The research is frankly in early days, but I know and work with Paul Williams, and the article is a reasonable explanation of some aspects of his work.
The basic principle is quite simple - increased energy in the atmosphere (global warming / climate change / call it what you will) is particularly causing increased circulation in the atmosphere, and that is putting more energy into the jetstreams.
The north polar jetstream is particularly significant because of its importance in transatlantic flight. There's good evidence that the NPJ is becoming more energetic - this has two impacts: one is that the Rossby Waves (the meanders in the jetstream) are getting wider, another is that the core velocity in the NPJ is greater. This we know.
Because major CAT encounters are particularly associated with the edges of the jetstream, then theoretically this is going to both create more opportunities for CAT encounters (as there will be more intersections of the NPJ) and more severe CAT (because of the greater sheer stresses caused by the greater core velocities).
Anecdotally, this "seems to be" true, but at the moment, the hard evidence is pretty weak. We're working with one major carrier to mine their flight recorder data, and as we go further will probably be more players we talk to as well.
But it would not be true to say that we know a lot yet - we're at the start of a research journey here. Nonetheless, if we are right - it's important, and that's why we're working on it.
There are a load of other effects we're looking at as well - if anybody happened to be at Farnborough Airshow this year, on the Wednesday, you might have heard me give a talk on it.
G