Firstly, there's no such thing as "the transatlantic flight path."

North Atlantic tracks (see here) change daily, the general idea being to avoid headwinds when westbound and pick-up tailwinds when eastbound, while simultaneously achieving safe traffic separation.

So flights avoid the jet stream when westbound and try to get in it when eastbound. Everything possible is done to achieve a minimum fuel burn.

The jet stream is not turbulent in itself. An eastbound aircraft flying right in the centre of the jet stream will enjoy smooth air and a tailwind of up to 200 knots. However, at the edges of the jet stream there is turbulence where the fast moving core meets the slower moving surrounding air. The faster the jet stream, the greater the turbulence. Flying in this turbulence can be uncomfortable, but is never dangerous – airframes are easily able to withstand the relatively low forces involved. (The only turbulence which poses a danger to civil aircraft is that associated with thunderstorms – cumulonimbus clouds.)

The jet stream is driven by the temperature gradient between cold Arctic air and warm temperate air. The higher the gradient, the stronger the jet stream. It is claimed the Arctic is warming at a higher rate than the rest of the planet, so that should lead to a lower temperature gradient and hence a weaker jet stream, with lower turbulence at its edges.

Williams and Joshi write; "At typical cruise altitudes in the northern half of the North Atlantic flight corridor in winter, most diagnostics show a 10–40 per cent increase in the median strength of turbulence and a 40–170 per cent increase in the frequency of occurrence of moderate-or-greater turbulence."

In my experience (over 30 years as an airline pilot), light turbulence associated with a jet stream is common, moderate turbulence rare, severe turbulence unheard of.

When deciding to investigate turbulence and whether we have seen any changes over the last few decades, do you think the scientists phoned up Boeing to see if they had any useful data (You'd think they might be interested in knowing turbulence was increasing significantly) or interview veteran pilots such as Scottie above? If we haven't noticed any effect up to now you might then question future model predictions for notable changes in a similar time period.

"4. it's a big deal if planes like the Air France one in Brazil crashed cos of Climate Change"

IIRC this was nothing to do with turbulence - it was pilot error (a high speed, high altitude stall) as a consequence of a frozen air data sensor (Scottie, please confirm?).

Apart from that, Scottie says it all.

More pure climate pr0n from the people that brought you such gems as 'our children won't know what snow is'. I'm impressed by the bare-faced cheek (chutzpah) being exhibited by the alarmist clan about all the things that can happen, or rather *will happen* if you set up a model to provide 'evidence'