Abstract The response of transient atmospheric waves to anthropogenic emissions holds large weather and climate impacts in the mid‐latitudes. Notably, in the Southern Hemisphere, future changes in atmospheric waves differ fundamentally between the winter and summer seasons. By the end of this century, austral mid‐latitude waves are projected to intensify in winter but to shift poleward in summer. Here we find that an asymmetric response of the waves across scales drives their seasonally asymmetric changes. Specifically, a strengthening of large‐scale waves contributes to the future intensification in winter, while a reduced intensity of small‐scale waves leads to the poleward shift of the waves during summer. Our analysis further reveals that seasonal differences in upper‐level warming patterns are responsible for the contrasting future changes in the waves across scales and seasons. These results underscore the need for detailed scale‐sensitive analyses to unravel the intricate effects of anthropogenic forcings on the mid‐latitude climate.

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