If it can trap it coming up from below, then by definition it's also going to reflect back whatever's coming down from above too - so the net effect is nothing.

And then there are the conspiracy theorists who say there are no such things as contrail cirrus clouds. They'll insist that those are actually "chemtrails."

Ummm... clouds (even cirrus clouds) REFLECT the sun during the day, cooling the earth. At night clouds have no sun to reflect so they end up blocking infrared radiation from escaping to space, trapping heat. Clouds in the daytime cool. Clouds at night warm.

Seems to me, those contrails (clouds) are stopping the suns rays up there, thus shading the lower atmosphere and earth. Who is to say, those contrails are not mitigating global warming to some extent? Why not use that wasted money on heat reflecting materials on roof tops and highways, thus reflecting all that heat back up instead of being absorbed?

This, along with the eagle slicing drone knock-down idea is the dumbest thing I've seen on New Atlas. Who wants 'planes to use nearly 10% more fuel? Who ever felt warmer when the sun was obscured by clouds? Who has ever seen a sky obscured by contrails? Also, the moisture is in the exhaust , it is a product of combustion.

This really only applies to night flights or at least contrails that last into the dark period for the area.
Otherwise "global dimming" which gives a cooling effect is the dominate one as witnessed in the change in temperatures after the 911 attack when aircraft in the US were grounded. This grounding caused a 1 degree change in the difference between night and day temperatures.

Perhaps only night flights could be re-directed to minimise the negative effects of the contrails?l

There is also another factor - if the temperature is made warmer at night - might this reduce heating requirements (and consequently CO2 generation) over built up areas?

Back in the days of 9-11 when they stopped all aircraft from flying, there was a scientist that had predicted that if that were to happen it would cause a warming trend. The idea was the contrails blocked the sun and caused cooling. He measured the temperatures (with the absence of aircraft) around the USA and found that to be true.

You can take the temperature of the night sky (or day sky) with an IR viewer and tell right away the effect of these clouds. The water layer may have a larger effect than the ice.

Y'know what would really fix the problem? 11,173,456 quintillion 60mm black plastic balls. Just spread 'em out over the ocean and reduce all that water vapor. Then when Global Cooling sets back in, just collect them and start burning down all the forests again. SIMPLE!

(Jackie Hodges) I remember 9/11 and that study. Years ago I even tried to promote the reformulation of jet fuels to provide more opaque contrails for daytime airline routes and a different fuel formulation that minimized contrails at night. Even better would have been additives which could accomplish the same thing with any fuel. I have even suggested that changing the standard airline altitudes could accomplish the same thing depending on the weather. I even got an email from Richard Branson that he wasn't interested. Of course this didn't fit in with the global warming hysteria that wants to demonize all air travel as bad rather than a possible solution.