Do CMIP5 models reproduce observed low-frequency North Atlantic jet variability?

The magnitude of observed multi‐decadal variations in the North Atlantic Oscillation (NAO) is at the upper end of the range simulated by climate models and a clear explanation for this remains elusive. Recent research shows that observed multi‐decadal NAO variability is more strongly associated with North Atlantic (NA) jet strength than latitude, thus motivating a comprehensive comparison of NA jet and NAO variability across the CMIP5 models. Our results show that the observed peak in multi‐decadal jet strength variability is even more unusual than NAO variability when compared to the model‐simulated range across 133 historical CMIP5 simulations. Some CMIP5 models appear capable of reproducing the observed low‐frequency peak in jet strength, but there are too few simulations of each model to clearly identify which. It is also found that an observed strong multi‐decadal correlation between jet strength and NAO since the mid‐19th century may be specific to this period.

Details