Deme

The longetivity of a contrail is determined by the atmospheric conditions. In sufficiently dry air no contrail is formed as the water introduced by the combustion isn’t enough to raise the frost point to the ambient temperature. More humidity means that the contrail may form and even persist for a while without sublimating away (Cirrus homogenitus). If the air is even more humid, the contrail may even start to grow and change shape (turning into Cirrus homomutatus). This last case is what I suspect gets the foil hats most riled up about “chemtrails”.

https://cloudatlas.wmo.int/en/explanatory-remarks-and-special-clouds-cirrus.html

No problem, it happens.

This could’ve been a quick web search on your part, but here you go:

https://www.science.org/content/article/aviation-s-dirty-secret-airplane-contrails-are-surprisingly-potent-cause-global-warming

https://www.nature.com/articles/nclimate1068

Nevertheless, net radiative forcing due to contrail cirrus remains the largest single radiative-forcing component associated with aviation.

I will convolute this conversation further by stating that contrails (like all other clouds consisting of ice crystals) warm up the planet by letting shortwave radiation from the Sun through while being more reflective in longer infrared wavelenghts, thus trapping outgoing longwave radiation. Contrails themselves are also warming the planet up. It’s a small contribution in the grand scheme, but far from a trivial one.

The fourth one of those is unfortunately an almost plausible theory. Plenty of people are seriously advocating for studies into Stratospheric Aerosol Injection (SAI) in order to mitigate climate change so that the almighty free market would have more time to fix the problem without any need for systemic change.

But that wouldn’t be visible to the naked eye :D

Funnily enough, contrails like all other clouds composed of ice crystals actually warm the planet up by letting shortwave radiation from the sun through while reflecting longwave (infrared), effectively trapping heat. Thcker and lower clouds are more effective at reflecting shortwave radiation.