The Contrail Chicken and Egg and how a Conspiracy theory was born or why worry about CO2 when you have planes and ships and sulphur? By Dr Chris Barnes Bangor Scientific and Educational Consultants. June 2013.


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New types of contrail and cloud and associated optical phenomena   which have in the USA, UK and other parts of the world recently become far more prevalent are discussed. The site of persistent spreading contrails and some   aircraft  apparently leaving horizon to horizon contrails which seem to ‘burn’ into the sky or other cloud has led some to question if stratospheric geo-engineering has already and perhaps illegally commenced?  The present author doubts that this is the case but seeks to clarify what is being seen in terms of cloud and aircraft microphysics and such issues for example as clear air seeding and inadvertent weather modification are also discussed. The history of persistent contrails and changes to contrails is discussed. The critical paper on non-linear sulphate aerosol aircraft emission is discussed. Modes of negative climate forcing are discussed. The hypothetical question is posed could ordinary aircraft at cruise altitude already be engineering the climate of Wales accidentally by aerosol entrainment or intentionally? The relevance of ship tracks and ship fuel is also entered into the equation. Three distinct types of climate forcing are identified in association with persistent contrails over North Wales.  Such forcing on occasions seems easily to be able to outweigh CO2 effects. It is possible there are three different types of persistent contrail responsible either by different entrainment of different aerosols or because of formation under different climactic and wind shear conditions.       Contrails also seem to regulate rainfall in a complex and not understood manner with often cubic relationships between monthly anomaly and number of outbreaks. Rare and unusual optical phenomena seem to be more associated with the ice of contrail cirrus than with natural cirrus, presumably due to crystal size and geometry. With so much happening in our skies there is no wonder weird and wonderful conspiracy theories have arisen in relation to aircraft emissions around the world.

However that the aerosol types associated with persistent contrails always arise directly from the planes which leave the contrails are associated cannot yet properly be proven. Persistent contrails may form by an entrainment of other anthropogenic or natural aerosols in their vicinity.  The anthropogenic component can be as a result of emissions from other aircraft, the same aircraft on circular flight paths or distinctly different sources.  However, the purposeful use of experimental changes of aircraft and ship fuel cannot be ruled out or in. Unintentional changes based purely on availability or supplier of fuel could lead to similar variations in sulphate and black carbon emission which could, potentially, bring about the changes observed. What does logically seem very probable and perhaps dangerous is that engineering our climate and weather might be far easier than we had once thought?  The danger is have weather wars already commenced?



Since around the turn of the present century the World’s skies have changed dramatically (1). Even NASA have information web pages on these changes (2). Yet strangely amongst the ranks of ‘Joe Public’ only those of us who are ‘in touch with nature’ to coin a somewhat corny phrase or those of us who have hobbies or jobs where we need to look skyward may even have noticed.


Complete new families of contrails and clouds have been born. Hitherto rare clouds and rare optical phenomena such as day glows, haloes, circum-zenith arcs iridescence and the like have become far more common.


Besides the linear decaying contrail of old, education sites have introduced the public to the linear persistent contrail, the spreading contrail, the persistent spreading contrail and contrail cirrus (2) also sometimes referred to as cirrus aviaticus (3). Other new cloud types include Undulatus Asperatus (agitated waves) (below) and in the UK clouds like lenticular and Kelvin Helmoltz are also been seen more often


Is there any wonder then that amongst certain groups various conspiracy theories have sprung up, particularly on the internet, to suggest that our skies are being chemically and even electronically manipulated, or that geo-engineering of our weather and climate has already somehow illegally commenced.


According to the experimental observations of the present author and what is currently available in the scientific literature the truth of the matter is probably more like that our weather and climate have been inadvertently altered since human kind first discovered fire and agriculture but that even more profound changes have happened since the industrial revolution and in particularly with the discovery of and moreover recent explosions in jet aviation (4) and bulk container ship transport (5).


The present author has made an extremely careful and almost exhaustive review of the available climate data and literature and this would certainly seem to confirm that the biggest changes to our climate seem to have happened since jet air travel and that reported slowing or halting of global warming seems to have happened since the appearance of the above named exotic contrails and clouds in our skies over about the last decade and a half or so. Indeed the present author has also reported on this elsewhere (6).


There are several possible reasons for this not all associated with transport and some probably run concurrently:


1.      CO2 may not be having as large an effect as previously presumed (6, 7)

2.      Anthropogenic and natural sulphate aerosols are more profound than previously assumed and are having a larger negative climate forcing effect than previously presumed (8)

3.      Some of the new cloud types have ice crystals which scatter and reflect sunlight as to produce a negative climate forcing/ dimming effect and also alter diurnal daily temperature range (9, 10)

4.      Weaker solar cycles and GRB plays a strong part (11, 12)

5.      Cooling due to increasing numbers of ship tracks (13-17)

6.      Some combination of all or any of the above 1-4

7.      Two way effects of AGW (acoustic gravity waves need to be taken into account ) (6)

8.      Infrasound and other effects from wind turbines may need to be taken into account (6, 18, 19)

9.      Perturbation of the ionosphere by ionospheric heaters, although subtle, may also cause effect via ozone for example (20)

10.  Stratospheric ozone levels (21)


The list is perhaps by no means exhaustive and the items in the list clearly have the potential for incredibly complex and multivariate interplay.  

Potentially, however, in the clear sky situation features 1, 2 and 4 could still predominate. There is a large body of evidence in the literature to suggest that aviation although only responsible for some 3 % of the world’s CO2 emissions is responsible for a far larger degree of climate change (22).

It is proposed here that whereas previously the effects of aviation have been inadvertent, science is now at a point wherein there is potentially sufficient knowledge and understanding to engineer climate and weather, if need be, by using nothing other than ships and normal passenger aircraft with specifically chosen fuel sulphur contents in addition to various cloud seeding techniques to compensate for contrail effects on the hydrological cycle.


Some History

Some have cited recent outbreaks of persistent contrails around the world as evidential of some new and clandestine alchemy in our skies (23). However they are not a new phenomenon. They often occur wherever and whenever there is particularly heavy air traffic. Indeed they were first recognised across the English Channel in WW2, as was their effect on local weather conditions (24). It would seem therefore there is some threshold as more and more planes use the same or similar airspace given the right level of relative humidity and ice super saturation. As more planes follow flight paths, they introduce more vapour into the already supersaturated air, and attract more water vapour from the surrounding air, making the ice crystals increase in size and the contrail to become thicker. It’s almost the exact same way clouds are formed, and from a meteorological aspect, we can regard contrails as human- made cirrus cloud (meaning they are physically similar to normal clouds) if they are observed persist for at least 30 minutes. The precise ice crystal shapes in sizes in contrail cirrus and the precise chemistry might be slightly different from natural cirrus (9, 10).


Since WW2 it would be some time before aircraft flew on any particular route with anything like approaching the same density per hour. Perhaps we are just arriving at that sort of density on some modern passenger routes. Persistent contrails can also form when the same aircraft flies back on itself in a tight circular path (25).


But why are there are now so many weird and wonderful cloud shapes and types in our skies, as indeed documented by NASA (2). The present author has explained this elsewhere (6), but basically, to recap, a chance re-design of turbofan engines over the past two or three decades means that now nearly all the jet passenger aircraft in our skies are of the high bypass ratio type (26) which means cooler exhaust emissions and hence more chance of visible contrails and of course along with contrails comes the emission of carbon dioxide, black carbon, PAH and sulphate aerosol. It has been postulated that although this carbon dioxide is only some 3% of the world’s emission due to its injection into the UTLS it could potentially have far more climate warming ability (22). Why then do contrails now appear to be cooling the planet or at least still appearing in the skies of a cooling planet? One possibility is ice crystal size. Although contrails often transform into cirrus clouds, the natural variety of which have a climate warming effect. Some contrail cirrus does the opposite (27,28).



The key scientific paper for climate change

Some countries have introduced clean air acts and are attempting to make less sulphur emissions, for example in order to reduce acid rain. This has possibly caused some well-known climate scientists to release confusing information regarding the state of sulphate aerosol in the UTLS.


For a truer picture we need to look critically at sulphate aerosol from aircraft emissions as this is the clue to countering global warming. In the opinion of the present author the one critical paper and the indeed one that often seems to be overlooked is that of Miake-Lye (1988) (29) whose abstract states the following: ‘Volatile and nonvolatile aerosols were measured in the wake of a B757 airliner in flight, in concert with measurements of gaseous SOx and CO2 emissions, while the airplane was burning fuel with a sulfur content of either 72 parts per million by mass (ppmm) or 676 ppmm. The volatile aerosol number density exceeded that of the nonvolatile for both fuels and, while the nonvolatile (soot) component was largely insensitive to the fuel sulfur content, the volatile component depleted the gas-phase sulfur species with a condensed fraction that increased from 6% (low S) to 31% (high S). The large proportion of SOx in the aerosol phase and its nonlinear dependence on fuel sulfur content cannot be explained by known combustion mechanisms and has the potential for significant environmental effects.’


We know now that the significant environmental effect of sulphate aerosol is to produce global cooling or negative climate forcing and has previously been stated as being easily able to completely offset greenhouse gas forcing, particularly   in summer in the United Sates and parts of Europe, see 30.     JT Kiehl, BP Briegleb - Science, 1993 (30). Soot or black carbon is known to cause positive forcing (ref) but we note here that according to Miake-Lye the soot component was insensitive to sulphur concentration, so the sulphate aerosol cooling effect would always outweigh the soot positive effect. Besides which the soot is essential or at the very least useful for ice nucleation in contrails and given ice crystals of appropriate size and shape these too will cool rather than warm, this happens for cirrus clouds with a large number (>107 m−3) of small (mean maximum dimension <30 μm) ice crystals and cirrus clouds with bi-modal crystal size distribution and large particle size for the second maximum peak, see Zhang et al . (1999( (31).


Is there evidence of ‘clandestine aerial experimentation’?

Can experiments be done to validate the existence of a recent new or stronger negative climate driver and would some clandestine whole sky scientific experiments be very wrong if they involved nothing other than aircraft flying on different types of fuel or with and without contrail avoidance systems provided nothing really harmful was used and is there evidence of this?


At least three pieces of work appear in the literature documenting real sky experimentation. The most obvious of which is the so called SUCCESS experiment (32,33). Clearly the Miake-Lye experiment was done in a real sky somewhere by its own volition that the B757 was an airliner in flight (31), as was SUCCESS.

Haywood et al  2009 comments on the  surprising and staggering effect of spreading of  contrails over the UK formed by the circular flight  an aerial observation platform (AWACS) (34). These have all been ‘one off’ experiments.   

Good science requires reproducibility and to test this one requires multiple experiments. Imagine the scenario of flying an entire fleet of passenger aircraft for a month or a year on sulphur rich fuel and then switching to sulphur weak fuel and analysing ground based and satellite based weather and climatic data. Alternatively, imagine the scenario of flying just a few aircraft with very sulphur rich or soot rich exhaust emissions into already crowded air -lanes. These would be two possible way to properly evaluate the effect observed by Miake –Lye. The probability of contrail formation would be more or less the same each time, the amount of soot and CO2 and even contrails are ones experimental constants. The amount of sulphate aerosol is one’s experimental variable. Only by doing experiments like this could meteorology and climate science really advance. This is not conspiracy; this is certainly not chemtrails to coin someone else’s phrase. It is or would be or ought to be or has been, whatever the case may be, just good, practical, science.


On the other hand contrail avoidance systems are also available now. Thus if one wanted to evaluate the effect of contrails formed by a fixed fuel composition, large numbers of flights could be made with and without the use of contrail avoidance systems. A member of the lay public or even an experimental scientist from another discipline such as the present author, without insider knowledge of NATS or the Met Office, would not know if the effects of such systems were being evaluated. One could perhaps assume that they have or are being so? If not, why not?

Alternatively one could assume that such systems may be phased in on the basis of ‘recommended good practice’ (35) but perhaps without proper regard or evaluation of a climate system that had begun to stabilise without them? Statistically one might perhaps expect roughly even numbers of persistent contrail outbreaks on a month on month or year on year basis but in fact under the air corridor which passes over the North Wales coast this has not been the case. There were huge numbers of persistent contrail outbreaks in the mid 2000’s but recently there have been far fewer. This could be indicative of contrail avoidance systems now in more frequent use, alternatively it could be due to lowered humidity associated with massive climate cooling, see Doran et al (36).



It is impossible to conduct a worldwide experiment to test the above hypothesis as the author simply does not have the means or access to all of the data. However, a fairly detailed set of experiments can be constructed for the Welsh climate anomaly using readily available Met Office Data. All that is needed is to count persistent contrails and correlate the number of events with the available temperature data. The author has his own historic records of persistent contrails going back to about 2004 and first noticed a substantial growth of the phenomenon in North Wales as early as 2001. Sadly what was not recorded was the time of day that all the outbreaks prevailed. However, the author does recall that some were early morning and others appeared to be laid down at about 8-9 pm in the evening. It is hoped to report on these aspects in more detail at a later date because contrails are known to influence daily temperature range, see Travis et al 2002  (37) and Dai et al 1999 (38) and crucial in this is diurnal radiation budget which depends of course on day/night cloudiness levels.


Either way the observations of the author remain relevant because if persistent contrails do not appear to behave the same year on year or month on month this is viewed by the present author as evidence of the presence of additional or differing climate drivers.





The results above are truly somewhat perplexing. It appears that aviation, viz a viz observed persistent contrails across North Wales may have had substantially different effects in different years. One can only reconcile this, particularly the 2005 result by assuming that additional climate drivers are at work. For the year 2005 in particular there would appear to be a negative climate driver related to the incidence of contrails. It is perfectly reasonable to assume that either the ice crystal sizes in contrails that year over North Wales were such that they brought about dimming/cooling (such ideas were first discussed by Liou (1986) (39) and later by Sassen 1997 (40) or alternatively that high sulphur fuel was in use by air fleets or that more sulphate aerosol from some other source was available for entrainment. It should be noted that Khvorostyanov and Sassesn (41) have noted that under certain conditions contrail cirrus can cause surface cooling.

In 2006 there were some thirty extra days with instances of persistent contrails visible over North Wales and the situation with regard to their effect on the monthly temperature anomaly appears to be more or less exactly reversed.


On the other hand in 2007 there were far fewer persistent contrails as a whole, so possibly contrail avoidance technology featured more heavily. The average monthly temperature anomaly for about three cases of persistent contrails per month is almost constant. Very interestingly however if this contrail frequency is normalised to levels in the previous two years the monthly temperature anomaly would have been almost three times higher and in the region of +4C!


Taking the most prevalent cases of persistent contrails over these three years is also interesting.  Maximum numbers of such contrails occurred mainly in the spring and summer months with the exception of January 2006. Except in the single observation for January 2006 this result is in direct contradiction to that of Radel and Shine for Reading in the UK (42).  It also seems to contradict the work of Meyer et al 2002 (43). Further, normalising as above yields a staggering 7.2C positive anomaly. It should, perhaps be noted that Reading is more in-land than North Wales and in the latter there could be more of a contribution of sea sulphate aerosol and ship track effect.   It would appear that in months when contrails become very persistent and very prevalent, warming dominates over cooling.  This could be either because the contrails were formed at night and trap heat or because they were formed earlier and have persisted all night.  


Global cloudiness is predicted to increase as a result of increased humidity from climate warming. Persistent contrails too are clouds recently described a ‘man made’, see Palikonda et al 2002   (44). It should thus be a relatively simple exercise to test this hypothesis simply by adding up the total temperature anomaly for each year concerned and plotting against contrail numbers. The plot is shown in figure 2 below:


Figure 2

 Although the correlation is not good, the result, nevertheless, appears exactly contrary to what is expected. It rather suggests that contrail numbers are controlling temperature rather than temperature controlling contrail numbers. Further it suggests that on average a negative climate forcing dominates by or in association with the presence of persistent contrails over North Wales.  Clearly there is a switch over from positive to negative forcing perhaps when contrails do not persist all night or perhaps there are other factors such as different types of aerosol or different types of climatic conditions at work.  

The author's hypothesis here is that there could be both an ice crystal effect and an aerosol effect. If one assumes that aerosols are still present across each entire month of observation irrespective of contrail persistence and also if one makes the assumption that the two main types of aerosol present are black carbon and sulphate one can better evaluate the effects of the contrails on the basis of background aerosol. This ought to be possible by looking directly at the Met Office monthly figures since rainfall anomaly in addition to temperature anomaly figures are available. The anomaly comparison used here is always with the mean 1966-1990 figures because these are the most historic available and are figures based on a period when not so many exotic cloud types were observable.


Based on the assumption that background high sulphate aerosol would lower surface temperature and reduce rainfall  it has been possible to explore the effect of persistent contrails in the presence of such, see figure 3.

Figure 3



Only data from 2005 and 2006 has been used to generate figure 3 since it is suspected that Black Carbon dominance was occurring in 2007 and/or that more persistent contrails were formed at night or persisted all night.  What seems astounding is just how much negative local climate forcing there appears to be given this is a two year period in which CO2 was continuing to rise virtually unchecked. The most obvious conclusion is that it may be the same aircraft which produced the contrails which injected the aerosol, however without ‘insider’ information this is impossible to prove.    The other alternative is that the sulphate aerosol arrived from other natural and anthropogenic sources and somehow worked symbiotically entraining with the persistent contrails perhaps causing ice crystal nucleation to give crystals of appropriate size and shape to enhance ground cooling.


There were also several occasions with persistent contrails, particularly during 2006 and 2007 when it was suspected that there was Black Carbon aerosol dominance and/or night-time formation or all night persistence.  Black carbon aerosol has been documented to cause severe positive climate forcing, see Jacobson 2001 (45) and can either reduce or enhance rainfall, see Menon et al 2002 (46) and Rosenfeld et al 2008 (47).  It can come from ground level anthropogenic sources as well as aircraft. It was decided to see if there were any months in which the rainfall anomaly was suppressed and the temperature anomaly was increased in the presence of persistent contrails. The author has observed optical haloes, day glows and cloud edge effects associated with some persistent contrails and contrail cirrus which appeared to have a different optical spectra from those of their sulphur rich cousins. The author has also in several occasions over North Wales seen scud like clouds which appear reminiscent of the iron oxide clouds he saw in polluted Sheffield as a boy when the coal and steel industries were in full swing. At present he can offer no explanation for their presence. The result for the persistent contrails with suspected black carbon dominance shown is shown below in figure 4. It should be noted that some of the effect may also come from all night persistence, particularly in the summer months. 4


Just as with the sulphate enhanced trails, the magnitude of the anomaly increases with the number of instances of persisting contrails. Once again a most obvious conclusion would be that the aircraft which produced the contrails were also the source of the aerosols but the alternative conclusion is a symbiotic effect as previously detailed. Living in a coastal area away from industrial sources if the black carbon is external to the aircraft it must have been lofted some considerable distance? Alternatively ship emissions are a possibly although this is not documented in such a context?


Black carbon aerosol has been documented to cause enhanced rainfall as well as depleted rainfall (46, 47). Since there were some months in the three year period which had significant instances of persistent contrails but wherein both an increased temperature and rainfall anomaly was recorded, it was decided to examine their number density effect on both the temperature anomaly ( see figure 5) and rainfall anomaly, see figure 6 . 5


At first site based on a simple linear algorithm, persistent contrails under these conditions seem to be providing a negative climate forcing effect, however a far better fit is achieved by means of a quadratic fit, which shows that the for more than about ten instances per month warming ensues. This could possibly be because of the scavenging effect on rain bearing clouds, or due to all night persistence, see above.   It is also instructive to consider the rainfall anomaly, figure 6. 6

There is some sort of relationship with the temperature effect, figure 5. However, this appears very complex. As the number of trails increases cloud scavenging probably reduces rainfall and allows more local ground level heating. It is uncertain why rainfall again increases unless this is a fall-streak related effect. Alternatively this could be a seasonal effect or related to the climatic or frontal conditions taking into account humidity and wind shear etc. under which the trails form.  Such effects would impact ice crystal size and shape even in a relatively constant aerosol flux and would be relevant to the above observed temperature effects as well as hydrological changes.  The frontal hypothesis is discussed in more detail below.    


2013 to date for comparison

2013 to date has been one of the coldest springs on record, marked by Easterly winds and a displaced jet stream. There have of course been some Icelandic volcanic eruptions in 2010 a year leading up to 2013, sknown sources of stratospheric cooling aerosol (48, 49). Moreover such eruptions are known to fertilise phytoplankton (50) causing enhanced feedback of the concurrent negative climate forcing. Apart from in June which has seen extensive persistent contrails over North Wales, they have been mainly absent apart from a couple of outbreaks in February and March.


The cumulative effect of the contrails noted so far in 2013 appears to have been a very slight positive forcing and a very slight reduction in rainfall. This would suggest black carbon rather than sulphate dominance at present. It would also suggest that persistent contrails form more readily in North Wales in the presence of Southerly or Westerly airflow. Black carbon has been noticed both in some of the young contrails recently and in scud like clouds.  Some overnight persistence has also been noticed recently In June.  Time will tell if this too will cause enhanced warming and a recovery from the bitterly cold spring conditions. 


Effect of ships and ship tracks

Living in a westerly location in the UK, the effect of ship tracks on local climate should certainly not be forgotten. The effects of two distinct types of ship fuel has been documented by Hobbs and Garrett 2000 (51) on ship emissions and ocean generated aerosol and clouds.

 As with the air-fleet it is totally unknown to the author whether such types of climate and weather influencing experimentation has been or is presently under-way using ships and if so by whom or on whose behalf.


 Alternative hypothesis

Persistent contrails and contrail cirrus are known to form under three basic weather conditions.  These are ahead of warm and cold weather   fronts, see Kastner et al (1999) (52) and under anti-cyclonic   conditions, see Immler et al (2008) (53) wherein the optical depth can be greater. One study has showed that cirrus ice crystal sizes vary considerably ahead of and behind weather fronts, see Cohen and Barnes (1980) (54).  These differences alone may be sufficient to explain the different local climatic forcing and hydrological effects associated with persistent contrails in North Wales.   

As further evidence of the potential validity of the above hypothesis on ice crystal variations and variations in optical depth this is certainly  consistent with optical effects observed in the region.   In very hot summer weather aerodynamic contrails have been spotted in North Wales which have a pink and green appearance which later translates into the edge of contrail cirrus. According to Karcher et al, aerodynamic contrails form when air flows across the wings of subsonic aircraft in cruise. During a short adiabatic expansion phase, high supersaturations trigger burstlike homogeneous ice formation on ambient liquid aerosol particles within a wing depth. Small particles freeze first because they equilibrate most rapidly. Ambient temperature is the key determinant of nascent aerodynamic contrail properties. Only above K do they become visible (but optically thin). These temperatures are at the high end of those prevailing at tropical upper tropospheric flight levels of subsonic aircraft. In colder midlatitude conditions, aerodynamic contrails stay invisible and the very small ice particles formed quickly evaporate when exposed to small subsaturations, explaining why the formation of these contrails is rarely observed. After formation, aerodynamic contrails develop into contrail cirrus if air is supersaturated with respect to ice. This type of anthropogenic ice cloud adds to contrail cirrus derived from jet exhaust contrails and may become particularly important in the future because air traffic is projected to increase significantly in tropical and subtropical regions. Regardless of whether aerodynamically induced ice formation leads to persistent contrail cirrus, cruising aircraft may act as sources of potent heterogeneous ice nuclei by preactivating the insoluble fraction in atmospheric particle populations. Aerodynamic contrails and aerodynamically induced preactivation should therefore be studied experimentally and with global models to explore their potential to induce climate change.

Such pink and green coronas on contrail cirrus are as distinct from the red blue coronas associated with mountain wave cloud.  Sun dogs and haloes are now regularly seen in association with contrails.   At other times the contrail cirrus appears to have patches of bright red and yellow akin to distorted sun-dogs.   The above are indications of very distinct ice crystal sizes and geometries and it is well documented that depending on which there can be either negative or positive climate forcing by persistent contrails.     

Indeed as  far back as 1970 it was realised that persistent contrails could have a potentially huge effect on the earth’s radiation budget, see Kuhn (1970) (55).  Also that year Mucray realised that contrails could potentially affect/control weather to a similar   extent to that caused by traditional cloud seeding methods.


Clear Air Seeding

If we are seeing any form of geo-engineering taking place the author doubts very much that it is stratospheric injection with its attendant delivery problems.  However, a very real option to geo-engineer and one that could be inadvertently taking place a result of new aircraft designs   is that of clear air seeding first proposed by Detwiler in 1980 in which as part of his PhD thesis he made an investigation is made into the prospects for nucleating widespread ice particle clouds in clear air for the purpose of moderating surface temperature extremes and modulating atmospheric convection. Using aircraft contrails as a model, it appears that on many occasions ice particle clouds can be nucleated in clear areas of the upper troposphere that will decrease the outgoing planetary infrared radiation by perhaps twice that amount, at the earth's surface. It is possible to promote the development of much more widespread cloudiness than a typical contrail by using aircraft to release large numbers of ice nuclei so that orders of magnitude more ice particles are created per unit length of flight path than are created in "normal" contrails.  He also stated that opportunities also exist for clear-air seeding near the surface in cold climates. He also made investigations into suitable ice nuclei, synoptic weather conditions and seeding schemes are presented. The radiative properties of cirrus clouds were discussed.

Only last night 19th June 2013, the author is convinced he saw this process either inadvertently, accidently or organisationally at work over the skies of North Wales and has photographic evidence not published here to confirm it.    

At the start of this work and in other work of the present author it was and has been noted that aviation technology has changed fairly recently with the advent of the high bypass turbofan engine.   Fuel technologies  too have improved meaning cleaner fan blades and engines in general   so that perhaps  metallic particles from engines are less likely to adhere to fans and more likely to exit the aircraft. Cziczo et al (2013) have noted that formation of cirrus clouds depends on the availability of ice nuclei to begin condensation of atmospheric water vapour and that although it is known that only a small fraction of atmospheric aerosols are efficient ice nuclei, the critical ingredients that make those aerosols so effective have not been established. They have determined in situ the composition of the residual particles within cirrus crystals after the ice was sublimated. Their results demonstrate that mineral dust and metallic particles are the dominant source of residual particles, whereas sulfate and organic particles are underrepresented, and elemental carbon and biological materials are essentially absent. Further, composition analysis combined with relative humidity measurements suggests that heterogeneous freezing was the dominant formation mechanism of these clouds. 

This is interesting in that taken with fuel changes, it gives yet another route by which modern aircraft might unintentionally create more or persistent contrails. 


Conclusions and now and the future

There have been further proposals to geo-engineer the planet by direct injection of sulphate aerosol into the stratosphere, see, for example, Rasch et al (2008)(56).  There are even government committees on the topic (57. Presently this is probably not necessary, particularly as it is known that even for sulphate injected below the tropo-pause, some of it finds its way up to 3 km inside the stratosphere.


Several types of association between persistent contrail outbreaks and local climate for Wales have been shown by the present work. It would appear possibly that depending on the dominant aerosol contrails in association with ship tracks absolutely dominate the Welsh climate. It still remains uncertain whether the different types of aerosols speculated upon as in close association with the same have been injected naturally, anthropologically by the aircraft leaving the trails or separately or by a mixture of the foregoing combinations.


What seems absolutely clear is that if human kind had for whatsoever reason a legitimate and urgent need to engineer the climate using these simple aircraft and ship based methods it would seem, based on the above dramatic results, it could easily be done.


Timely work

The author feels this work is particularly timely. Some thirty of the finest minds in the UK Met Office are apparently to meet on Tuesday 18thJune to discuss Britain’s more and more extremes of and peculiar weather. It is hoped that if this work, freely published by the present author and readily available on line is found in time by those parties that it may be of some possible use to them. The author will gladly try to answer any questions or engage consultatively.


Some have talked in the past of using weather as a weapon or of weather wars (58). Some have a stated aim of using weather as a ‘force multiplier’ (59). With its manipulation possibly been as simple as changing the fuel in and routes of a number of ships and aircraft let us all hope this has not already commenced. If such manipulation is indeed being attempted by multiple parties all with different social and political agendas is there any wonder weather forecasting has become so difficult.


Recent new nano-particles have been observed  see Birmili and Wiedensohler (2000)  (60) which are present for 20 % of the time and increase SO2 concentrations by up to a factor of 7 for 80 % of that time. This observation offers an elegant possible explanation for the observed effects seen by practical sky observations of the present author.  For instance in this present study large  persistent  contrail outbreaks  are noted on 188 occasions in 3 years or some 17.5% of the time, given there are times when low cloud would prevent proper observations this compares favourably with the notion solar and gas phase influence is critical in determining both  not only the formation    and persistence of contrails but also their meteorological control and  climatic effect.       










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59. · PDF file

60.  Birmili and  Wiedensohler ( 2000)   New particle formation in the continental boundary layer: Meteorological and gas phase parameter influence, Atmospheric Science (2000) › ... › Vol 27 Issue 20