Aviation Solutions
54%
Aviation contributes more to global warming than heating due just to CO2 emissions; contrails and other short-lived climate forcers (SLCFs) triple the heating effect [1]. Google, using artificial intelligence (AI), has predicted routes over the US that avoid the conditions that create contrails. After 70 test flights, it was found that these predictions reduced contrails by 54% compared with flights that didn't use the predictions [2].
  • Flights avoiding contrails used 2% more fuel but, since not all flight create contrails, this amounted to about 0.3% over a typical airline fleet. Contrail avoidance costs would be in the range of $5-25/ton of CO2, a cost-effective solution.
  • On average, only 15% of flights in the contiguous United States generate contrails. Contrails are concentrated in south-east and mid-west, and on the Pacific coast, and are twice as likely between the months of June and September. Ice-supersaturated (ISS) regions where contrails form tend to be wide but only a few hundred metres/yards tall.
    iss
    ISSR, at
    22,500m 36,000'
    , 9:00 am on November 15th 2014 [3].
    Flying around ISS areas is not cost effective but flying over them has benefits.

References:

[1] 'Using Google AI to help airlines prevent contrails' (Accessed on 16th November, 2023) https://sites.research.google/contrails/
[2] Page within this site: (Accessed on 16th November, 2023) https://numbers-matter.org/climate/problems/warming/causes#5 . . .
[3] 'Reducing global warming by airline contrail avoidance: A case study of annual benefits for the contiguous United States' (Accessed on 16th November, 2023) https://www.sciencedirect.com/science/article/pii/S259019821 . . .
92%
Aviation is responsibe for about 6% of the globe's warming. Contrails cause a large part of that heating. Flying above ice supersaturated regions where contrails form, rather than through them, can reduce the warming effects by as much as 92% for the United States. [1].
  • A daily decrease of 63% of net radiative forcing (NRF) is predicted for increases in elevation of
    600m 2000'
    and a decrease of 92% for an increase in elevation of
    1200m 4000'
    . In addition to route optimization for winds, routes should be also optimized for contrail avoidance.
  • The increase in fuel burnt due to the elevation gain is not significant due to lower drag at higher altitudes.
  • A different study [2] from Imperial College, London, examined Japan's airspace and determined that just 2% of flights were responsible for 80% of climate forcing in the airspace and that an increase or decrease in altitude of around 1.7% could reduce the contrail climate forcing by 59%.

References:

[1] 'Reducing global warming by airline contrail avoidance: A case study of annual benefits for the contiguous United States' (Accessed on 17th November, 2023) https://www.sciencedirect.com/science/article/pii/S259019821 . . .
[2] 'Small altitude changes could cut contrail impact of flights by up to 59 per cent' (Accessed on 17th November, 2023) https://www.imperial.ac.uk/news/195294/small-altitude-change . . .