<p>Previous studies using an emergent constraint have suggested that climate models underestimate the winter jet stream response to sea ice loss, casting doubt on the quality of mid-latitude climate projections. However, the robustness of this emergent constraint has been questioned. Here, we propose a more robust emergent constraint based on lower stratospheric winds. Using coordinated sea ice loss experiments with bespoke versions of two state-of-the-art climate models along with a multi-model archive, we identify a strong relationship between these winds and the jet stream response. The new emergent constraint reduces the uncertainty in the response by 62% and indicates that the real-world response closely matches the multi-model mean—suggesting no systematic underestimation, in contrast to earlier studies. Our results underscore the importance of reducing lower stratospheric wind biases and increase confidence in climate model projections of a future poleward shift of the jet stream in response to global warming.</p>