From Dr Roy Spencer’s Global Warming Blog
by Roy W. Spencer, Ph. D.

Fig. 1. “Study of Cirrus Clouds”, painting by John Constable, circa 1822. Cirrus as a cloud type was first defined by Luke Howard in 1802.
2025 isn’t just the current year, or a Heritage Foundation project of conservative principles for political action for the new Republican President. In the 1990s it was also the result of an Air Force directive to “examine the concepts, capabilities, and technologies the United States will require to remain the dominant air and space force in the future“.
As a partial response to that directive, several students at the Air War College in 1996 produced a document, largely theoretical in content, entitled Weather As a Force Multiplier: Owning the Weather in 2025. That document, which was declassified in 1998, seems to have provided sufficient evidence some people needed to claim that our government has been secretly modifying the weather, altering the atmosphere, poisoning us with chemicals, or whatever else you can think of.
Now, as a general rule, I’m not against conspiracy theories. For example, it has become clear that experts knew early on that the COVID-19 virus likely did indeed come from a lab leak in Wuhan, China, and one might reasonably conclude there was a conspiracy to hide such evidence. Even the New York Times says we were misled. Conspiracies exist.
But not everything we see in the world that we perceive as a threat is the result of a conspiracy, and some people are just easily triggered by what they see. Many years ago I attended a local town hall meeting where a congressional candidate was speaking. During the Q&A period, an appropriately-attired biker dude got up and wanted to know what the candidate was going to do about all of the “chemtrails” the biker saw in the skies above him as he traveled around the country. The candidate provided a an appropriately vague and soothing response.
So, how did this “chemtrail” theory arise?
It seems to be a combination of peoples’ misunderstanding of the clouds they see in the sky combined with increasing distrust in our government, fueled by the 2025 Air Force study alluded to above. It also seems to be exacerbated by lesser standards of math and science education in recent decades, leading to a new generation of adults who can not critically examine claims made by others.
Contrail Production by Jet Aircraft is Well Understood
For those of us who know meteorology, those visible cloud streaks left behind travelling jets are “contrails” (condensation trails), produced during the combustion of jet fuel. The chemistry of jet fuel combustion is well understood, which includes the by-products of that combustion. During combustion, 1 kg of jet fuel produces about 1.3 kg of water (hydrogen in the fuel combines with oxygen from the atmosphere to produce H2O, water). That water exits the jet engine as water vapor in such high concentrations at extremely cold temperatures (around generally -30 to -50 deg. F) that there is much more water than the atmosphere can hold without condensation (cloud formation) occurring.
As a result, trails of cirrus clouds (contrails) are produced. Depending upon the relative humidity (RH) of the surrounding environmental air, those contrails can either rapidly evaporate (if RH is very low), leaving essentially no visible evidence, or can persist and even expand in coverage for many hours if the RH is high. In a high RH environment, jet-produced cirrus can actually scavenge water vapor from the surrounding atmosphere, causing continued growth of the contrails.
Fig. 2. Four-engine contrails produced by jet aircraft. Different illumination situations can change the contrail appearance, just as is the case with natural cirrus clouds (source).
The presence of wind shear (changing wind direction or speed with height) can cause distortion of the resulting clouds into myriad shapes. Often, the resulting jet-produced cirrus clouds are not easily distinguishable from natural cirrus clouds produced by weather systems; other times they are easily distinguishable. Literally as I was writing this, I took a picture out my office window showing both natural and jet-produced cirrus clouds.

Fig. 3. Natural and jet-produced cirrus clouds at sunrise, Huntsville, Alabama, 19 March 2025.
But when, and why, did the “chemtrail” conspiracy theory theory gain traction? And why does it persist today? The theory posits that the visual trails of condensed water vapor seen behind jet aircraft operating at high altitudes in reality represent the spraying of chemicals for some nefarious purpose(s). I routinely see comments on X and Facebook from people alarmed at the “chemtrails” they see. Those evil purposes of chemtrail production range from geoengineering (purposely changing the climate) to mind control and the spread of sickness that can be treated by pharmaceutical companies to increase their profits. Many weather experts have tried to debunk these ideas, for example Cliff Mass, professor of atmospheric science at the University of Washington.
Weather as a Force Multiplier: Owning the Weather in 2025
So, does the U.S. Air Force now own the weather in 2025, as predicted in the 1996 report? Of course not. Most of the theoretically possible technologies in that report for either clearing clouds, or creating clouds, in the battlefield did not exist in the 1990s. The report is full of pie-in-the-sky concepts, including cloud seeding to produce precipitation (the subject of much civilian research in recent decades), but admits “artificial weather technologies do not currently exist. But as they are developed, the importance of their potential applications rises rapidly.”
Yes, there have been experiments (mainly civilian) extending back to the 1950s involving seeding clouds to get them to precipitate. This involved dropping a chemical, such as dry ice or silver iodide crystals, to help convert super-cooled water droplets into precipitation. Project Stormfury, started in the 1960s, researched seeding hurricanes in the periphery to reduce the intensity of the central part of the cyclone, which is where most of the damaging winds and storm surge occur. But the idea was abandoned when it was realized hurricanes already convert almost all of the condensed cloud into precipitation anyway, without any help from humans.
This isn’t to say that it is impossible to seed clouds and produce precipitation, at least on a very localized basis in specific weather situations. But the research results have been mixed, and generally speaking, unless a cloud is getting ready to precipitate anyway, seeding doesn’t do much to the cloud, except make it precipitate sooner rather than later. People have a greatly exaggerated perception of what humans can do to purposely impact weather processes.
Now, I’m not privy to any weather modification technologies that DoD might have in the works. But after nearly a half-century of working in weather and climate, I can tell you there is little we can do to affect weather, either intentionally or unintentionally.
Let’s examine the AF report example of creating or clearing clouds in the battlefield. Imagine a wartime situation where the AF wants to clear a cloud (or fog) to allow precision visual identification of a target for bombing. Theoretically, this could be done with a powerful microwave directed-beam energy source (maybe from a special aircraft flying just ahead of a missile-carrying aircraft) to temporarily evaporate the cloud water. To give some idea of the energy that would be required to do that, we can compute how much energy is required to evaporate a path of fog having dimensions of 100x100x100 meters having a liquid water content of 0.1 grams water per kg of air. Assuming maybe 25% or so of the directed microwave beam energy will go into heating air and evaporating the liquid water, one can estimate the energy required of such a directed-beam device would be around 1 billion Watts (1 billion Joules of energy produced for 1 second). This is indeed in the realm of the estimated power output of DoD directed beam energy sources, at least from the ground. I have no idea whether such a large energy source could be produced by an aircraft.
But, even if the Air Force could, would they even want to? I’m pretty sure smart weapons now exist which have passive microwave technology allowing a target to be seen through relatively modest cloud cover.
So, What About Chemtrails? And Geoengineering?
As far as I can tell, the AF report cited above does not mention technologies that would disperse chemicals through jet exhaust (or other aircraft orifices). Besides, if such chemtrails exist, they are spreading their “chemicals” over everyone, including the families of the people conspiring to cause chemtrails.
Why would anyone do that?
Isolated photos do exist of jets dumping fuel, which comes out of different special wing ports, away from the engines. Sometimes this is cited as evidence of chemicals being spread for nefarious purposes. But this “fuel jettisoning” is a rare occurrence, usually in emergency situations, and is estimated to occur less than once per 100,000 commercial flights.
But there has been lots of research into whether jet contrails inadvertently affect climate, which would be a case of accidental geoengineering. Contrails reduce the amount of sunlight reaching the surface (a cooling effect), but that is more than offset by their reduction in the infrared (IR) cooling of the climate system, leading to a net heating. The best estimates are that global jet traffic produces less than 0.1 Watt per sq. meter of net radiative heating of the climate system, which is in the noise level (by comparison, natural solar heating and infrared cooling of the global-average climate system is ~240 Watts per sq. meter). Locally, where there is lots of air traffic, that value goes up to possibly 0.5 Watts per sq. meter, which is probably still not detectable in the presence of natural variations in temperature. An early study of the temperature effects of a jet traffic shutdown after 9/11 were later debunked by a subsequent study.
Now, what IS being discussed is the possibility of carrying large quantities of sulfur into the upper atmosphere (the stratosphere) to produce sulfur dioxide aerosols in an attempt to slightly reduce incoming sunlight and so partially offset global warming. This is an example of what “geoengineering” usually refers to. This would require huge amounts of sulfur compounds and many jet flights to even come close to the natural cooling effects of a major volcanic eruption, the most recent example of which was the 1991 eruption of Mt. Pinatubo in the Philippines. That eruption injected an estimated 15-20 million tons of SO2 into the stratosphere, which resulted in cool-ish summers over Northern Hemisphere land areas in 1992. Personally, I don’t ever see this happening because there would be too much public resistance to the idea.
But no one bats an eye when Mother Nature does it.
And the few news reports you see where supposed experiments involving the ground-level release of a few kg of sulfur compounds to test the idea of altering clouds are laughable. The EPA estimates that in 2023, 1.7 million tons of SO2 were released in the U.S. from anthropogenic sources. That is over 9 million pounds per day. Compare that to the “experimental” release of a few pounds by some headline-grabbing “researchers”. As I said… laughable.
A Major Reason for the Hysteria: Jet Contrails are Visible
Chemtrail hysteria would not exist if not for the fact that jet contrails are visible. Cars and trucks also produce huge amounts of water vapor, which is sometimes seen as condensed water in cold or high-RH conditions. The reason they don’t persist is that at the temperatures and air pressures present at ground level, the air can hold orders of magnitude more water vapor without cloud formation than jet-altitude air can hold.
But no one accuses car drivers (or car manufacturers) of purposely poisoning our air with chemicals, do they?
Yes, cars produce some chemicals as a by-product of combustion (all invisible), and through EPA regulations some of those chemicals have been greatly reduced with new fuel formulations, engine design changes, and catalytic converters. But cars are never blamed for producing chemtrails because, generally speaking, we never see those emissions (including the water vapor emissions). But we DO see jet contrails.
Finally, one part of the problem is that our public education system has produced too many science-illiterate adults. They are susceptible to crazy ideas spread by attention- (and money-) seeking charlatans, some of whom might be convinced that a chemtrail conspiracy exists. Too many people today seem to be incapable of independent, critical thought.
After all, who would doubt evidence such as this?:
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My next “chemtrails, etc” talk is March 24 — where I completely agree with Roy Spencer … http://www.climatecraze.com/talks.php … and expose many hoaxes. The audiences have a good laugh.
That photo is laughable. As though they would actually label it “chemtrails” even if that is what it was for. It would be a functional label related to the dispersal mechanism.
” the most recent example of which was the 1991 eruption of Mt. Pinatubo in the Philippines. That eruption injected an estimated 15-20 million tons of SO2 into the stratosphere, which resulted in cool-ish summers over Northern Hemisphere land areas in 1992.”
The cooling effect is only temporary. The long term effect is a purging of the stratosphere leading to more transparence to solar energy, cooler stratosphere and more SURFACE WARMING.
Look at the step cooling of the lower stratosphere a few years after the 1982 El Chicon and 191 Mt Pinatubo events. Then look at the surface warming in those periods and the 15y “haitus” which followed. Major eruptions lead to long term WARMING, not cooling. Climate scientists do not even notice .

re: “That photo is laughable. As though they would actually label it “chemtrails” even if that is what it was for. It would be a functional label related to the dispersal mechanism.”
Wit, of whom the soul wherewith be nothing less
than brevity itself, ought accordingly be brief, to wit,
lest the soul unwittingly be bereft, ere briefly, of its own.
Summarizing (b/c no one has time anymore to devote to full comprehension):
‘Brevity is the soul of wit.’
TMK the phrase was popularized by late-night radio talk show host Art Bell in the 1990s. Anyone could get a guest slot on Coast-to-Coast by claiming inside knowledge of the “truth” about chemtrails.
My audiences keep growing because they like to be informed and entertained.
In 1965 I first saw noted the dreaded contrails. I was nine years old. Lately I see 10 to 15 times as many. Proof of the conspiracy.
Alas, then I noted that air traffic had increased 10 fold, and the jets were bigger with more engines.
But I have photographic proof … those chemtrails are collaborating and have formed Godzilla like monsters.
re: “late-night radio talk show host Art Bell in the 1990s”
“Remote Viewing” – I can hardly wait until we do a page here at WUWT on Remote Viewing.
/sarc (of course)
The Esteemed Maj. Head Games, CEO of Technical Remove Viewing and purveyor of the Hale-Bopp Comet companion hoax!
RE: “. . . I completely agree with Roy Spencer . . .”
John, I also agree with Dr. Spencer. “Inconclusive“ was my observation/analysis of the ultimate effect of the “Project Stormfury” silver-iodide seeding of Hurricane Debbie on the morning of August 18, 1969.
I was one of several meteorologist crew members onboard the US Navy’s Weather Reconnaissance Squadron Four (aka VW4, aka the Navy “Hurricane Hunters”) aircraft that flew the low-level (1,000 ft above sea level), inflow-monitor mission for the Project Stormfury seeding of full-blown, North Atlantic, hurricane Debbie.
As the pilots flew into the teeth of hurricane Debbie’s rain-bands and eye-wall, we took repeated pictures of the plane’s horizontally scanning RADAR with a camera that was bolted to the RADAR’s scope.
What we observed was that over the hours surrounding the seeding, the hurricane’s footprint widened and the hurricane turned a bit. But the bottom line was that we were never able to isolate whether the spreading of the storm was natural or caused by the seeding (Source: Dr. R. Cecil Gentry’s Stormfury After-Action Report). “Project Stormfury” ended. I’m unaware of any other hurricane that has been “seeded” since.
Lastly, many kudos to those amazing Navy pilots and crew who safely and efficiently flew their WC121N hurricane hunter aircraft into the wicked turbulence of Atlantic hurricanes. The RADAR images of Hurricane Debbie’s footprint and position included altitude, which never deviated by more than +/- 100 ft from the assigned altitude of 1,000 ft. That is incredible aircraft control, given the circumstances!
Hi Bill. Nice to know you. Thanks for the details about Stormfury. I spent 3 years at Guam’s JTWC and worked with an ARWO (Dan Brown) who flew storms in the Pacific and Atlantic. We both are now in The Villages, FL. I run the local Weather Club and give many different climate/weather talks, including Why Airplanes Fly Into Hurricanes. One of my slides is about Project Stormfury and another project slide is attached.
Hi, John. Nice to meet you also. Please drop me a line sometime (bill@twoclimate.org) or call/text 435-315-8127. I think we have several things in common.
Bill. My email system would not allow me send a message to your email address. Please send one to me at … John@EJplace.com
I accidentally happened upon an “academic” paper in one of those journals that really has the opposite of pal-review, which in no review, showing a photo of three jets overhead; two showing no contrail and one showing a highly visible trail, which the author says shows evidence that the one jet was spreading a chemtrail. Yes, visibility alone is evidence, eventhough the jets were at different altitudes.
The University of Wyoming had a long project, twenty years plus and maybe as long as 40 years, with the State of Idaho, to use cloud seeding to aid winter snowpack in hopes of making hydrogeneration less seasonal. The results? Inconclusive.
re: “a photo of three jets overhead; two showing no contrail and one showing a highly visible trail,”
No word if this was ‘formation flying’ or just 3 random aircraft observed in the sky at various compass bearings at unknown heights at the same time, so –
-Differences in engine type can affect contrail creation (turbo-charged piston, turbine propeller, jet low bypass, jet high bypass) as can:
-Differences in different phases of flight (taking off and engine throttles advanced to achieve an assigned altitude, en route engines at cruise power setting, arrival at terminal airport and throttled back while descending or cruising at an intermediate FL (flight level) such as FL100 (10,000 ft) while transiting a large ATC controlled airspace like the DFW airspace.)
-Differences in Dew Point (RH) at various heights AND compass bearing relative to observer (familiar with hodographs and Skew-T diagrams?)
The movie Strategic Air Command has some really beautiful aerial shots of a B-36 flying. You can clearly tell when the B-36 had six turning and four burning as opposed to six turning and zero burning.
My recollection was that some research went into predicting weather for contrail formation as nothing kills stealth technology as easily as having a long contrail pointing to the aircraft.
I was amused at Roy Spencer displaying his sense of humor and impressed with his shout-out to Cliff Mass.
I’ve read that German fighter pilots loved to use the contrails from the big bombers to sneak up on the formations.
Obviously, dropping all those bombs in WW2 was just a cover for releasing all those chemicals that drove Adolf nuts! 😎
Cloud seeding is ineffective. It’s an “open secret”.
And of course chemtrails are nonsense.
China uses rainmaking a lot. I have been on an experimental farm where they routinely use low tech methods for increasing rainfall. I am not sure why it is claimed “not to work” or “be worth it”. In South Africa they use rockets and silver iodide (or similar). I don’t think this is a surprise. It has been known to work for decades.
Here is a list
https://zerogeoengineering.com/2021/8-chemicals-used-in-artificial-rain-cloud-seeding/
re: “am not sure why it is claimed “not to work” or “be worth it” ”
Its in the papers being referenced; I remember reading papers on cloud seeding efforts in previous years a decade back and seeing the same dismal results being reported.
Who knows WHAT the Chinese are doing – saturating the convective storms with silver iodide? At 10x the amounts normally tried? Don’t know, just conjecturing here …
Remember, THOSE doing the cloud seeing (and being paid for it) do NOT have an incentive to report adverse (no increase in precipitation) results, rather, the incentive is to solicit MORE business by reporting positive results … have we not learned this lesson yet?
Back during the 50s drought “rain makers” were scouring Texas. Some used a cannon, said to be an attractant to sharks in Vera Cruz causing attacks. Weren’t any clouds in Texas, don’t know about Vera Cruz.
I’m in Texas. I’ve seen Texas weather. Some is pleasant, some is not so pleasant. Seen long dry spells, seen very wet springs too. It varies …
Learned forecasting (as an amateur) from one of the best – Harald Taft, Ch 5 weatherman, and ex-mil weather forecaster in WW2. RIP Harold.
We’ve got a good one, Alan Holt, channel 3 in Corpus Christi and they give him plenty of time that he uses explaining well. End of 50s drought which started in late 40s was something like half of average state rainfall for the last three years, 1954-56, big flood in spring 57.
well, if China says it works… after all, why would they lie about anything?
“well, if China says it works… after all, why would they lie about anything?”
I don’t know, and you won’t say why.
I assume you are just being mindlessly sarcastic for no particular reason. What’s your opinion about “well, if America says it works… after all, why would they lie about anything?”
Ignorance, maybe? Trying to separate suckers from their cash? Hiding inconvenient truths about government misadventures?
Which particular “Chinese” lies are you referring to?
re: “Which particular “Chinese” lies are you referring to? ”
Where do you want to start? Tofu Dreg Construction? Failing Chinese economy? Continuing series of industrial fires set as a result of workers not being paid? Where do you want to start?
Reporting by sources inside and outside China:
China Observer channel
https://www.youtube.com/channel/UCT2kPBcD6tXn8TP_aV7BmgA
China Fact Chasers:
https://www.youtube.com/channel/UCwHPRkLWbL_guuBMGxKe2aQ
Are you saying that “Failing Chinese economy?” is a Chinese lie?
Who says so, and how do you know it’s a lie? Maybe it is failing, for all I know. Which particular Chinese people say so, or are you bigoted against Chinese people in general?
If Chinese Americans say the Chinese economy is failing, are they lying, or telling the truth?
If you are implying that Chinese politicians lie sometimes, I would say that all politicians are capable of lying when it suits them. I can’t see why any particular racial group should be different.
Maybe you could name the Chinese liar, and support your opinion with verifiable fact, but I doubt it.
China, through China state media (e.g. CGTN) is not what it seems to be. I supplied several sources that through “ground truth” and various observations allow ‘truth’ and a more accurate picture of China and China’s problems to be determined.
You I mostly see flailing, to be honest. You’re verging into non compos mentis territory again too.
“China, through China state media (e.g. CGTN) is not what it seems to be”
OK, what is it, if it isn’t what it seems to be? You can’t really say, can you?
It seems to be a country with a population of about 1.4 billion people, but if you know otherwise, why are you keeping it to yourself?
You write “You I mostly see flailing, to be honest.” Do you often have these hallucinations- seeing things that don’t actually exist? It’s my observation that honest people generally have no need to try to impress people with claims of honesty. Fraudsters, conmen, politicians, on the other hand – often make extravagant claims that they as honest as the day is long. Right up to the time they are convicted.
Others may value your opinions, and good luck to them! I don’t.
You might consider offering comment about the physics involved with the visible contrails observed, but I’m guessing you have zero to contribute. Am I wrong?
I’m aware, but it doesn’t work. Nature wins again.
The UAEs use rainmaking too, probably more than China (very ich, arid). Doesn’t work there either. It rained more before (1987-2002) than after (2003-2019) the initiation of cloud seeding operations, and this study still claims it’s effective. Very weak sauce.
https://www.mdpi.com/2073-4433/12/8/1013
Apart from being an expensive silver compound and being toxic, why else wouldn’t you dump it in a cloud to poison the soil?
I asked my younger sister if she ever did the mole calculations in high school chemistry class. She said no, as her section was “taught” by a football coach filling in. So my example of why homeopathy was impossible was outside her education. And that was the school system of fifty years ago.
I think Spencer’s noting that clearing clouds with directed microwaves would require gigawatt level power would also go over the heads of many public school victims, I mean, graduates.
re: “Does the Air Force Own the Weather in 2025?”
.
April 1st article released early? (Flat earthers going to have a field day with this one!)
Remember, everything that you eat, breathe or contact that might harm you is TOXIC no matter what the concentration is.
But claiming that toxins are harming you without naming the toxin or the concentration is a little silly. In reality, beans, peaches, potatoes and mushrooms are all toxic. But I’m not going to stop eating them because of that.
Almost everything causes cancer in California. It says so on almost every label!
Growing up in the UK they were “Vapour Trails”.
Looking at pictures of the sky over SE England in Summer 1940 I often how those pilots had time to turn on the Chemtrail machine.
Just a couple historic notes –
Contrails from multiple WW2 piston-powered aircraft at 21:00 point:
.
https://youtu.be/raMcFQ_wJjQ?t=1260
.
15:55 into the video ME262 (jet aircrat) leaving contrail:
.
https://youtu.be/8OXuPV85qVc?t=951
I understand jet contrails but you failed to mention at least two known secret government projects which used spray into the air using jets/aircraft.
The first is operation Sea Spray in which the Navy sprayed marcescens and Bacillus bacteria over San Francisco in 1950’s (information not released until the 70’s)
The next was known as the Dugway Sheep Kill in which thousand of sheep were killed with anthrax sprayed from a jet.
Next throw in agent orange and its unintended effects
Now you have the seeds of a very ‘plausible’ conspiracy theory (however wrong)
Government secrecy is the root of the problem
Where the government is concerned, conspiracies are a day at the office.
Has this been intentional conflation of “spraying” with an agricultural activity once known as “crop dusting”?
Does anything coming from an airborne platform NOW have to 1) come from a “jet” and 2) be “sprayed”?
This has the makings of propaganda / agitprop targeted at the average mind of the public, the making of a ‘battle space prep’ or something akin (set the stage for ???) to battle space prep.
Jim, you wrote –
“This has the makings of propaganda / agitprop targeted at the average mind of the public, the making of a ‘battle space prep’ or something akin (set the stage for ???) to battle space prep.”
Are you a strong believer in the need to prepare for “space battles”? Do you believe that adding CO2 to the atmosphere makes it hotter, creating some sort of “greenhouse effect”?
Oh dear, that would make you sound quite irrational, wouldn’t it?
David Travis of the University of Wisconsin published a paper in Nature on the slight increase in temperature following the grounding of virtually all aircraft following 11 Sept 2001 attack. He suggested that the absence of contrails is what caused the temperature increase. I believe this is the Travis who co-authored my paper on the reduction in sunlight caused by abundant contrails over Switzerland while I was there teaching a course. (I recorded sunlight with a visible light radiometer connected to a data logger while I was indoors teaching.)
Forrest M. Mims III
re: “He suggested that the absence of contrails is what caused the temperature increase.”
The usual caveat, of course, applies:
correlation =/= causation*. (i.e. correlation does not imply or equal causation)
It would be interesting to know the average length (lifetime) of contrails you might observe on any given day. Different times of the year might yield different Dew Points (RH) at aircraft flight levels in the airlanes too. I am not at all familiar with upper air characteristics over Europe.
.
.
* The inability to legitimately deduce a cause-and-effect relationship between two events or variables solely on the basis of an observed association or correlation between them in time.
as I mentioned, that 9/11 study was subsequently debunked by a more careful study. There are biases in model output statistics (MOS) forecasts that are persistent, depending upon weather regime, and the original study did not account for that. I’ll dig the reference out if you cannot find it.
“There are biases in model output statistics (MOS) forecasts that are persistent . . .”
Yes, such as believing the utility of “forecasts” made by models.
A model might indicate a 50% likelihood of rain. In other words, it is equally likely to not rain. Brilliant. What to do? Take 50% of an umbrella?
Seems reasonable. I notice when a cloud passes over, the surface temperature drops. Cloud passes, temperature goes up.
Of course, some “climate scientists” seem to believe that high cloud increases temperature by reducing the amount of insolation reaching the ground! Apparently due to clouds at -40 C, heating the ground, or some other silliness.
Anything between the surface and the sun reduces surface temperature. Places like Death Valley shows the result of minimum reduction in sunlight – little H2O in the atmosphere, for example.
As to rainmaking, the dances and chants performed by my distant ancestors worked as well as the latest technology, and were far cheaper.
re: “Seems reasonable. I notice when a cloud passes over, the surface temperature drops. Cloud passes, temperature goes up.”
Um, one doesn’t really see much of a fluctuation of air temperature (assuming some wind is present, as it normally is, even if just a variable wind), so I would ask you, “Where did the heat energy go IF there was actually a drop in temperature?”
You might be referring to feeling ‘hot’ with the sunlight itself hitting your skin and sweating (have to be careful with these sorts of assumptions going forward, what with so-called “AI” being capable of entering the chats at times) in which case your statement carries some validity from human senses (touch, sight, hearing, smell and taste) point of view.
Jim, you asked –
“Where did the heat energy go IF there was actually a drop in temperature?”
If you reduce the amount of radiation reaching the surface, the temperature drops – no IFs involved.
Why would less radiation reaches the ground? Because clouds reflect infrared as well as visible light. I know you won’t believe me, but NASA agrees, saying “Low, thick clouds reflect solar radiation and cool the Earth’s surface.”
You can see the effect by watching a Campbell-Stokes recorder, or just placing a thermometer on the ground, and watching the temperature change as clouds come between the sun and the thermometer.
If you disagree, I always appreciate correction supported by verifiable fact.
You would appear to have either moved the goal posts on this, or did not faithfully establish the conditions under which you made the claim “I notice when a cloud passes over, the surface temperature drops.”
What we may have here is a failure to communicate.
I notice that when a cloud passes over, the surface temperature drops.
If you disagree, I always appreciate correction supported by verifiable fact.
I typed slowly, in case you are a bit slow.
Contrails have been with us ever since aircraft have been able to fly high enough.
I can certainly remember seeing them in the 1970’s and l even taken photos of a growing contrail back in 1980.
As you say the reason they can ‘spook’ people is because there visible and when the conditions are right, they can grow quickly and look very dramatic. Ever since childhood l have had a keen interest in the weather and so was never worried about seeing them as l understood how they were caused. They can certainly help to add spice to a sunrise or sunset.
Very nice Dr. Spencer, really important information. I have question, if the temperature is minus 30 to 50 degrees Fahrenheit at that altitude why doesn’t the water vapor freeze and fall to earth as hail, snow or eventually rain?
Size of the ice particle is significant in answering the question. Obviously the contrail ice particle are a similar size to cirrus cloud particles.
too little water at too high of an altitude.
‘Chemtrails’ are a good example of abject human stupidity.
Einstein is supposed to have said, ‘There are only two infinite things: human stupidity, and the universe. I am not sure about the universe.’
Completely agree with your analysis of “chemtrails” (contrails), however, we have seen on this site pictures of contrails forming in an off-shore wind farm. Obviously, no jet engine exhaust to trigger it. Given the just-right conditions of humid air very close to the condensation point, drawing even a little energy out of the wind, which the turbine blades (like aircraft wings) are designed to do, can lower the local temperature/pressure enough to trigger condensation. As you said, the condensation itself can draw sufficient energy from the air to propagate more condensation, creating the billowing cloud effect sometimes seen.
I would have to see a photo to know what is happening. I HAVE seem a photo where windmills disturb the boundary layer in the presences of fog, causing mixing of dryer air from aloft downward where clear streaks are formed in between the fog streaks. Maybe this is what you are referring to.
Roy, the phenomenon happens without the fog being above the base of the tower in the photos I’ve seen. Hiskorr points out the likely mechanism.
The air loses energy to the turbine, its temperature must drop, and may create the fog (cloud) apparent in photos on the internet.
Would you agree?
re: “Obviously, no jet engine exhaust to trigger it.”
Today’s modern high-bypass jet engine has 60% and a bit more just plain air coming out the rear … we aren’t flying pure jets (excepting some fighter aircraft) anymore nor are any of the commercial air transport or mil air transport aircraft flying even the low-bypass jet engines first put in service in the 70’s decades ago.
The low-pressure seen off the backside of the first and second fan blades allows condensation of water vapor into what is then seen as ‘contrail’ on the output side of a high-bypass jet engine WHEN conditions allow (high Dew Points as opposed to low Dew Point numbers at height.)
Using a Skew-t diagram you can determine the Dew Point at altitude above a balloon launch site:
https://wildcardweather.com/2015/02/21/learn-to-read-a-skew-t-diagram-like-a-meteorologist-in-pictures/
Jet engine exhausts contain a lot of H2O generated from burning hydrocarbons, plus a lot of waste heat. All this is released into the atmosphere at altitude, plus lots of condensation nuclei.
According to “The Formation of Exhaust Condensation Trails by Jet Aircraft
H . A P P L E M A N Hqs., Air Weather Service, Washington 25, D. C”, the first reference I came across, about 10,000 calories of heat is released into the atmosphere for every gram of fuel burned.
Edward Lorenz titled a paper “Predictability: Does the Flap of a Butterfly’s Wings in Brazil Set Off a Tornado in Texas?”.
Multitudes of jet aircraft injecting vast quantities of CO2, H2O, condensation nuclei, and heat into a chaotic atmospheric system, are quite possibly going to have more of an effect than the flap of a butterfly’s wings. Nobody knows what the effects might be – for better or for worse.
Given the amount and temperature of heat released, and that IR radiation penetrates the atmosphere without significant reduction (step into the sunlight if you don’t believe me, or stand near a fire), would thermometers on the ground be sensitive enough to respond? What about satellite microwave soundings of the layer occupied by thousands of heat-spewing aircraft?
Not really important, just wondering.
re: “Jet engine exhaust”
Doesn’t explain why contrails are nonexistent some days, prevalent on others (same ‘exhaust’ gases are ejected from similar aircraft each day … no?)
Doesn’t take into account the large distances and associated large volumes of the atmosphere products of combustion are “injected”. Suggest some calculations are due/needed to show how dispersed these components (exhaust gases and heat) really are.
All jet “exhaust” (the air mass which exits to the rear of the engine) is not “exhaust” gases containing (H2O and CO2) resulting from a combustion process. High bypass jet engines incorporate a fan stage known as a turbofan which ‘drives’ air out the rear of the engine too bypassing the ‘engine core’. A large amount of air, over 50% of that entering the turbofan engine exits this way. ‘Contrail air’ (!) is created by turbofan action too, not just the presence of exhaust gases.
A good authoritative reference on aircraft turbine engines can be found here:
#Aircraft Gas Turbine Powerplants
https://archive.org/details/JeppesenAircraftGasTurbinePowerplantsCharlesEOtisC2002
Chapter 3 beginning page 32 goes into turbine engine designs.
re: “What about satellite microwave soundings of the layer”
I would suggest you take a look for yourself, using the link below, and report back with your conclusions? You can choose your spectra for observation on the left hand side of the currently displayed image then click a region for display.
https://weather.rap.ucar.edu/satellite/
Jim, you wrote –
“Doesn’t explain why contrails are nonexistent some days, prevalent on others (same ‘exhaust’ gases are ejected from similar aircraft each day … no?)”
Of course it does! I suppose you don’t believe that clouds are nonexistent on some days, prevalent on others. The atmosphere exists all the time, no?
I asked whether satellite soundings would detect the output of aircraft heat emanations. Obviously, either you don’t know, or you are being purposely unhelpful.
You also wasted time writing “All jet “exhaust” (the air mass which exits to the rear of the engine) is not “exhaust” gases containing (H2O and CO2) resulting from a combustion process.”
Well, gee, that’s what I said (although I phrased it differently), wasn’t it? Can’t you comprehend English, or do just enjoy acting the goat? Maybe you could disagree with something I wrote – but I doubt it.
I don’t think you understand what is going on here. I don’t think you have an understanding of what is involved, I don’t think you have an understanding of what tools are available, today, to possibly answer some of the questions you ask. We’re verging on non compos mentis territory.
Jim, you wrote “I don’t think you understand what is going on here.” I hope you won’t mind if I assign no value at all to your opinion.
I agree that you are obviously firmly occupying “non compos mentis” ground.
Maybe you could supply some more unsubstantiated opinions, and hope that someone values them more than I.
I have personally seen weather modification caused by technology–when I happened to get stopped by a traffic light in mid winter beside a Ballard fuel-cell bus being tested. While stopped, with the prevailing temperature and dew point being ideal, the exhaust from the bus immediately condensed and enveloped all of us in a thick fog.
When the light turned green nobody moved because–nobody could see the traffic light, or much else for that matter. The air had been clear when we stopped except for the billowing white cloud following the bus.
So darn right technology can cause weather modification. I remember at the time musing what was going to happen when there were thousands of these things operating, in winter, in that kind of climate.
So, exhaling in winter and getting a cloud is weather modification?
Seems there is a minimum area/volume needed to define weather modification.
Maybe you have seen steam rising from hot asphalt during the beginning of a shower on a hot day?
what about 8 billion people breathing out water vapor (not to mention CO2)?
One person is quite enough. There is no minimum disturbance required to create unforeseeable outcomes in a deterministic chaotic system.
No “equilibrium”. No “reversion to the mean”.
Just unpredictability with nobody able to predict the weather than a smart 12 year old.
But no one accuses car drivers (or car manufacturers) of purposely poisoning our air with chemicals, do they?
Yes. They claim CO2 is a pollutant, aka poison.
I said “purposely”.
I suppose the intentional addition of tetraethyl lead compounds (when it was known to be poisonous to humans) to gasoline might count.
Probably the reason nobody “accuses”car drivers or manufacturers of intentionally “poisoning” the “air” with chemicals broadly, is because governments actively support the manufacture and use of “cars”.
BEVs apparently convert their tyres to airborne microparticles at a far greater rate than their lighter and less powerful ICE counterparts. Who cares?
I intentionally “poison the air” by allowing toxic solvents to evaporate into it. Letting paint dry. Spraying weeds or bugs. Burning leaves and rubbish.
ignorance is no excuse, is it?
Just like “global warming” due to heat as a result of human activities, it’s a price you have to pay because I like being comfortable.
re: “I intentionally “poison the air” by allowing toxic solvents to evaporate into it. Letting paint dry. Spraying weeds or bugs. Burning leaves and rubbish.”
Now do volcanic eruptions. Where do we stack up against the ’emissions’ of Mother Nature with that considered? And REMEMBER we have continued emissions of this type or nature from lava flows and other fissures opened-up to the molten core deep below and beneath our feet (what do you think makes geysers and hot springs?)
Oh – and wildfires, include those too. Lightning-induced wildfires count too. Include everything.
I’m sure there are other ‘processes’ in nature that create conditions hazardous to life as well that I am not aware of.
The OP wrote –
“But no one accuses car drivers (or car manufacturers) of purposely poisoning our air with chemicals, do they?”
Are you complaining about my comment on principle, or do you actually have a reason? Why should I “do volcanic eruptions”?
Can’t you comprehend English?
Failure to answer question posed? To wit: “Where do we stack up against the ’emissions’ of Mother Nature with that considered?”
(I don’t know that your comprehension abilities are up to par perhaps …)
Man’s (mankind including you, paint fumes et al) emissions compared to the emission by Mother Nature via volcanic eruptions et al, are we the bigger ‘polluter’ on the planet, or is Ma Nature? Pretty simple question, but it escaped you?
Here’s what the OP wrote –
“But no one accuses car drivers (or car manufacturers) of purposely poisoning our air with chemicals, do they?”
You asked me “Where do we stack up against the ’emissions’ of Mother Nature with that considered?”
You then attempted to confuse the issue by asking “are we the bigger ‘polluter’ on the planet, or is Ma Nature?”
Don’t you know? Why ask me? Do you regard me as some sort of absolute authority in trying to figure out what goes on in a tortured mind?
Are humans not part of nature? What do you define “emissions” as? What is a “polluter” in your mind?
You sound as if you’re one of those people who believe that adding CO2 to the atmosphere makes it hotter, or who believes that unspecified “emissions” cause some sort of unspecified “pollution” with unknown outcomes.
Are you one of those people?
Surely the correct word is solidification rather the condensation
We performed hyperspectral imaging of contrails 28 years ago, measuring radiance, composition, and time evolution between 0.8, and 2.5 microns, for jets flying overhead in arranged paths. An example of the evolution of the radiance of a contrail is attached in the plot. It was interesting science in terms of jet contrail evolution, but the bottom line, as noted in the article here, was that the contrails’ climate effects were negligible.
Contrail forcing is a serious competitor to the CO2 narrative. A “best estimate” in this context is highly politicized, and it is quite naive not seeing this. It is a downplayed figure to get contrails out of the way. It is “tactical science”, not actual science. Just two quotes pointing out the real magnitude of this issue..
This result shows the increased cirrus coverage, attributable to air traffic, could account for nearly all of the warming observed over the United States for nearly 20 years starting in 1975
(Minnis et al 2004)
The potential effects of contrails on global climate were simulated with a GCM that introduced additional cirrus cover with the same optical properties as natural cirrus in air traffic regions with large fuel consumption (Ponater et al., 1996). The induced temperature change was more than 1 K at the Earth’s surface in Northern mid-latitudes for 5% additional cirrus cloud cover in the main traffic regions.
(IPCC special report on aviation 1999)
Also it is not true Travis et al 2004 have been “debunked”. They too, though indirectly, pointed out the major role contrails play in the (not so) global warming, which occurs mainly in the NH. It was just argued against by, again, “tactical science”.
Other events like the icelandic volcano eruption 2010, or covid related lockdowns since then totally vindicated the massive cirrus pollution, and equally massive forcing, that contrails provide.
https://greenhousedefect.com/contrails-a-forcing-to-be-reckoned-with
“The potential effects of contrails on global climate were simulated with a GCM.”
Predicting the outcome of a chaotic system? Apart from a “climate scientist”, who would believe it?
From the article –
“Contrails reduce the amount of sunlight reaching the surface (a cooling effect), but that is more than offset by their reduction in the infrared (IR) cooling of the climate system, leading to a net heating.”
Of course, this is complete nonsense, apart from “a cooling effect”. If contrails make the surface colder, no amount of reducing the rate at which that cold surface cools is going to increase its temperature!
It continues to cool. The author hasn’t accepted the reality that a drop in temperature is cooling. Whether the rate of cooling is slowed (say by putting hot coffee in a thermos flask), it doesn’t result in an increase in temperature.
Play with words all you like, falling temperatures are not “warming” or “heating”.
Chemtale hysteria is a metastasis of the climate alarm propaganda of “weather weirding”. It’s a mutant theory for why the weather went weird and whiplashed. By people who don’t trust what the government says about climate change, but believe the spin that the weather is doing something unusual.
1– Contrails are nothing new – they are visible in WWII footage of 4 engine (and probably 1&2) piston engine bombers.
2–The first I heard of them was on Art Bell’s overnight show probably in the 1990s.
The US has been cooperating with Morocco for years on weather midification
Here’s the patent: https://zerogeoengineering.com/wp-content/uploads/2017/09/US20100074390A1.pdf
More to read: https://zerogeoengineering.com/2024/did-moroccos-al-ghaith-cloud-seeding-operations-trigger-deadly-flooding-in-spain/
How is it you Keepers Of Odd Knowledge (K.O.O.K.) cite the same website “zerogeoengineering”?
You do know, too, that issuance of a patent is proof of nothing? Not even a working prototype is required these days.
https://duckduckgo.com/?q=%22working+prototype%22+patent&t=ffcm&ia=web
I was sitting on a boat at Lake Powell a few miles downstream from Bullfrog Marina on a clear summer day. Numerous jets passed overhead in the course of the morning and the contrails they left behind remained stationary above me. They grew until the sky was quite filled with clouds.
Evaporation from the huge lake was no doubt the contributor in the otherwise desert area since no movement in the upper air was observed. It is impossible to know if the clouds would have formed without the boost from the jet exhaust, but it certainly was a fascinating process to watch.
Next time, pop over to the website linked below and click on a close location under heading “Skew-T/Log-P diagrams” and observe the temperature vs dew-point profile (the two usually jagged lines plotted) versus altitude … also note the wird barbs on the right side of the image plotted versus the same heights.
https://weather.rap.ucar.edu/upper/
Thanks for the link Jim. Unfortunately, unless you are in a rare spot where the Henry Mountains are visible, cell phone service is not available at Lake Powell unless you are at Bullfrog or Wahweap, and even satellite internet is limited.
Does that chemtrails box go to 11?
Film at – “Eleven”, said every TeeVee news operation in 1970 …. (the time it took to process and develop 16mm film and add-in the sound track)