U.S. Heat Waves: Dessler Continues to Step In It

Atmospheric scientist Andrew Dessler of Texas A&M University created a stir online at Twitter last year when he decided that a graph published by the EPA, and cited by Bjorn Lomborg a year ago “just didn’t look right.”

Science doesn’t follow, “just didn’t look right” as a rule of discovery or investigation, and as a scientist, Dessler should know better. Following a personal viewpoint of “just doesn’t look right” is a fast track to confirmation bias. Here is what Dessler said:

But, like many climate alarmists, Dessler just has a hard time believing that any time in the past could be worse than the present when it comes to weather. There has been so much rhetoric about the age we live in as being “hottest ever” and “unprecedented” that some people actually begin to reject contrary data that has been around for years.

In this case, Dessler would have us believe that the “dust bowl” period in United States history is nothing compared to the ravages of heat waves and drought experienced in the United States today, and he set out to prove his beliefs with a series of Tweets which you can read here.

Recently, during a discussion with ClimateDepot’s Marc Marano, Dessler brought up the thread from last year again.

But what are the real facts about the 1930’s heat wave? Is it merely a statistical aberration or a “cherry pick” as Dessler suggests? Or is it real? And if it isn’t real, but “cherry picking” of data, as Dessler contends, why would the EPA publish it?

Research yields the following undisputable facts about the 1930’s heat waves, contradicting Dessler’s viewpoint. First, the World Meteorological Organization defines a heat wave as five or more consecutive days during which the daily maximum temperature surpasses the average maximum temperature by 5 °C (9 °F) or more.

1. Yes, extended heat and drought did actually occur through a majority of the United States during that period. The year 1936 was particularly bad. Wikipedia notes this:

July 1936, part of the “Dust Bowl,” produced one of the hottest summers on record across the country, especially across the Plains, Upper Midwest, and Great Lakes regions. Nationally, about 5,000 people died from the heat.


The U.S. National Weather Service says:

… the summer of 1936 featured the most widespread and destructive heat wave to occur in the Americas in centuries.


2. The heat waves of 1934 and 1936 were caused by natural ocean patterns, according to this peer-reviewed paper from 2015 which said,

Two ocean hot spots have been found to be the potential drivers of the hottest summers on record for the Central US in 1934 and 1936. The research may also help modern forecasters predict particularly hot summers over the central United States many months out.

Markus G. Donat, Andrew D. King, Jonathan T. Overpeck, Lisa V. Alexander, Imke Durre, David J. Karoly. Extraordinary heat during the 1930s US Dust Bowl and associated large-scale conditionsClimate Dynamics, 2015; DOI: 10.1007/s00382-015-2590-5

3. The Fourth U.S. National Climate Assessment (NCA) from 2017 did a detailed analysis of the United States heat waves, including cold and warm spells going back to 1900, and found the exact same thing the EPA did. Below is figure 6.4 from chapter 6. Note the very bottom panel.

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., and the heat wave intensity index is defined in Russo et al. Estimates are derived from long-term stations with minimal missing data in the Global Historical Climatology Network–Daily dataset. (Figure source: NOAA/NCEI).

The NCA added this, bold mine.

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. , Since the early 1980s (Figure 6.4), there is suggestive evidence of a slight increase in the intensity of heat waves nationwide as well as an increase in the concurrence of droughts and heat waves.


This 2017 NCA report clearly supports the EPA chart, and contradicts Dessler’s viewpoints of heat waves being worse in the present, and that the 1930’s heat wave spike was a result of some “cherry picking” of data.

4. An independent data analysis of heat wave events also contradicts Dessler.

The figure below is a result from 671 individual U.S. Historical Climatology Network (USHCN) stations with greater than 94 percent data availability.  This is the number of days in “heat waves” lasting at least 5 days in length, in which each day is above the 95th percentile of the distribution of the daily values per date.

There were 671 stations which qualified for the 94 percent available data of the total 1218 USHCN stations.

Note that the Western United States  (ID+OR+WA, CA+NV and AZ+CO+NM+UT) had their highest number of Heat Wave Days in the last decade, but the rest of the country was near/below the national average.  Clearly there have been some regional changes in the last 110 years, suggesting weather pattern changes, but for the nation as a whole (gray bars), the decade of 1932-1941 still stands out as the warmest.

Interestingly, this is a very different result compared to Dessler’s claims, especially when it comes to some of the graphs he posted, such as this one in his Twitter thread:

Dessler’s graph indicates the dataset he is using (Berkeley Earth) has had some temperature adjustments applied. The difference is not geographic as the result from the USHCN stations is weighted by area also. We can get Dessler’s result, more or less, if we add 1°F to each daily temperature from 1980 to 2005 and then 2°F more from there to the end of the data.  This gives a rough estimate of the magnitude of the adjustments that have been applied to the dataset he used.  

The bottom line: unless you use adjusted data, you can’t get to Dessler’s results.

If Dessler wants to claim that the hundreds of observers that made high temperature measurements over decades should have that hard-earned data adjusted, he can claim that, but he ends up with a result he claims to abhor, one that is “cherry picked” by using adjusted data rather than the actual high temperatures that were recorded through history. Adjusted high temperature data is not the same as actual measured high temperatures, it isn’t even real.

Imagine if your evening news weather report, when reporting high temperatures for your area that day, used adjusted high temperature data to present the results to viewers. The backlash would be swift and vicious.

You can compare all of the facts in points 1-4 above to Dessler’s “just didn’t look right” analysis and make your own judgments about when heat waves were worse in the United States. You can believe the real actual data measured at the time, or the data that has but put through a statistical adjustment mill decades later.

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Tom Halla
June 28, 2022 2:07 pm

Why do “adjustments” if one cannot demagogue them?

Reply to  Tom Halla
June 28, 2022 2:39 pm

No need to change definitions, just change the data.

June 28, 2022 2:11 pm

Dessler the data botherer

Reply to  Phil Salmon
June 28, 2022 2:59 pm


MarkW, your comment was removed because it was a beyond the pale comparison. Don’t do it again, or you WILL BE BANNED.

For right now, you are in moderation – Anthony

Last edited 1 month ago by Anthony Watts
June 28, 2022 2:16 pm

I listened to Dressler on Josh Rogan a couple of months ago. All I could think was God, please give me 15 minutes to cross examine this clown. (I’m an ex criminal defense counsel).Dressler is an idiot – his comment about it not looking right would get him destroyed on the stand.

Jeff Alberts
Reply to  Terry
June 28, 2022 8:36 pm

Maybe you listened to Dessler on Joe Rogan?

john harmsworth
June 28, 2022 2:20 pm

The flip side of this is that he nods approvingly at any old garbage, so long as it :looks right”. By which he means, shows a sufficiently scary amount of warming. “Sufficiently scary” being defines as , worse than the last thing he looked at.

Last edited 1 month ago by john harmsworth
Joe Gordon
June 28, 2022 2:20 pm

The Dessler Effect: the perception of past temperature decreases in inverse proportion to the observer’s demonstrated religious activity.

Rud Istvan
June 28, 2022 2:27 pm

Dessler published a positive cloud feedback paper in 2010 that used a comparison of CERES clear sky to all sky. The only problem was that his regression analysis had an r^2 of 0.02–meaningless. And he didn’t notice that ‘that doesn’t feel right’.

He probably also thinks Steinbeck’s novel Grapes of Wrath about the dust bowl years is just a work of pure fiction based on a fevered imagination.

Nicely done, AW. Ridicule is the best response.

Reply to  Rud Istvan
June 28, 2022 4:20 pm

I think I likened the graph to an ink blot! or to the result of someone sneezing!

Reply to  Rud Istvan
June 29, 2022 3:30 am

He probably also thinks Steinbeck’s novel Grapes of Wrath about the dust bowl years is just a work of pure fiction based on a fevered imagination.”

No, that was “Travels With Charley”


Trying to Play Nice
Reply to  JoeF
June 29, 2022 6:23 am

Well, I guess a guy who wasn’t there knows much more than the guy who was.

Reply to  Trying to Play Nice
June 29, 2022 3:54 pm

That’s how the 1/6 Kangaroo Court rolls.

June 28, 2022 2:33 pm

Dessert just doesn’t look right!!!

Reply to  Lance
June 28, 2022 2:34 pm

Damn spell corrector


June 28, 2022 2:41 pm

Does Dessler’s gridded data include the oceans? Those are ridiculously filled in, and can’t be trusted prior to 1979.

Judging by his graph, he’s using Python. I bet the poor fool doesn’t do the proper math for oblate spheroid Earth:


Probably thinks the Earth is a ball.

Matt Kiro
Reply to  Zoe Phin
June 28, 2022 3:15 pm

His graph is just for the continental United States. But just head to Tony Heller’s site to see how daily maximum temps have been decreasing for 90 years

Reply to  Matt Kiro
June 28, 2022 3:29 pm

Thanks, but he’s still wrong counting every grid cell the same despite their area differences.

Last edited 1 month ago by Zoe Phin
Reply to  Zoe Phin
June 30, 2022 7:55 am

Dessler says he’s using Berkeley Earth’s gridded data set, which provides data both as an equal-area grid or on a lat-long grid that weights grid cells according to size. In either case he is not oversampling any of the grid cells in his analysis.

Last edited 1 month ago by AlanJ
June 28, 2022 2:48 pm

Did Dessler check with the EPA? The graph is on their website.

comment image

This figure shows the annual values of the U.S. Heat Wave Index from 1895 to 2020. These data cover the contiguous 48 states. An index value of 0.2 (for example) could mean that 20 percent of the country experienced one heat wave, 10 percent of the country experienced two heat waves, or some other combination of frequency and area resulted in this value.

Data source: Kunkel, 20219

Web update: April 2021


Reply to  David Middleton
June 28, 2022 8:19 pm

Oh… how awkward.

Sweet Old Bob
Reply to  David Middleton
June 29, 2022 9:46 am

AD has ADD ?


Reply to  David Middleton
June 29, 2022 10:22 am

The graph is on their website.

What’s sad is how many people responding to him don’t (want to) realize that.

June 28, 2022 2:50 pm

If the data doesn’t match what you are hearing in the media, maybe you should question what you are hearing in the media, rather than the data.

Reply to  MarkW
June 28, 2022 3:01 pm

Nah. We don’t want their fragile little heads to explode, discovering that their religious convictions aren’t actually supported by evidence. Or do we…?

Reply to  stinkerp
June 28, 2022 8:25 pm

‘Splodey heads?!? What’s not to like?

Clears my sinuses every time. Works wonders. XR oughta try it instead of sitting in the middle of the road.

Believe in The Science®.

June 28, 2022 2:53 pm

Let’s take Berkley Earth’s gridded daily maximum

There’s your problem right there.

Reply to  MarkW
June 28, 2022 6:17 pm

Exactly. Berzerkly produces homogenized Bull Crap based on an unsubstantiated claim that several hundred observers from the time could not read a thermometer correctly or the time of observation was all wrong.

Twenty four states set their record high temperatures during the 30’s.

Record Highest Temperatures by State (infoplease.com)

But according Berzerkly that’s all wrong.

And so is this.

comment image

Dessler already made his incompetence evident when he declared a “permanent drought” for the SW and then the next year Texas had flooding rains so choosing to use BEST instead of actual field data is to be expected.

Jim Gorman
Reply to  rah
June 29, 2022 4:27 am

Berkley needs to quote the variance in their initial daily temps. Variance should be carried through the whole process, not just posted with the variance in the last quoted average. Every average that is taken reduces the variance. This isn’t scientific, it is akin to p-hacking, i.e., finding the statistical analysis that best gives the answer that you are after.

Reply to  MarkW
June 28, 2022 6:19 pm

This ^

Who was that Bitcoin miner who wanted everyone to be contracted traced during Covid? He was a big Berkeley guy.

JC Penny
June 28, 2022 2:59 pm

A couple years ago I heard the term, “a little bit unprecedented” referencing Spring storms in Louisianna occurring at the same time the Mississippi was at flood stage from Spring melt. Maybe that was code for, “after we changed the data a little bit it was a record.” Looks right to me.

Clyde Spencer
Reply to  JC Penny
June 28, 2022 7:04 pm

That is similar to being “slightly pregnant.”

Chris Hanley
June 28, 2022 3:06 pm

Adjusted high temperature data is not the same as actual measured high temperatures, it isn’t even real.

Reminiscent of the email from Tom Wigley to Phil Jones exposed by ‘ClimateGate’:
Here are some speculations on correcting SSTs to partly explain the 1940s warming blip … If you look at the attached plot you will see that the land also shows the 1940s blip (as I’m sure you know) … So, if we could reduce the ocean blip by, say, 0.15 degC, then this would be significant for the global mean — but we’d still have to explain the land blip.It would be good to remove at least part of the 1940s blip, but we are still left with “why the blip”‘.
When does adjusted data cease to be ‘data’?
Data is defined as ‘facts and statistics collected’ (Oxford) so the term ‘adjusted data’ is oxymoronic IMO.

Reply to  Chris Hanley
June 28, 2022 6:28 pm

I should have read your comment before my post. yours’s is much more elegant!

AGW is Not Science
Reply to  Chris Hanley
June 29, 2022 9:51 am

What they call “data” is no longer data. It’s guesswork as to what they THINK the temperature ‘would have’ been ‘but for’ any number of excuses used to make it seem like a better match to rising CO2 levels.

Data is the instrument measurements. Anything else is garbage.

June 28, 2022 3:13 pm

Dessler is the ultimate politician-scientist as he showed clearly in his Joe Rogan interview.

H. D. Hoese
June 28, 2022 3:21 pm

I was in college at College Station during the 50s drought, broken in spring 1957, an exceptionally very wet year. He may be fixated by the 2010-11 exceptionally dry period. [Nielsen-Gammon, J. W. 2012. The 2011 Texas Drought. Texas Water Journal. 3(1):59–95. https://doi.org/10.21423/twj.v3i1.6463%5D The 50s drought was worse in Texas than the 30s, irrigation from the 30s drought helped, wetter and other conditions since continues to help. He doesn’t know that he is a prime example of the lack of homework going on in too many fields. He needs to read my paper.

Hoese, H. D. 1960. Biotic changes in a bay associated with the end of a drought. Limnology and Oceanography. 5(3):326-336. https://doi.org/10.4319/lo.1960.5.3.0326     
Open Access. First line.–“Heavy rainfall in early 1957 broke the most severe drought in the history of Texas.” Still true, check out the cattle deaths.

Tim Gorman
Reply to  H. D. Hoese
June 28, 2022 3:34 pm

For far too many scientists today believe history began the day they were born. Thus no need to ask why prairie grass on the High Plains evolved to have root systems that go down 8′ to 10′ or even deeper. The High Plains haven’t been a semi-arid desert while they have been on the earth so it must have never been a semi-arid desert – at least until today!

Reply to  Tim Gorman
June 29, 2022 10:47 am

For far too many scientists today believe history began the day they were born.

Not just scientists, and often not even that far back…

Reply to  H. D. Hoese
June 28, 2022 3:38 pm

Live in College Station myself but don’t work at university. Andy Dessler lives just down the street from me.

Reply to  Stevek
June 28, 2022 9:36 pm

Oooooo… negative thoughts… bad H.R. Baaaad H.R.

Per Bart Simpson:

“I didn’t do it! Nobody saw me do it. You can’t prove I did it.”

Reply to  H. D. Hoese
June 28, 2022 5:45 pm

The Last Picture Show drought! I have a cool graphic for this… Hopefully I can find it.

Reply to  David Middleton
June 28, 2022 6:36 pm

Back in 2018, the other fathead, Mikey Mann wrote this article…

Climate change was behind this summer’s extreme weather

In the article he blathered about the 2011 Texas drought (as did the other fathead, Dessler)….

Our study shows that climate change is making that behavior more common, giving us the disastrous European heat wave of 2003 (during which more than 30,000 people perished), the devastating 2011 Texas drought (during which ranchers ranchers in Oklahoma and Texas lost 24 percent and 17 percent of their cattle, respectively), the 2016 Alberta wildfire (the costliest natural disaster in Canadian history) and, yes, the extreme summer of 2018.

Obviously, neither fathead is acquainted with the great Texas historian, Larry McMurtry.

[T]he devastating 2011 Texas drought (during which ranchers ranchers in Oklahoma and Texas lost 24 percent and 17 percent of their cattle, respectively)…

I have lived in Texas since 1981. The 2011-2012 drought was really bad… Almost as bad as The Last Picture Show drought. Here in Texas, rather than destroying our economy just in case droughts get worse in the future, we build dams and expand water infrastructure.

comment image
Texas responded to The Last Picture Show drought by building dams, lots of dams.  Water For Texas

Texas responded to the Manntastic Drought in much the same manner, by building more water infrastructure, including 26 new major surface reservoirs…

In the 2012 State Water Plan, 26 new major reservoirs are recommended to meet water needs in several regions (Figure 7.1). A major reservoir is defined as one having 5,000 or more acre-feet of conservation storage. These new reservoirs would produce 1.5 million acre-feet per year in 2060 if all are built, representing 16.7 percent of the total volume of all recommended strategies for 2060 combined (Figure 7.2). Not surprisingly, the majority of these projects would be located east of the Interstate Highway-35 corridor where rainfall and resulting runoff are more plentiful than in the western portion of the state.


Last edited 1 month ago by David Middleton
Reply to  David Middleton
June 29, 2022 2:57 pm

Texas, like the country of Australia, are lands of extremes and have been as long as records of their weather/climate have been written.

David Dibbell
June 28, 2022 3:28 pm

Even NOAA’s own adjusted data for monthly average Tmax for the contiguous U.S. shows Dessler’s sense of what doesn’t look right is poorly trained. This is not “heat waves” per se but you can see why the EPA graph makes sense.

June 1895-2021

July 1895-2021

August 1895-2021

June 28, 2022 3:32 pm

Wouldn’t he also have to adjust the crop yields, rainfall, farm closures etc

Tim Gorman
Reply to  Stevek
June 28, 2022 3:37 pm

Yes. And just like the recent past where we have been having global record grain harvests for the past twenty years they still believe climate change is killing the global grain harvests. It’s called either ignorance or cognitive dissonance, take your pick.

Michael in Dublin
June 28, 2022 3:39 pm

Did Dessler take his dog for a walk on one of these extremely hot days and forget his pooper scooper and accidentally step in it? If he can let his imagination run riot so can I.

June 28, 2022 4:17 pm

People like Dessler have got away with their dishonesty for years thinking that the public will never take action. Well, the public mood is getting angry and they may well regret their arrogance.

June 28, 2022 4:33 pm

When I read about people like Dressler saying that we are experiencing more heatwaves now as compared to the 1930s, I’m reminded of each state’s high temperature record. The highest number of state high temperature records are still from the 1930s, disqualifying Dressler as a credible scientist.

June 28, 2022 5:52 pm

Actually, “doesn’t look right” as a prompt to dig deeper and question your analysis and conclusions is to be commended. I have trained numerous graduates and pointed out to them that if we just wanted people to pull numbers out of models, we’d hire people off the street, not university-trained engineers. The value they add is in reviewing their own work, identifying their mistakes, fixing them, and learning from them. The backstop was my review, and I’d apply a “does it look right” filter as the first step of the review process.

However – manipulating data to fit your bias is completely different, as is torturing it to do the same.

June 28, 2022 5:58 pm

It is not enough to look at summertime high temperatures. What were the corresponding summertime nightly lows. And what were the wintertime highs and lows at the same years?

Whether one considers the “dust bowl” era to be warmer than today or not, daily highs in just one season do not define climate.

Generally speaking, the hottest places on Earth are also very dry, low elevation places. High humidity tends to reduce daytime highs and increase nighttime lows. In dry deserts the daily temperature spreads in summer are far greater than the temperature spreads in humid areas. In places like Florida the summertime daily spreads average only 15-20 degrees, whereas in desert areas the daily temperature spreads can be 50+ degrees in the summer.

The “dust bowl” era in 1930s America was not just hot in the summer, it was also very dry all year long, and very windy too. Those weather related factors combined with a lack of soil conservation practices, and over cultivation of non-irrigated dry land crop production produced the extreme dust storms and severe erosion of the so-called “dust bowl” era.

Robert B
Reply to  Duane
June 28, 2022 7:38 pm

The issue might be using minimum temperatures to show the US is warming, then blame a hot and dry day on global warming – or worse, the wildfire lit by an idiot.

Tim Gorman
Reply to  Duane
June 29, 2022 4:37 am

Climate is defined by the entire temperature profile. That’s why using mid-range values to describe “climate” is so misleading. All kinds of temperature ranges can have the same mid-range value. This follows right on through to using the mid-range values to calculate a Global Average Temperature.

Mike Maguire
June 28, 2022 6:07 pm

Let’s look at the Record hottest temperatures ever recorded for every state in the United States.
24 of the 50 states had their hottest temperature ever in the 1930’s. Almost as many as all the other decades combined.

How many states had their hottest temperature ever since 2000, a period more than twice as long as the 1930’s and during the supposedly hottest 2 decades of US history. Just 6 states.



It’s awesome when the data speaks louder than the bullshit!

Recent warming in the US has warmed low temperatures much more than high temperatures!

Screenshot 2022-06-28 at 19-52-31 Newly found weather records show 1930
Mike Maguire
Reply to  Mike Maguire
June 28, 2022 6:24 pm

100+ degree days at one site in southwest Iowa.

comment image

Iowa 100 degree days.png
Mike Maguire
Reply to  Mike Maguire
June 28, 2022 6:30 pm

comment image

Link for that last graph

June 28, 2022 6:24 pm

One you adjust data it no longer data. It is what you think the data should be and that is not data.

Clyde Spencer
Reply to  mal
June 28, 2022 7:15 pm

It is tart cherry pie.

Jim Gorman
Reply to  mal
June 29, 2022 5:03 am

It is fiction. Each and every creation of new information should be documented with the calculation used and why.

I agree with AW’s view that every replacement of data with newly created information denigrates the dedicated people who read and recorded temperatures. What you end up with is a mashed banana of what the “scientist” thinks temperatures SHOULD HAVE BEEN!

AGW is Not Science
Reply to  Jim Gorman
June 29, 2022 10:01 am

What you end up with is a mashed banana of what the “scientist” activist-posing-as-scientist thinks temperatures SHOULD HAVE BEEN!

Fixed it for you. Once these so-called “scientists” lose their objectivity, they are no longer worthy of the title “scientist.”

Gary Pearse
June 28, 2022 7:32 pm

“the summer of 1936 featured the most widespread and destructive heat wave to occur in the Americas in centuries.”

Add to this Canada, Europe Greenland, South Africa, Paraguay, Ecuador … which supports the idea that 30s to mid 1940s was actually the hottest period globally since the Medieval Warm Period. Even Jim Hansen expressed disappointment that Super el Niño 1998 did not set a new record. This is what set him on his pre-retirement quest to change that.

The 1936 record stood until 2007 when Hansen fiddled the record to make 1998 the hottest.

BTW, here is Capetown, South Africa’s Temperature record before it was “homogenized” following Hansen.

comment image?w=816&h=567

Indistinguishable from the US pre-homogenized! And look at what the changes did to Capetown:

comment image?w=791&h=464

June 28, 2022 7:35 pm

“Heat waves (6-day periods…)
““heat waves” lasting at least 5 days in length”

Robert B
June 28, 2022 7:43 pm

“It don’t look right” has a place in science, as in it’s different to my back of envelope calculations. In this case, the equivalent is that the Dust Bowl era suggests more extreme heat occurred in the 30s even if just because it was very dry over a vast area. That it’s an inconvenient fact should not trigger the same gut feeling.

June 28, 2022 11:33 pm

Many discoveries come from “that’s odd” or “that doesn’t look right” moments, but the point is that after that moment and before the discovery there’s a typically intense period of research. This guy seems to think he can miss out the middle step.

AGW is Not Science
Reply to  Mike Jonas
June 29, 2022 10:08 am

It’s one thing to apply a “that doesn’t look right” thought process to something you have personally produced, or which you can reproduce (as in an experiment).

Applying it to historical temperature records is pseudo-scientific malfeasance. The recorded instrument readings are “DATA.” Anything that alters that is no longer “DATA” at all.

Geoff Sherrington
June 29, 2022 1:42 am

For Australia, I have used both raw and ACORN-SAT adjusted daily maximum temperatures to analyse heatwaves in the 6 State capitals that host many of the longest historic T records as well as about 70% of our people now. Some measurements go back to the 1860s.
There are many definitions of heatwave. I simply calculate for each year the average Tmax temperature of all consecutive days for lengths of 1, 3, 5 and 10 days. The hottest each year go into a draw for Top 40 to make it simpler to see what is happening. Against my better judgement, I have inserted linear least squares regression trend lines to save wear on eyeballs doing much the same, as is common prectice.
What can be said? This is not a continent-wide survey. To do that requires data I do not have. It uses a simple definition of heatwave that does not involve, for example, Tmin or humidity.I insert a few dummy temperatures for missing data, then check that they probably make no difference to anything except ease of computong.
Apoart from those confessiions, the data seem to indicate a high sensitivity to cherry picking, rather like Kip Hansen finds for sea level changes. You can make assertions about these heatwaves that more or less contradict each other depending on how you cherry pick. Unlike USA, we did not seem to have dustbowl conditions at these locations in the 1930s.
The finding that interests me most is the temperature of the heatwaves. Taking raw data and 5-day waves, the usual temperatures of the Top 40 heatwaves are in degrees C:
Brisbane 34.8
Sydney 33.3
Melbourne 37.5
Hobart 30.2

The long-term average of all daily Tmax is:
Brisbane 25.4
Sydney 22.1
Melbourne 19.9
Hobart 17.0

The latitudes of these places is
Brisbane 27 degrees south
Sydney 32
Melbourne 37
Hobart 42

These 4 cities ate 350 miles apart down the east coast, getting further from the Equator and showing this in their ordinary daiuly average Tmax. But the average for the Top 40 heatwaves does not follow this simple decline as you move away from the Equator. Melbourne heatwave temperatures average 3 degrees C more than Brisbane. Part of the rhe reason is that the hottest, longest heatwaves develop many miles away from these cities, as in desert around Alice Springs (roughly). As they move to Melbourne, the temperature cools, with faster air mass movement giving hotter, shorter heatwaves in Melbourne aand slower air movement giving longer, less hot heatwaves to melbourne.

You readers ahould all be doing thius simple type of analysis for your own regions. The data are open to the public, the computing is dead easy. Here are 96 graphs to enage your analytical minds. Please tell us what you deduce from all this.

Geoff S

Robert B
Reply to  Geoff Sherrington
June 29, 2022 4:08 pm

Any heatwave index that counts number of readings above a cutoff is just going to amplify half a degree higher readings on average, probably the result of a change of equipment in Australia or heat island effects. Good to see that you avoided that.

If you are going to do that to show that heatwaves are becoming more common rather than a bit hotter, you would detrend the data first or have cutoffs that increase with time. That this is ignored suggests that it’s deliberately propaganda.

Geoff Sherrington
Reply to  Robert B
June 29, 2022 4:47 pm

Thanks for your input. I am happy to send you the raw digital data if you want to improve on what I showed. Are you able to calculate for your own region to extend this type of analysis?
The BOM were well aware of UHI when making the adjustments I show. Australia has no significant Time of Observation bias, US does. I stand by my method. There is some circularity in detrending T data sets by adjusting some T that cause the trend; you would need a method to remove the unwanted UHI trend without data to do it.
I do not do propaganda, I merely criticise others who do. Geoff S

Robert B
Reply to  Geoff Sherrington
June 29, 2022 7:03 pm

The detrending is to avoid coming to the conclusion of more frequent heatwaves because the same weather pattern gives 0.2°C above the 90 percentile instead of 0.2°below, for example, if there has been a half degree increase in average maximum temperatures. You are not going to sense half a degree hotter but being told that the number of extreme days has gone up 10% sounds very much distressing. Still a half-adze job but good enough to nullify propaganda.

June 29, 2022 2:35 am

State high temperature records are still heavily dominated by the 1930’s.

Geoff Sherrington
Reply to  Tom.1
June 29, 2022 3:22 am

If that is a comment about Australia, here are some old Sydney and Melbourne graphs of hot days that do not show a 1930s blip. There are possibly locations in central and north Australia which have them, but I cannot recall any so they might not stand out so much. Geoff S

Reply to  Geoff Sherrington
June 29, 2022 5:59 am
Bruce Cobb
June 29, 2022 4:20 am

That “feeling” Dessler had is called cognitive dissonance. It’s when your belief system smacks head on into reality.

Barnes Moore
June 29, 2022 4:51 am

Dessler, like Mann, is nothing more than an activist with a PhD who calls himself a scientist. They use models to manipulate data to achieve a predetermined desired outcome and call it science.

Jeff Reppun
June 29, 2022 7:16 am

According to NOAA records, 24 of our US states set their current all time high temperature records in the summers of 1930 thru 1936. About half of the remaining states set their current records prior to 1930.

June 29, 2022 9:34 am

I don’t think the difference in his result is due to adjustments. The other datasets are also adjusted. He just picked a completely different measurement. The number of “hot” days in a year at every grid cell. Who knows how many different measurements he tried before he found one that looked right.

Geoff Sherrington
Reply to  Nicolas Nierenberg
June 29, 2022 4:13 pm

Have a look at the graphs I posted. Half are adjusted, half are not. I do not know which are closer to actual, correct. Geoff S

Scott J Simmons
Reply to  Nicolas Nierenberg
July 12, 2022 10:11 am

You’re absolutely right this has nothing to do with adjustments. The reason for the differences between Dessler’s and Kunkel’s metrics is largely due to the fact that Dessler’s metric isn’t arbitrary. It actually plots how heatwaves have increased in gridded data. Kunkel’s metric considers only 876 thermometers without any area weighting. If those 876 thermometers represented the entire US, I suppose this would be fine, but but Dessler showed that they don’t.

June 29, 2022 10:45 pm

Dessler publicly stated that if observations differed from model output the observations must be wrong.

July 2, 2022 6:16 am

Ah climate science… When the raw data doesn’t support the “consensus” make adjustments to the data.

Scott J Simmons
July 12, 2022 6:30 am

Kunkel’s metric, which is on the EPA’s website and in the NCA4 report, is based on 876 thermometers. What Dessler showed is that those thermometers do not represent the US accurately. Kunkel’s metric is arbitrary, and arbitrary metrics yield arbitrary results. If you use gridded data, heat waves have been worse in recent decades than they were in the 1930s. And as his graphs show, it’s false to claim that “Dessler would have us believe that the ‘dust bowl’ period in United States history is nothing compared to the ravages of heat waves and drought experienced in the United States today.” In point of fact, his graphs show that the 1930s heatwaves were pretty bad. They’re just worse now.

I summarized Dessler’s actual argument and analysis here: https://woodromances.blogspot.com/2022/02/were-1930s-dust-bowl-heatwaves-worse.html

Last edited 1 month ago by Scott J Simmons
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