@katnyps
PlanDeRaccordement
Yeah condensation trail = contrail = water - they mimic the effect of certain types of clouds and trap heat in the atmosphere and I think contribute to around a third of the greenhouse effect of aircraft engines (and would still be an issue with hydrogen engines)
Ah, but today’s airplane contrail is not just water vapour, that’s why it’s also called a chemtrail. For a contrail to form, at the 33,000ft most airplanes cruise at, it needs exhaust particles to trigger condensation. Exhaust particles include unburned fuel, VOCs, hydrocarbons, alcohol, ozone, soot, even engine wear particles. A NASA study showed that contrail formation was reduced by 50-70% due to fewer soot particles when using a 50% biofuel/50% jet fuel mix.
Yes, water vapor by itself is another greenhouse gas produced by the combustion of fuel, and although the radiative forcing (difference between the energy absorbed through the Earth’s atmosphere compared to the energy that is reflected back into space) is lower than that of CO2, it still contributes towards global warming.
Hydrogen combustion would produce about 2.6 times more water vapor than kerosene fuel. In a study about the climate change effects of hydrogen aircraft, Ponater et al. [7] evaluated the individual and accumulated effects of the emissions of a hydrogen-based flight to a kerosene-based flight. The study concluded that the positive effects of a zero-CO2 combustion, would offset the drawback of increased water vapor exhaust. Moreover, CO2 has a lifetime in the atmosphere of up to
100 years, while that of water vapor can go from a few days up to 1 year [4]. Regarding condensation trails, due to the absence in solid particles at the exhaust of the engine when burning hydrogen, ice crystals have no-where to nucleate, so the number of water crystals formed at the exhaust would decrease. Nevertheless, due to the increased amount of water vapor exhaust, the crystals that do nucleate, would have a larger size. The overall effect is expected to decrease the radiative forcing effect of contrails. The end result, according to the study would mean that the radiative forcing from aviation could be 20-30% lower by 2050 and 50-60% by 2100 if LH2 aircraft were introduced [7].
www.iata.org/contentassets/d13875e9ed784f75bac90f000760e998/fact_sheet7-hydrogen-fact-sheet_072020.pdf