Understanding the Southern Hemisphere's Weather Mover

The Southern Hemisphere's summertime eddy-driven jet (EDJ) plays a big role in shaping weather patterns. It acts like a bridge between local climates and larger global weather systems. However, predicting how this jet will change in the future is tricky. Global climate models (GCMs) struggle with this because they can't perfectly predict things like tropical warming, changes in the stratospheric polar vortex, or uneven heating in the Pacific Ocean. Researchers have come up with a new way to understand and predict these changes. They used a mix of observations, reanalysis data, and future climate scenarios from the Coupled Model Intercomparison Project (CMIP). Their findings show that tropical warming has been on the lower end of what these models predicted. At the same time, the stratospheric polar vortex has been getting stronger, which also affects the EDJ. About half of the changes in the EDJ's position can be directly linked to global warming. The other half is influenced by these remote drivers, but it's not clear how much of that is also due to global warming. Interestingly, the climate models seem to get the direction of the EDJ's shift right, but they underestimate how much stronger it's getting. The new approach combines cause-and-effect reasoning with climate storylines. This helps narrow the gap between understanding past changes and predicting future ones. This new method gives a solid, physics-based way to figure out possible future climate scenarios. It's a step forward in making sense of how our climate is changing and what we might expect in the years to come.