Here is a really interesting update – thanks to the BBC – on a question which has worried climate science for a long time – does the exhaust gas of high-flying aircraft make global warming worse? It is not only water vapour that is produced by the burned fuel (water vapour is a global warming gas) but the particulates inevitably ejected by these kerosene-burning engines function as nucleation points for the water which is “lying in wait” in the stratosphere to settle on these particles, thus creating high-level clouds which tend to trap extra heat. So what has this to do with hydrogen? After all, if the plane is fuelled by hydrogen, all the exhaust gas will be water vapour. Answer?
1. There will be no particulates emitted for the stratosphere’s own water vapour to settle on, therefore no heat-retaining clouds can be formed.
2. The researchers mentioned in the original article in “Environmental Research Letters” maintain that only a small shift in aircraft routing would be enough to preclude most of this water vapour drawback..
An interesting addendum from Sweden! If our concern is the contrail rather than just the fuel (hydrogen, which we advocate, rather than kerosene) then these ideas about jet engine redesign should interest our readers. Perhaps a hydrogen-fuelled engine featuring these design changes would really make a difference.
These features? (1) Open propellers, just like older aircraft, but driven by the jet, and allowing the plane to travel pretty fast. (2) Gearing the innards, so that the fan driving air into the engine goes at the optimal speed (slower than present engines) whilst the turbine itself revolves as fast as necessary.