The Seven Percent Solution
A Sherlockian Investigation Into Cirrus Clouds, Jet Engines, and the Hidden Hand in the Sky by Dr John H. Watson
Author’s Note by Dr. John H. Watson
It has been many years since I last chronicled one of Mr. Sherlock Holmes’s more curious investigations, and never before have I taken up the pen to recount a case which spans not the fog-bound alleyways of London, but the rarefied and silent vaults of the upper atmosphere.
The matter at hand is no ordinary one. It concerns not a murder, a theft, nor a coded message—but rather, a scientific anomaly that has long drifted overhead, scarcely noticed, yet vast in its implications.
When Holmes first turned his attention skyward, I admit I doubted his instinct. "Clouds?" I asked him. "Why, surely they are the most ephemeral of subjects!" But, as is so often the case, the great detective saw what others did not.
What follows is the first in a series of investigations into a most peculiar aerial phenomenon: the unseen residue of our own industry, drifting aloft in trails of white, casting a veil of our own making upon the heavens.
I beg the reader's indulgence, then, as we depart from 221B Baker Street and ascend—both literally and deductively—into the very skies above us.
— J.H. Watson, M.D.
Something's Afoot in the Upper Atmosphere...
It was on a brisk April morning, the clouds scudding high and thin above Baker Street, when Mr. Sherlock Holmes set down his violin mid-sonata, turned abruptly to the window, and remarked, "Watson, have you ever considered the artificial nature of those clouds?"
I glanced upward, seeing only the pale streaks that passed, as always, without comment from the common observer.
"Contrails, Holmes? Harmless vapour from engines."
"So we are led to believe," he muttered. "And yet, Watson, there is ash in the air—ash where there should be none. The game, my dear fellow, is afoot."
Chapter 1: A Curious Residue in the Sky
Holmes had been poring over a most curious scientific paper published in the Proceedings of the National Academy of Sciences. It detailed measurements of particles embedded in ice crystals of cirrus clouds — the high, wispy formations that often trace the upper troposphere like ghostly fingers.
What intrigued Holmes most was not merely the presence of these particles, but their composition. Using advanced mass spectrometry, the researchers had found that particles acting as ice nuclei (IN) — seeds around which ice crystals form — were not all of natural origin.
One particular category caught his eye: mineral dust and fly ash, which accounted for 33% of the heterogeneously nucleated ice particles (those forming under lower humidity conditions, where impurities matter most).
And of those, 20% were identified as fly ash — a byproduct of high-temperature combustion.
"Watson," Holmes said, tapping his notes with a bony finger, "20% of 33% is 6.6%. Thus, 6.6% of cirrus cloud formation is driven by fly ash particles."
I nodded, impressed.
"Now consider," Holmes continued, pacing. "Cirrus clouds cover approximately 35% of the Earth at any given time — including sub-visual layers detectable only by infrared sensors. Multiply that by 6.6%, and you arrive at an artificial influence over 2.31% of the Earth’s skies."
“Why, then… 2.31% of Earth’s surface, covered in fly ash-seeded cirrus at any time!”
“Not quite, Watson,” Holmes replied, eyes glittering. “Let us not stop at fly ash alone.”
Chapter 2: Ashes Aloft
Fly ash, Holmes explained, consists largely of spherical silicate and metallic mineral particles, formed by rapid cooling after combustion. Their high sphericity and composition make them excellent candidates for ice nucleation.
"But there's more," Holmes said, gesturing toward an electron micrograph.
"For the same study reported that an additional 25% of cirrus ice nuclei were seeded by metallic particles — metals such as aluminium, barium, vanadium, titanium, and iron, which are found not only in terrestrial sources but in jet fuel combustion ash, released directly into the upper troposphere.”
My eyes widened.
"Add that to the fly ash contribution, and we have 31.6% of cirrus clouds seeded by particles of anthropogenic, industrial origin."
He lit his pipe with a flare of theatrical satisfaction.
"Nearly a third of all cirrus clouds, Watson — born not of nature, but of our engines."
“The total coverage over the earth of cirrus clouds, Watson, including those undetectable to the human eye and only picked by the ingenious technology that is Infra-red satellite imagery, is 35%.”
“Now take 31.6% of 35%...”
I scribbled on my notepad. “That would be… 11.06% of the planet’s sky!”
“Indeed, Watson. More than one-tenth of the Earth’s surface is, at any given time, beneath an artificially induced cirrus veil — a climate layer not born of nature but forged in furnaces and turbines.”
“But surely,” I protested, “fly ash is captured at coal plants. Electrostatic precipitators, bag filters… the particles never reach the clouds!”
Holmes nodded. “Just so. The fly ash of which Cziczo speaks is not escaping from modern smokestacks. No, Watson — the skies themselves are the chimney. We must look not to chimneys, but elsewhere...”
And soot? Holmes dismissed it with a wave. Soot, or black carbon, is hydrophobic and requires high humidity to nucleate ice. Multiple studies have shown it contributes only ~3% to cirrus ice residuals. Its role is negligible — indeed, some have even proposed its use to suppress contrail formation.
Ash, however, is another matter entirely.
Chapter 3: The Metallic Clue
The source of the metallic particles fascinated Holmes. While fly ash primarily comes from coal combustion, much of it is now captured by electrostatic precipitators. Yet the high-altitude presence of fresh ash suggested a more elusive source.
"Jet fuel combustion," Holmes declared, "produces high-temperature ash with metallic and mineral components. These particles are spherical, much like fly ash — and just as potent in seeding ice."
Jet engines, as Holmes explained, burn fuel at high temperatures, ejecting combustion ash into precisely the atmospheric region where cirrus clouds form. These ash particles are often spherical — a signature of rapid solidification at combustion temperatures — and chemically resemble fly ash in their metallic and silicate content.
They do not emit soot alone,” Holmes said. “That is the common misconception. No, Watson. It is the ash, not the soot, that bears responsibility.”
I was struck by the elegance of it. The ash particles of jet fuel are small, rich in metal oxides, unfiltered, and perfectly positioned in the upper atmosphere to act as seeds for ice crystals — forming thin, heat-trapping clouds that, unlike their lower cousins, do not cool the Earth but warm it.
Holmes reviewed further literature — laboratory studies confirming that metallic particles, including those found in aircraft exhaust, readily form metallic minerals upon atmospheric aging. These materials often surpass even mineral dust in their efficiency at ice nucleation.
“They are rivals,” he concluded, “with the natural mineral dusts lifted by sandstorms and volcanoes.”
“And as mineral dust is angular and irregular, the spherical shape of jet combustion ash provides a forensic signature. Just as one can distinguish fly ash from dust by its morphology and mineral ratios, so too might one mistake jet ash for fly ash, unless particle origin is carefully examined.”
Could jet fuel ash then be misidentified as fly ash in studies?
"Quite possibly," Holmes mused. "Given their shared morphology and similar composition, jet combustion ash might account for a significant portion of what is observed as fly ash."
“And since commercial aviation predominantly occurs in the upper troposphere — right where cirrus clouds form — the circumstantial evidence became increasingly damning.”
“If we conservatively assume that much (~80%) of the 25% metallic contribution originates from jet emissions, we approach a striking conclusion:
I scribbled again on my notepad.
0.80 × 25% = 20% of cirrus clouds formed on jet fuel ash.
0.20 × 35% (total cirrus coverage) = 7% of Earth's surface under cirrus clouds formed by the very same aviation ash.
“Artificially seeded cirrus clouds — driven by aviation-sourced ash — now veil over 7% of the Earth's surface.”
“It is a capital mistake to theorize before one has data… but once the data speak, deduction is elementary.”
And here, the data spoke volumes. A powerful, overlooked climate signal hiding in plane sight. A global, high-altitude fingerprint from the engines of progress.
Holmes leaned back, steepling his fingers. "Watson, we have reached what I call the Seven Percent Solution."
Epilogue: A Veil of Our Own Making
“Cirrus clouds are not mere whispers of weather,” Holmes said gravely. “They trap outgoing infrared radiation and contribute to net warming — especially when seeded artificially.”
He turned to me.
"And so, Watson, we’ve uncovered a silent, airborne fingerprint of human activity — not industrial stacks alone, but the very engines that knit our skies together in trails unseen by the untrained eye."
I wrote down his final words as he spoke them:
“What was once sky has become canvas — and we, the unwitting artists.”
“Or perhaps some of us are not so unwitting…”
And with that, he turned back to his violin.
Coming Soon: The Seven Percent Solution, Part II: Moriarty in the Stratosphere?
What is the geopolitical significance of controlling cloud cover? Is the atmosphere being altered by some nefarious design? Join Holmes and Watson as they follow the trail even higher...
📚 References & Source Material
1. Cziczo et al. (2004) – Measurements of the concentration and composition of nuclei for cirrus formation
PNAS Link2. Kärcher et al. (2018) – Soot as a poor ice nuclei source for cirrus clouds
Link3. Möhler et al. (2005) – Ice nucleation properties of soot particles
AGU Journal Link4. Rolls Royce Patent US 9518965 – Jet engine contrail suppression via black carbon
Google Patents Link
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“The deduction, Watson, is elementary. Especially when dealing with the elements.”
Disappointingly short Doctor, and, in case the great man himself has not already read this, might I suggest a small clarification to chapter 2 based on the following extract from your last reference - The attempted hiding of vapour trails through introducing black carbon into the aircraft engine effluent (U.S. Pat. No. 3,289,409A) results in additional emissions of a species (black carbon) which is known to have an environmental warming impact. - This would indicate that soot is used to suppress only the visibility of contrails.
Paging Jeremy Brett ....