08. The Riddle at the Heart of Ice

A Study in Infra-Red

Part eight – The Riddle at the Heart of Ice

To the trained eye there is as much difference between the black ash of a Trichinopoly and the white fluff of bird's-eye as there is between a cabbage and a potato.” Sherlock Holmes

If an aviation-induced cloud, covering up to 50,000km2 and lasting for 18 hours, comes into being solely from a contrail which in turn originates as a result of an aircraft passing through a region of the atmosphere, what causes it?

We know that the water from the jet engine as compared to atmospheric water in a contrail is relatively insignificant (conservatively estimated as being around 24,000 times less). 


 “Nearly all of the contrail is created from the moisture in the atmosphere.”

Jet engine water may have contributed to the initial line-shaped trail, but with insufficient atmospheric water, this soon dissipates as a contrail requires over 90% relative humidity (RH) at flight altitude.

If there had been sufficient atmospheric water in this particular case, why were cloud formations not already present?

What was the main ingredient the jet contributed, if not water?

Again, in this particular case, atmospheric aerosol content, of the kind that readily entrains ice crystals, can’t have been high enough, otherwise cirrus clouds would already have been present, obviating the need for the term – “aviation-induced cloud”. Only about 1 in 100000 aerosols present in the upper atmosphere will nucleate ice.


Contrails are clouds formed when water vapor condenses and freezes around small particles (aerosols) that exist in aircraft exhaust.

So the jet must have contributed additional and specific aerosol content or enhanced the ice nucleating potential of the atmospheric aerosol content in some way, or both.

At its peak, after 7 hours, the cirrus cloud covering 50,000 km2 with an average thickness of 0.5 km, would have a volume of around 26,000 km3. As the more developed cirrus clouds have an ice crystal concentration of around 1-2 cm3 after about 7 hours, and the initial quantity of particles emitted from the jet basically remains the same whilst entraining more and more atmospheric water onto each individual ice nuclei, we can assume a total of around 39 x 1019 particles emitted during this single event.  

Recall from part 7 that the optimum number of ice nuclei of the suggested aerosol Bismuth tri-iodide (BiI3) for inducing cirrus cloud precipitation was in the range of 10 to 15 ice nuclei per litre, whilst the number that would bring about an over-seeding regime was above 15 ice nuclei per litre. The ice nuclei concentration of our aviation-induced cirrus cloud at its greatest extent of 50,000 km3 after around 7 hours would be in the range of 1000 – 2000 ice nuclei per litre.

Given that, a potential 8% global increase in cirrus cloud cover over 4 decades, resulting in a global forcing of 1.6 W m2, has been correlated with air traffic, it could well be that international aviation has already set up an over-seeding regime on a global scale, rendering attempts to maintain a “goldilocks” range futile. 

Recall also from part 4 that this aerosol fingerprint is observed in the record of upper atmospheric humidity, revealing a decline, counter to a CO2 induced warming but in line with aerosol induced cirrus cloud formation entraining water from the surrounding atmosphere.


It remains to identify this elusive aerosol, traces of which, it would be logical to assume, are detectable in the cirrus clouds themselves. 

Of Particular Importance


We know that cirrus clouds, natural and artificial, require very specific particles that act as ice nuclei.

A study led by Daniel J. Cziczo, taking measurements from four aircraft measurement campaigns, sampling regions of cirrus cloud between 2002 and 2011 over North and Central America, found that two specific kinds of ice nuclei, those from mineral dust and metallic particles are favoured, constituting the nuclei for 61% of all cirrus clouds, despite the fact that other, less favoured aerosols, are more abundant. 

The vast majority of atmospheric aerosols consist of sulfates and organic molecules. They were underrepresented as the nuclei for 14% of cirrus clouds, whilst carbon and biological material were essentially absent.


Metals found as favoured ice nuclei for 9-26% of cirrus clouds included lead, zinc, tin, copper and silver. 

Lead, in particular, has been shown, in addition to being an ice nucleus itself, to have the effect of “supercharging” pre-existing particles, making even more highly efficient nuclei.


Mineral dust is mainly composed of the oxides (SiO2, Al2O3, FeO, Fe2O3, CaO, and others) and carbonates (CaCO3, MgCO3) that constitute the Earth’s crust. 

Of central importance, is a class of ice nuclei obtained from cirrus clouds that is very difficult to distinguish from mineral dust and tends to be coupled with it by scientists. This is coal fly ash, the particles of which, like mineral dust, are very efficient CCN. One study on cirrus cloud conditions found, using Single Particle Mass Spectrometry, that 33% of the ice crystal residues were “mineral dust/fly ash”. Then they used electron microscopy to show that 20 % of the particles in this category had a high degree of sphericity which indicated that they were fly ash. Therefore, a significant quantity of “mineral dust” particles that form the ice nuclei for cirrus clouds are actually fly ash.

Ice nucleation by combustion ash particles at conditions relevant to mixed-phase clouds

That’s around 7% of cirrus clouds formed on anthropogenic fly ash.


Jet engine emissions

The next step would be to look at the contribution of aircraft to the upper atmosphere. These include sulphates, soot and metal particles in addition to carbon dioxide, water vapor, nitrogen oxides (NOx), carbon monoxide, and hydrocarbons such as methane.


Soot and sulphates, the usual suspects for contrail formation, which are more abundant in the atmosphere than the favoured ice nuclei, have been found to be insignificant contributors to cirrus cloud formation.

Logic suggests that the metal particles in the jet exhaust are, in alignment with Cziczo’s findings,  major players in contrail formation. These particles originate from the ash residue of jet fuel combustion. Engine erosion also plays a role but if we are looking for an intentional addition of metal particulates, then jet fuel additives is the first line of inquiry.

Although the fuel additives contain trade secret substances, we know that these include Aluminium and Barium.

Lead, which was found by Cziczo to be among the most common ice nucleating agents found in cirrus clouds, is still used in light aviation fuel in the form of Tetraethyl lead (TEL). TEL was also added to automotive fuel until regulation in the 1980’s. The lead from light aircraft along with increasing emissions from coal combustion and smelting are thought by Cziczo to be the dominant sources in the atmosphere. 

Although lead is not supposed to be an additive in commercial jet fuel, this study analysing TF-30 jet engine exhaust from JP-5, found lead levels 50% above the control.


Metal Composition of Jet Engine Exhaust

Chemical analyses of jet engine exhaust samples indicate that the

exhaust contains heavy metals. Exhaust samples collected at the jet

engine test cell showed substantial increases in metal concentrations above the control sample, as shown in Figure 5. Zinc, copper, and beryllium were all observed at levels 100 percent above the control. Lead levels were 50 percent above the control; cobalt and

vanadium were observed at less dramatically increased levels—25

and 28.6 percent, respectively.” Emphasis mine


Lead iodide, along with Silver iodide, were the ice nuclei that were determined in the mid-40s to be the most effective candidates for artificial cloud seeding. Lead oxides and mixtures with ammonium iodide were later found to be similar, if not better, ice nuclei. Later still, it was found that pure lead-containing materials were not required for ice nucleation; instead, lead need only be present as a surface inclusion on an inert core.


Despite the switch to unleaded fuel down below, and supposedly in jet fuel, it appears that jet fuel emissions do in fact contain lead, along with other heavy metals. 


Certainly, jet fuel exhaust emits about 0.01% ash, the US EPA standard being 0.02% ash. About 0.45kg of ash is produced for every 450kg of fuel burned. This works out as around 254,276 x 1013 submicron particles emitted per metre of flight. Those particles entrain water vapour and grow rapidly to ice crystal sizes that are visible as contrails. As they spread out and  (given enough atmospheric water vapour) grow in size, they form aviation induced cirrus clouds as in our example above.

The Seven Percent Solution


We have eliminated jet engine water, soot and sulphates as the major suspects for contrail and aviation induced cloud formation and focused our attention on the combustion ash particles produced in jet fuel exhaust. There remains a degree of uncertainty as to the origin of the numerous lead particulates found in the upper troposphere. Although used in the fuel of light aircraft, lead is not officially an additive in the fuel of commercial jet engines, despite being found in jet exhaust. Lead is, however, a component of coal fly ash, which, as you will remember, is an extremely efficient ice nucleator and is categorised together with mineral dust, the aerosol of choice for cirrus clouds.

Coal fly ash has been found to comprise the ice nulclei for 7% of cirrus clouds. Recall that cirrus clouds themselves, cover around 30% of the globe. While Cziczo surmises that this coal fly ash is from increased emissions of coal combustion arriving in the upper troposphere, we are faced with the claim that, since the clean air regulations passed in the 1970s, such emissions have presumably been significantly reduced. In fact, it is estimated that around 90% of coal fly ash is captured by electrostatic precipitators and other devices. The quantities of these ash particles that are emitted to the atmosphere are said to be due to inefficiencies with the precipitators and other collection systems, transportation and storage of the collected fly ash.

Yet, whilst emissions have been reduced, cirrus cloud cover associated with air traffic has potentially increased by 8% over the last 4 decades, resulting in a global forcing of 1.6 W m2. This 8% is very close to the 7% of cirrus clouds that have coal fly ash as the ice nuclei. 

Recall from part 3 where it was revealed that higher clouds had increased globally in the region 60°N to 60°S over this period whilst the lower clouds had decreased. An increase in high, warming clouds and a decrease in low, cooling clouds. Could this be connected with the reduction in emissions from coal combustion, and thus coal fly ash, in the lower troposphere and an emplacement of the same aerosol by means of aircraft into the upper troposphere?


This suggests that if an aerosol has been deliberately introduced into the upper atmosphere by means of aircraft for the purposes of climate modification, then the balance of probability swings towards coal fly ash being such an aerosol. This would, of course, supplement the ash produced by the additives in the jet fuel. The very fact that coal fly ash is difficult to distinguish (but not impossible) from mineral dust would support the notion of a clandestine aerosol campaign.

“When you have eliminated the impossible, whatever remains, however improbable, must be the truth.” Sherlock Holmes





Summary and Conclusions

  • Contrails and aviation-induced clouds, as the name implies, come into being as a result of aircraft.

  • Water produced by combustion of jet fuel is relatively insignificant compared with atmospheric water in the formation of contrails and aviation-induced clouds.

  • Atmospheric aerosols, of the kind that readily entrain ice, are very rare.

  • As a consequence of this, contrails and aviation-induced clouds originate from aerosols emitted from aircraft.

  • Given that, a potential 8% global increase in cirrus cloud cover over 4 decades, resulting in a global forcing of 1.6 W m2, has been correlated with air traffic, it could well be that international aviation has contributed a vast number of such aerosols to the upper troposphere.

  • This aerosol fingerprint is observed in the record of upper atmospheric humidity, revealing a decline, counter to a CO2 induced warming but in line with aerosol induced cirrus cloud formation entraining water from the surrounding atmosphere.

  • Soot and sulphates, the usual suspects for contrail formation, although abundant in the atmosphere, have been found to be relatively insignificant contributors to cirrus cloud formation.

  • Two specific kinds of ice nuclei, those from mineral dust and metallic particles are favoured, constituting the nuclei for 61% of all cirrus clouds, despite the fact that other, less favoured aerosols, are more abundant. 

  • Metallic particles originating from the ash residue of jet fuel combustion are candidates for the aerosols of choice in contrail formation.

  • It has been established that around 7% of cirrus clouds may be formed on anthropogenic coal fly ash particles which are usually classified together with mineral dust. This figure of 7% matches well with the 8% increase in cirrus cloud cover over 4 decades correlated with air traffic.

  • Lead, among the most common ice nucleating agents found in cirrus clouds, is still used in light aviation fuel in the form of Tetraethyl lead (TEL). It is not officially used in commercial jet fuel but has been detected in jet exhaust particulates.

  • Lead is also a common component of coal fly ash.

  • The correlation between air traffic and the 8% rise in cirrus cloud cover taken together with the 7% of cirrus clouds formed on coal fly ash, including lead, the most effective candidate for cloud seeding but not used officially in commercial jet fuel, suggests that fly ash may be the aerosol of choice for deliberate deployment.

  • This is further supported by the correlation between regulation of coal fly ash emissions and the reduction in lower cloud cover taken together with the increase in upper cirrus cloud cover matched with coal fly ash particulates. 

  • This suggests that fly ash has been removed from the lower atmosphere and emplaced in the upper atmosphere for the purposes of warming the climate.



It is a matter of public record that during debates on cloud seeding in 1954, it was argued that the most promising method was coke furnaces and not aircraft. Coal fly ash was evidently recognised as an excellent and cost effective cloud condensation nuclei for lower, cumulus clouds. 

For the purposes of cirrus cloud overseeding, aircraft would be required to deploy coal fly ash into the upper atmosphere as both a cost effective and clandestine means of climate modification.

In part 9, we shall see how the research carried out by prominent geologist, Dr Marvin Herndon, and other concerned scientists, provide the basis for the argument set forth here.