the average goes up, Tmin goes up a lot, but Tmax comes down a bit. GH gasses are good for the planet, even if the average warming is more than 2 degrees.
Thank you, Bob. The first thing scientists do when facing a problem, is to ask for more questions: when, where, how, why, who benefits from that … Then measuring and observing. This results in the hypothesis that can be tested and more questions.
We know already that global warming is not global and it is so mild that its is not warming for sure. Better meme for “climate change” is “stable weather”. I would call it “nice weather” if we take humans into account.
Winters are milder in the arctic. My Siberian willows (Salix schwerinii) will grow more and I have less need for heating 🙂
And the ice in Arctic is growing as usual. Despite a less cold weather this fall.
Snow on Greenland is a function of less cold weather.
http://www.dmi.dk/nyheder/arkiv/nyheder-2018/november/varm-luft-har-givet-mere-sne-til-groenlands-iskappe/
The map is in English!
Record breaking cooling in the last 2 years.
Someone other than climate skeptics noticed:
https://www.realclearmarkets.com/articles/2018/04/24/did_you_know_the_greatest_two-year_global_cooling_event_just_took_place_103243.html
And all these pretty, colorful maps are based off a shoddy, manipulated ‘data-set’ that is scientifically meaningless, at least to an honest scientist.
Exposure to the sky at the horizon has probably decreased at most locations due to tree growth and new buildings. When i look at old aerial views from the 1930s it is shocking how few trees there were then compared to now. Wouldn’t this in and of itself explain a little decrease in daily highs (sushine obscured a little bit more now in one spot morning and evening) and a larger increase in daily lows (the entire 360 degree sky view at horizon is now less, resulting in less IR lost to space and a higher nighttime temperature).
“When i look at old aerial views from the 1930s it is shocking how few trees there were then compared to now.”
Well the doomsdayers simply don’t report good news-
https://phe.rockefeller.edu/docs/Nature_Rebounds.pdf
They’re a depressive bunch of sad sacks.
If these are the trends using the whole Global Historical dataset, what do they look like using only well-sited stations, like the USCRN, that minimize the Urban Heat Island effect?
The graph fits in with my personal observation that here in the Southeast region things have been getting slightly cooler. No explanation for why that is happening, but we have had more ice and snow here the past few winters than in my entire life. They always blame global warming for that, too.
As a lay person I noted the graphing of temperatures maintained by HadCRUT4 when separated into those in the Northern Hemisphere and those in the Southern Hemisphere, the rate of increase is greater in the former. It seems to me that much of this would be attributable to the heat island effect given that there is significantly less land mass in the latter and there is more of modern urban civilization in the former. I would be interested in knowledgeable individuals comments.
The PDO and AMO basically give the majority of “global” temperature rise and fall. It all boils down to pressure zones kicking the ice out of the Arctic or not. There is no CO2 GH effect involved. I have yet to read a definitive answer as to what drives the PDO and AMO. It just “does”. Judith Curry has her “Stadium Wave” paper describing the sloshing effect on the Arctic ice.
Anybody notice that the MSM isn’t complaining anout the new head of the EPA anywhere near like it was with Scott Pruitt?
Think it’s time to put Pruitt back in as the head of the EPA…
Figure 6.3 pretty much matches this image:
Thank you, Bob
After reading your article, I went to the NCA4 and downloaded everything. I whent through NCA4 chapter by chapter, although I did not read every word. I then went to the Summary. I have questions about the chapters, but I expected that the summary would at least mirror what was in the chapters. The chapter 6 graphic in the summar is the one that Bob points out as being “the oddest graph in the report.”
Although I find NCA4 to be a series of cherry picked data to support the CAGW agenda, I feel that the summary is individually bits of cherry pits compbined with statements which are not supported by the NCA4 chapters.
The US is 2% of the planets surface.
Its just not very relevant for GLOBAL warming trends.
I would recommend reading the entire section for a clearer picture.
Climate Science Special Report: Temperature Changes in the United States
(https://science2017.globalchange.gov/chapter/6/?fbclid=IwAR0e8PX404eH51BZqP8GYZGRPXiiCUh_HqLVed0jTkMoihfwj-FWevo__5s)
The same report you are linking to said this about GLOBAL warming :
“Based on extensive evidence … “it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century,”**
For the warming over the last century,”
there is no convincing alternative explanation supported by the extent of the observational evidence**.”
Climate Science Special Report: Executive Summary
(https://science2017.globalchange.gov/chapter/executive-summary/)
UHI effects are produced not only by the higher heat-absorption of man-made materials, but also by a direct increase in the available thermal energy due to burning of fuel. The distinctive signature is a secular rise of nightly low temperatures, particularly in winter, when fuel consumption is highest. That’s precisely what the Special Report shows for the USA, where 20th century urbanization/industrialization was truly unprecedented. The third world is now catching up.