Think stuff like big jets, or container ships. If you sit down and crunch the numbers for any non-carbon energy carrier, you either end up sinking the ship or with a fuel tank twice the size of the cargo.
But I agree container ships would be a good application of this. Container ships also have pretty high efficiency internal combustion engines (about 50%), meaning there's less advantage in electrification there than for land vehicles which often have 15-25% efficient engines. And it allows low particulates, which is one of the main forcing regulations on shipping powertrains nowadays, without the overhead of cryogenic LNG.
However, container ships use ridiculously cheap bunker fuel instead of highly refined gasoline.
The effect (not counting contrails) is about double the effect of CO2 emissions alone. Including contrails, it may be even higher. There are mitigation strategies to deal with these non-CO2 radiative forcing effects, though it's very complicated.
Good article: https://www.carbonbrief.org/explainer-challenge-tackling-avi...
https://elib.dlr.de/68051/1/fugl-2010-4648.pdf
which says
> At pressures greater than 500 hPa (i.e. below roughly 6 km), the forcing [of water vapor] is assumed to be negligible
So flying below 6km would help a lot for impact of water vapor. However, given this was not yet acted upon, IPCC is probably right that
> the effect of water vapour emissions is likely to be a significant, or even the dominant, contributor to their climate forcing.
This is even worse given the projections of aviation expansion. Right now the water does not seem to be a big problem and it could stay that way - water lifetimes even in stratosphere is counted in years, as opposed to centuries for CO2 - but if aviation expands, then it becomes more serious than CO2.