By David Bell at Brownstone dot org.

Geoengineering in the form of modifying the weather happens. It can save decimation of farmer livelihoods by mitigating droughts, and it can risk the global food supply by reducing crop growth. Like nuclear fission, it's useful in the hands of sane people working with the knowledge and assent of the wider community, or it has the potential to destroy much of what humankind has built if left in the hands of psychopaths.

If we can approach it in a calm and rational manner, we may yet stop the psychopaths.

During the Second World War, bomber crews were said to hate the contrails their planes produced, providing white fingers across the sky that pointed enemy fighters directly at them. These have seemingly exploded across our skies as commercial air travel has multiplied, but like boiling frogs, surprisingly few really noticed until others pointed out the heat.

Living in Geneva, Switzerland, during the weeklong grounding of aircraft due to the eruption of the Eyjafjallajökull volcano in Iceland in 2010, we had clear spring skies for the first time. Not a trail, not a wisp of residual cloud. Normal, it turned out, was not natural.

Condensation trails, or contrails, are clouds formed from condensation and from the water and particles that are emitted from aircraft engine exhaust. Fine particles released in the right conditions form a nidus on which droplets can form in humid, cold air. Jet engines also emit water as a combustion product. The very low pressure on the upper wing surface, the reason airplanes stay up in the air, also allows water vapor to precipitate.

This is well-documented, almost as old as high-flying aircraft, and annoying when you want to photograph a good sunset in much of Europe or North America.

Contrails can contribute to cirrus cloud formation, while aircraft changing altitude can also create some really otherworldly holes in cloud layers, such as on airport approaches. Clouds come and go naturally, from the ground to the upper atmosphere, if the conditions are right. Aircraft just help the process. And as clouds have sharp edges (when viewed from a distance), contrails can seem to turn on and off for the same reason (temperature and humidity at various altitudes).

There is a school of thought that streaks across the sky, or most of them, only began to appear recently and are the result of nefarious intent - geoengineering. The theory is that a whole hidden industry exists to make chemicals, transport them to airports, install them on commercial (i.e., passenger) aircraft or place them in fuel, and then release them at certain times or in certain regions.

This, performed at scale, would require thousands of willing people, who all remain silent on the issue. This is possible, but people talk, including pilots, fuelers, manufacturing workers, truck drivers, and airport security guards, so it is a little hard to imagine at scale. Part of an air force may follow some stupid government agenda, and perhaps do. But that is a tiny minority of flights.

However, airborne geoengineering does happen. It has for nearly a century, particularly with the intent to provide rain during droughts or more routinely in arid inhabited regions. In Australia and the United States, for instance, government agencies have for many decades sprayed compounds such as silver iodide from an aircraft to precipitate water vapour and cause rain during droughts. The hope is to save cattle farmers from ruin or augment a city's failing water supply.

These are not bad things, while mass cattle death and bankruptcy often are.

Geoengineering can also be unbelievably stupid. The British government is planning to fund high-altitude geoengineering to block sunlight. This is a pet project of some very rich people who consider themselves geniuses, and it is a real thing - I have directly heard their discussions on similar projects from people who can pay for them.

It is based on the interesting conviction that whil...