My work as a climate scientist in Oxford’s Dept of Physics revolves around the jet stream; a great current of fast-moving air that encircles the globe. It is often confused with the Gulf Stream, which is a warm ocean current off the coast of Florida. In contrast, the jet stream is basically a wind system.
Here in Oxford, we have worked on many different aspects of the jet stream, such as how it varies over weeks, years and decades, and how we can better predict these changes in advance. More broadly, Oxford scientists have studied jets in the oceans, in tanks of water in the lab, and even jets in the atmospheres of other planets.
Our interest in the jet stream is based on its profound impact on our weather patterns. The jet stream is arguably the greatest weather system on Earth. If you were only given one piece of information from which to infer something about the weather, then across much of the Earth’s surface you’d want it to be about the jet stream.
Awareness of the importance of the jet stream has risen to the point where it is routinely mentioned in daily weather forecasts, and often blamed in news reports for the latest bout of severe weather. The increasing interest in the jet inspired me to look deeper into its history and its impact, and as a result I recently wrote a popular science book: Jet Stream: A Journey through our Changing Climate, and learnt several fascinating stories along the way.
For example, I learnt about an early contender for the discovery of the jet stream: James Glaisher, hero of this year’s film ‘The Aeronauts’. In several daredevil balloon ascents over England, Glaisher noted a strong, warm wind from the southwest, and correctly speculated that this could be a factor in Europe’s relatively mild winters.
Fifty years later, the jet stream was rediscovered by dedicated Japanese weather observer Wasaburo Ooishi. Intent on spreading news of his discovery to the widest possible audience, Ooishi decided to write his paper in the new, global language of Esperanto, and sadly it sank without trace. This served the Japanese well during WWII, when they tried to attack the US mainland by sending fleets of balloon bombs riding along the jet.
By the end of WWII, however, the jet stream had become widely known, thanks to several unfortunate incidents in which high-altitude warplanes were sent wildly off course. Rapid progress was made in the decades that followed, and today the jet is well observed, carefully monitored and solidly tied to the fundamental laws of physics.
Our understanding and our simulation capabilities have improved to the point where we are even able to issue forecasts for how the jet will behave, on average, a whole season ahead. Albeit not perfect, these predictions are right more often than they are wrong, seemingly able to defy the laws of chaos theory which so constrain weather forecasts.
But new challenges are now emerging. The world has warmed by one degree Celsius since Glaisher took his pioneering observations, and theories abound for how this warming will affect the jet stream. Many recent extreme weather events have involved a highly disturbed jet, and it’s possible this is a side-effect of climate change, but we still have much to learn about the jet stream before we can be sure of this.
