May 23, 2025, ©. Leeham News: We do a Corner series about the state of developments to improve the emission situation for Air Transport. We try to understand why development has been slow.
We have since we started in October last year looked at:
We examined Alternative 1’s emissions improvement two weeks ago and compared it to the normal improvement in new airliners’ fuel consumption last week. Now, we examine the improvement that SAF can offer compared to the other two.
May 16, 2025, ©. Leeham News: We do a Corner series about the state of developments to improve the emission situation for Air Transport. We try to understand why development has been slow.
We have since we started in October last year looked at:
We examined Alternative 1’s emissions improvement last week and now compare it to the normal improvement in fuel consumption, and thus emissions, that the airline industry is continuously working on.
May 9, 2025, ©. Leeham News: We do a Corner series about the state of developments to improve the emission situation for Air Transport. We try to understand why development has been slow.
Since we started in October last year, we have looked at:
Last week, we listed some base data about the present situation for Global Air Transport. We will now use this data to calculate the effect of air transport on global warming from the three alternatives.
May 2, 2025, ©. Leeham News: We do a Corner series about the state of developments to improve the emission situation for Air Transport. We try to understand why development has been slow.
We have since we started in October last year looked at:
Before we proceed, we shall examine some facts about the scale of the emission/global warming influences from Air Transport.
April 25, 2025, ©. Leeham News: We do a Corner series about the state of developments to improve the emission situation for Air Transport. We try to understand why development has been slow.
Over the last Corners, we examined the non-CO2 effects of Air Transport that contribute to global warming. Contrails had the largest effects, even larger than the CO2 emissions from Air Transport.
To complete the review of our progress with lower emission actions for Air Transport, we will examine the present situation with SAF, Sustainable Aviation Fuel.
April 18, 2025, ©. Leeham News: We do a Corner series about the state of developments to improve the emission situation for Air Transport. We try to understand why development has been slow.
We examine the non-CO2 effects of Air Transport that contribute to global warming. Over the last weeks, we have looked at contrails, which have the largest impact on global warming, larger than CO2, Figure 1.
NOx is a smaller contributor, but it contributes about 20% of the total to Global Warming.
April 11, 2025, ©. Leeham News: We do a Corner series about the state of developments to improve the emission situation for Air Transport. We try to understand why development has been slow.
We now examine the non-CO2 effects of Air Transport that contribute to global warming. Of these, contrails have the largest impact, Figure 1.
In the last Corner, we described encouraging results from airline flight trials with warming contrail avoidance. What is required to move from trials to warming contrail avoidance for regular flights?
April 4, 2025, ©. Leeham News: We do a Corner series about the state of developments to improve the emission situation for Air Transport. We try to understand why development has been slow.
We now examine the non-CO2 effects of Air Transport that contribute to global warming. Of these, contrails have the largest impact.
Contrails form when aircraft gas turbine engines emit soot particles into water vapor-saturated areas with low temperatures, where the soot particles act as condensation nuclei and the droplets freeze into ice crystals.
The report from Lee et al. (2021) lists non-CO2 effects as more important for Global Warming from Air Transport than CO2 emissions from burning hydrocarbon fuels, Figure 1.
March 21, 2025, ©. Leeham News: We do a Corner series about the state of developments to improve the emission situation for Air Transport. We try to understand why development has been slow.
After covering alternative propulsion concepts to lower CO2 and NOx emissions, we now study air transport’s non-CO2 effects on global warming. Of these, contrails have the largest impact.
Contrails form when aircraft gas turbine engines emit soot particles into low-temperature water vapor-saturated areas in the atmosphere. The soot particles form condensation nuclei, and the developed droplets freeze to ice crystals that form contrails.
Figure 1. The net Radiative Forcing of flights during 2019. Source: The report “Global aviation contrail climate effects from 2019 to 2021” from 2024.
March 21, 2025, ©. Leeham News: We do a Corner series about the state of developments to replace or improve hydrocarbon propulsion concepts for Air Transport. We try to understand why development has been slow.
Last week, we examined MTU’s WET engine concept, which utilizes a water capture process in a Turbofan to lower emissions, such as NOx, and reduce the water content in the exhaust, thereby reducing contrail risk. The week before, we looked at a similar concept, focused on a hydrogen burn process from Pratt & Whitney called HySIITE.
Both concepts capture water in the turbofan’s exhaust and can then release it in a way that avoids contrail generation. Contrails have garnered significant attention in recent years, as research has raised the possibility that persistent contrails can contribute as much or more to global warming than the CO2 released during the Turbofan combustion process in an airliner.
We will spend the next Corners digging deeper into the question of air transport’s non-CO2 effects that contribute to global warming. Contrails have the largest impact on these non-CO2 contributions.