MMet Meteorology and Climate graduate and University of Reading PhD student Simon Lee is lead author of "Increased shear in the North Atlantic upper-level jet stream over the past four decades", a study published in international science journal Nature.
Co-authored with Professor Paul Williams and Dr Thomas Frame from the Department of Meteorology, the paper drew on work Simon carried out as part of his final-year dissertation for the integrated master's degree.
The study showed how the vertical west-to-east wind shear (the change in wind speed with height) has increased by around 15% as a result of climate change.
"Over the last four decades, temperatures have risen most rapidly over the Arctic, whilst in the stratosphere – around 12km above the surface – they have cooled. This has created a tug-of-war effect, where surface temperature changes act to slow the jet down, while temperature changes higher up act to speed it up.
Our study shows these opposing effects currently balance out, meaning the speed of the jet stream has not changed. However, we looked for the first time at the wind shear, where significant change has previously gone unnoticed.
This strengthens previous projections for increased clear-air turbulence, as we can see an increase in one of the driving forces has happened already. This has serious implications for airlines, as passengers and crew would face a bigger risk of injury.
Indications of a stronger jet stream in the future suggest the upper-level tug will eventually win out. This would also affect airlines by increasing flight times from Europe towards the US and speeding up flights the other way."