One question: Since contrails and water vapour stay far less time in the atmosphere than CO2, why should they have such large impact? Isn’t one of the most serious aspect of the climate system’s CO2 poisoning that CO2 stays in the atmosphere for thousands of years?
Most of the warming from CO2 emissions is not due to the emissions this year, but the cumulative effect (which persists) over the past 80 years. But for contrails, the warming impact is only really from those created very recently as you mentioned, see this graph:
Contrails contribute roughly 2% to the world’s effective radiative forcing; tackling them would reduce that by a similar amount
We would only need to have 5% planes slightly redirected to avoid producing the most harmful contrails, which tackles around 80% of contrail climate warming avoided, and it would only cost on average $1 of avoiding warming equivalent to one tonne of CO₂
Reducing contrails does not mean we don’t also need to tackle CO2 emissions from aviation. Ultimately that is the persistent driver of long-term temperature change. What tackling contrails now would do is slightly reduce the rate of warming. It is not an excuse or a substitute for finding a way to decarbonise jet fuel.
One question: Since contrails and water vapour stay far less time in the atmosphere than CO2, why should they have such large impact? Isn’t one of the most serious aspect of the climate system’s CO2 poisoning that CO2 stays in the atmosphere for thousands of years?
If you have the time, this is a great article on this subject: https://www.sustainabilitybynumbers.com/p/eliminating-contrails or this one https://notebook.contrails.org/comparing-contrails-and-co2/
Most of the warming from CO2 emissions is not due to the emissions this year, but the cumulative effect (which persists) over the past 80 years. But for contrails, the warming impact is only really from those created very recently as you mentioned, see this graph:
https://notebook.contrails.org/content/images/2025/08/2019_rf.svg
Contrails contribute roughly 2% to the world’s effective radiative forcing; tackling them would reduce that by a similar amount
We would only need to have 5% planes slightly redirected to avoid producing the most harmful contrails, which tackles around 80% of contrail climate warming avoided, and it would only cost on average $1 of avoiding warming equivalent to one tonne of CO₂
Reducing contrails does not mean we don’t also need to tackle CO2 emissions from aviation. Ultimately that is the persistent driver of long-term temperature change. What tackling contrails now would do is slightly reduce the rate of warming. It is not an excuse or a substitute for finding a way to decarbonise jet fuel.