American Airlines and Google were able to cut contrails made by jets by more than half during a small trial, a move that could significantly reduce the global-warming footprint of the travel industry, but with a slight increase to fuel use.
Same here, and I’m a bit confused since it was recently discovered that clouds formed due to ship sulfur pollution were helpful to reduce warming, and reducing the sulfur pollution actually caused heating.
Why do those clouds cool the planet while contrails heat it? Is it just the difference in altitude, having the clouds higher up for some reason acting more insulating?
It’s exactly as you said—different clouds have different effects on the climate. Some warm things, some cool things.
It’s more complicated than this, but the way I learned in school was that all clouds reflect sunlight, but they can also block some IR from leaving the earth. Low clouds absorb IR from the surface but re-emit it at a similar level to the ground because they are a similar temperature. In this case the reflective effect dominates, so most low clouds have a cooling effect. But high clouds are very cold—this means they absorb the same IR from the surface but emit far less into space, keeping the planet warmer. This dominates the reflective influence, so high clouds can warm the climate.
Clouds at night are particularly warming, since they don’t reflect sunlight. For this reason, redeye flights have a greater warming effect than other flights. Supersonic jets and other very high flying aircraft can also be extra harmful.
TIL contrails are a legitimate concern and have environmental impact!
Same here, and I’m a bit confused since it was recently discovered that clouds formed due to ship sulfur pollution were helpful to reduce warming, and reducing the sulfur pollution actually caused heating.
https://www.science.org/content/article/changing-clouds-unforeseen-test-geoengineering-fueling-record-ocean-warmth
Why do those clouds cool the planet while contrails heat it? Is it just the difference in altitude, having the clouds higher up for some reason acting more insulating?
It’s exactly as you said—different clouds have different effects on the climate. Some warm things, some cool things.
It’s more complicated than this, but the way I learned in school was that all clouds reflect sunlight, but they can also block some IR from leaving the earth. Low clouds absorb IR from the surface but re-emit it at a similar level to the ground because they are a similar temperature. In this case the reflective effect dominates, so most low clouds have a cooling effect. But high clouds are very cold—this means they absorb the same IR from the surface but emit far less into space, keeping the planet warmer. This dominates the reflective influence, so high clouds can warm the climate.
Clouds at night are particularly warming, since they don’t reflect sunlight. For this reason, redeye flights have a greater warming effect than other flights. Supersonic jets and other very high flying aircraft can also be extra harmful.