That article was way more interesting than I expected.

Unfortunately, contrails tend to have a warming effect. While they increase the amount of sunlight reflected away from Earth, they ultimate trap more heat in the atmosphere than they bounce away.

It might sound like a minor thing, but the science suggests their warming impact is likely larger than that of fossil fuel emissions from global aviation operations. One study performed in 2018 suggested that contrails are doing more to heat up the Earth than all the CO2 emitted by aviation since 1940.

That was particularly surprising.