The part of the debate that show this is:
Dane: what is necessary for that cloud to form though Mick? Particulate matter. Right?
Mick: Yes particulate matter, but ...
Dane: ... it can't form without particulate matter can it?
Mick: ... the air is full of particulate matter. Everywhere, even in the clouds or not in the clouds, there's particulate matter everywhere, there's no shortage of particulate matter. The stuff that comes out of the black of the plane helps the contrails to form a little bit, but if it was perfectly clean, if it was just spraying water out of the back of the plane, you'd still get a contrail, because there's particulates in the atmosphere.
But the point we were talking about here is that there's a gap in a contrail, now, all the contrail is doing is revealing where in the sky the areas of humidity are. So if there are area of humidity that are shaped like clouds, which have very sharp edges, you've see cumulus clouds with incredibly sharp edges, why wouldn't a trail flying, a plane flying through area of humidity start and stop at exactly where those boundaries are? If it was flying through...
Dane: ... the turbulence alone around a passing aircraft could never make possible what you describe, it is absolutely impossible. And if you describe, what you described is true Mick, then how come as the same time we see an aircraft leaving a trail from horizon to horizon, we can spot, and we have on film, aircrafts flying at the same approximate altitude, leaving virtually nothing. Why is that? How is that explained?
Mick: because, it's the same approximate altitude, it only takes a few hundred feet in difference for you to be in a different layer of the atmosphere. And it can be very different humidity. There have been tests done in Germany where they have two planes flying side by side. One of them leaves a trail, and the other one doesn't leave a tail, because they have slightly different engines.
There are two point:
1. Mick West claim that: " The stuff that comes out of the black of the plane helps the contrails to form a little bit, but if it was perfectly clean, if it was just spraying water out of the back of the plane, you'd still get a contrail, because there's particulates in the atmosphere"
2. Mick West claim that: " There have been tests done in Germany where they have two planes flying side by side. One of them leaves a trail, and the other one doesn't leave a tail, because they have slightly different engines"
1st claim clearly wrong. The particulate exist because of jet plane and more particulate in fuel clearly change the behaviour of contrails.
CONTRAIL AND CIRRUS CLOUD AVOIDANCE , Frank Noppel, Riti Singh - Cranfield University, Bedfordshire, United Kingdom, - Mark Taylor - Rolls-Royce plc, Derby, United Kingdom.
Aviation has been identified as contributor to anthropogenic changes in the Earth’s radiation budget. In particular this is due to the emission of greenhouse gases, soot, aerosols, and the formation of contrails and aviation induced cirrus clouds. Linear persistent contrails occur in an ice supersaturated atmosphere if the Schmidt Appelman criterion is satisfied (1). Cirrus clouds can evolve from spreading persistent contrails known as primary cirrus or contrail cirrus (2). Secondary cirrus occur due to locally increased soot and aerosol concentration, which might lead to theformation of cirrus clouds that would not form in the absence of air traffic (3; 4; 5). An indirect climate forcing of aircraft emissions is possible by changing particle size and ice particle number density of natural cirrus clouds (6).
Aviation induced pollutants have been identified and assessed in terms of radiative forcing by the Intergovernmental Panel on Climate Change. Radiative forcing is a metric where the expected steady state equilibrium change in terms of global mean surface temperature is related linearly to the observed radiative forcing of a certain perturbation. Linear persistent contrails and aviation induced cirrus clouds were identified as main contributors to the overall aviation induced radiative forcing. It is estimated that linear persistent contrails contribute approximately 20% to the total aviation induced radiative forcing (7). This estimate considers a year 2000 scenario where cirrus clouds are excluded. Aviation induced cirrus clouds have the potential to cause a radiative forcing which exceeds the radiative forcing of all other emissions due to air traffic combined. Annually and globally averaged total contrail cover and the associated radiative forcing is expected to quadruple during the next decades due to the increase in air traffic (8).
Depending on the allocated importance of the radiative forcing due to persistent contrails and cirrus clouds relative to that of other aircraft emissions, it might occur that the avoidance of persistent contrails and cirrus clouds becomes the most important and pressing issue to be addressed in the future.
The article mention that the increase of particle in atmosphere happen because of air travel. Also read the two next reference too. If different sulfur content in the fuel can produce different trails results, then the effect of existing particle in the atmosphere should be small compared to the effect of particle from the exhaust. The correct claim would be: "The stuff that comes out of the back of the plane helps the contrails to form a lot"
Emissions trading in international civil aviation by Öko-Institut e.V. Institute for Applied Ecology
As a result of aviation, emissions are expelled into the global atmosphere that contribute to climate change and the destruction of the ozone layer. Emissions and expelled particulates alter the concentration of greenhouse gases – carbon dioxide (CO2), ozone (O3) and methane (CH4). They also trigger off the formation of contrails and can encourage the occurrence of cirrus clouds. All of this contributes to climate change (IPCC 1999).
2nd claim may be correct, but different sulfur / particle content can cause such difference too, this also deny the 1st claim:
Contrails: What’s Left Behind Is Bad News, By Nick Onkow, March 4, 2006
There are several methods that can be explored that will help reduce the role that contrails play in global warming. The easiest way to avoid this global warming through contrail cirrus clouds is to have jets fly at different altitudes. Flying higher than the typical 30,000 to 40,000 feet would usually stop contrails from forming, as would flying lower. another option might be to increase the emission standards of jet engines and with that only insure airplanes with the newer, cleaner engines. Tests were performed with a NASA jet aircraft examining the effect of sulfur levels in jet fuel exhaust. During the airborne test one engine was run on normal jet fuel and the other engine was run on fuel that emitted exhaust with a lower sulfur content. The high sulfur engine, representing most jet engines on modern commercial aircraft, produced a contrail that lasted through a larger range of temperatures and formed faster out of the engine. The low sulfur engine did the opposite. This condensation nuclei is the tiny matter that gives water vapor the ability to form. The International Civil Aviation Organization is in favor of making polluting, obsolete aircraft uninsurable. While this option would not completely eliminate contrails, it would narrow the window of conditions needed to form them, making them less common.”
I wish both Dane Wigington and Mick West can use reference from scientific community. Especially because both have many follower.