Molto spesso I find phrases given to the effect that contrails created by aircraft have increased exponentially, filling the sky, which now appear clearly too profusely, suggesting - or explicitly saying - that in an unspecified past were not so '. Obviously, such claims are never accompanied by objective data or evidence (I 'by obvious considerations on change of entity' in air traffic over time). So, as you can 'make an idea of \u200b\u200bthe situation?
As a first contribution to tackling this question, report a 1970 publication: B. Wallace Murcray,
"On the Possibility of weather modification by aircraft contrails" (full reference: MURCRAY, W.B., 1970: ON THE POSSIBILITY OF WEATHER MODIFICATION BY AIRCRAFT CONTRAILS. Mon. Wea. Rev., 98, 745–748. )
Riporto il paragrafo introduttivo di questo studio:
Aircraft contrails first attracted public attention during
World War II; but as air traffic has built up to its present
level, they have come to be accepted as part of the environment.
Even during World War II, it was difficult to watch
the cloud cover laid down by a large bomber formation
without wondering what it might be doing to the weather;
at present, there is widespread belief among the general
public and some feeling among scientists (Fletcher 1969,
Reinking 1968, Livingston 1969, and Schaefer 1969) that
contrails are increasing cloudiness, if nothing more, in
some regions. The writer himself has seen instances in
which a single contrail seemed to grow until it became an
overcast covering the whole sky. If the contrail were indeed
responsible, which is by no means certain, this would
constitute definite proof that contrails are capable of a
significant effect on local weather, and even possibly on
global climate, if such occurrences are widespread and
frequent. It seems worthwhile, in view of all this, to
consider quantitatively whether or not there is reason to
believe contrails are capable of exerting a significant influence
on weather.
Even without retrieving other parts of the document, that 'emerging and' quite pronounced. Contrails are certainly not something that 'suddenly appeared in recent years. The author shows how since the Second World War had something particularly eye-catching, so then it becomes something "to be accepted as part of the environment", an event that is so 'normal to be perceived as an integral part of the environment that we surroundings. Recalling that the writing and 'in 1970, it is clear that the trails are a phenomenon present, famous and known for some time, or rather, when and' developed the technology of aviation. Not only that: it is also reported that contrails can essere persistenti, ed evolversi fino a diventare vere e proprie nuvole. Questa osservazione e' molto rilevante, dato che un'altra accusa che ho spesso incontrato riguarda il fatto che le scie di "oggi" restino visibili a lungo e che si espandano progressivamente, dunque per questo non siano normali scie di condensazione. In realta', anche per questo punto e' noto da tempo, e da tempo studiato, il fatto che le contrails possano essere persistenti, ed evolversi allargandosi fino a non essere riconoscibili rispetto ad altre normali nuvole.
Non solo: questi elementi fanno modo che sin dai tempi di questo scritto ci sia posti il dubbio dell'impatto ambientale del traffico aereo e delle scie di condensazione che creano; quello che in maniera intuitiva and little depth is observed from Murcray, will be 'the subject of many investigations in the future. In fact there are many studies since the early '90s, I found (I will report 'depth in the future) and deal with the impact of contrails on clouds, and thus the possible contribution to climate change, particularly how they can participate in the so-called Greenhouse Effect.
conclusion, in summary: those who say that the wakes formed by the planes are a recent phenomenon, or is otherwise relevant become a phenomenon recently, makes a mistake, those who argue that the contrail must necessarily be small and vanish soon time (otherwise you are expected to be something "different"), he lies.
