CORRESPONDENCE
18 May 2021
Contrails: tweaking flight altitude could be a climate win
Ken Caldeira & Ian McKay
By our calculation, preventing most of the damaging impact of aircraft vapour trails (contrails) on climate would cost less than US$1 billion per year and the net value of the benefit could be more than 1,000 times that. We know of no comparable climate investment with a similarly high likelihood of success.
Contrails account for roughly 2% of global warming because they cause cirrus clouds to trap outgoing infrared radiation. The flights responsible are typically within 1,000 metres of trajectories that are much less damaging to the atmosphere, so planes routed to higher or lower altitudes would burn less than 0.1% more fuel (R. Teoh et al. Environ. Sci. Technol. 54, 2941–2950; 2020).
The warming effect of the extra emissions is likely to be more than offset by the reduction in vapour-trail formation (see B. Kärcher Nature Commun. 9, 1824; 2018). Furthermore, any drop in altitude would be insufficient to affect health costs from particulate matter and noise on the ground.
Addressing climate change could cost as much as US$100 trillion (D. P. van Vuuren et al. Nature Clim. Change 10, 329–334; 2020). Abating even 1% of this cheaply could therefore represent a trillion-dollar economic opportunity.
https://www.nature.com/articles/d41586-021-01339-7
