Chemtrails, contrails and conspiracy theories

I've become aware of a conspiracy theory that geoengineering is already being secretly implemeted. The theory goes that governments around the globe are using aeroplanes to spray toxic "chemtrails" across the sky.

Chemtrails (chemical trails) supposedly differ from "contrails" (condensation trails) by lingering in the sky for hours longer than contrails, which vanish after a few seconds. There are several forums in which people have given accounts and posted alleged videos and photos of chemtrails.

They range from the paranoid to the hysterical.

So far I've seen no credible evidence for chemtrails (everyone knows how easily photographs and videos can be doctored, and I noticed that one repeat video uploader had a YouTube profile image reading "9/11 WAS AN INSIDE JOB" - serial conspiracy theorist ahoy?). But this conspiracy theory has piqued my interest nonetheless. Bear with me whilst I explain.  

Whether or not the theory is a direct response to the SPICE project in particular, I can't be certain. But it does seem to originate in the similarities between proposed methods for stratospheric particle injection put forward for solar radiation management, and the production of chemtrails. The conspiracists actually describe the chemtrails as geoengineering so they have certainly made a link between the two.

Figure 1. Alleged chemtrails. Source: Geoengineering Watch

The theory is so widespread that David Keith, leading geoengineering scientist at Harvard University, has published a response including two fundamental reasons why it should be taken with a pinch of salt: lack of evidence supporting the theory and lack of motivation for governments to do such a thing.

Whether or not a paranoid conspiracy theorist would be convinced by Keith is debateable, especially given the fact that he himself is a prominent geoengineer who many of the consiracists seem to suspect is involved.

But I'm not getting involved with the conspiracy theory itself.

What struck me is that this theory has a substantial following. Whether or not it's correct doesn't change the fact that a signifcant amount of people here are actually scared of the possibility of a technology that could spray chemicals into the atmosphere and modify the weather.

That fear does resonate with me: it raises questions in my head about how ethical it is to develop a technology of which peope are this fearful, especially given that a technology as large-scale and far-reaching as stratospheric particle injection could ultimately affect anyone on the planet.

It also highlights how crucial total transparency is in scientific research to avoid public paranoia. Making information as open and accessible as possible in the first place is surely the easiest way to prevent people speculating on what may or may not be happening.