CMIP6 models overestimate the North Atlantic eddy-driven jet persistence

Persistent fluctuations in the latitudinal position of the North Atlantic jet stream are associated with extreme weather anomalies, particularly over Europe. Therefore, it is crucial to understand how the jet stream persistence might change in response to increased greenhouse gases to deliver useful regional climate projections. This study examines the persistence of the North Atlantic jet stream latitudinal fluctuations in CMIP6 and ERA5. We found that CMIP6 models consistently overestimate the persistence compared to ERA5 during the historical period. This discrepancy appears linked to too weak transient eddies over the NATL in CMIP6 models.

By the end of the XXI century, CMIP6 models forced with the SSP585 scenario project a reduction of the jet fluctuations persistence of about 10% during the summer season. The evidence suggests this reduction is linked to a slower NATL jet during the summer months.