Suppression of cold air outbreaks over the interior of North America in a warmer climate

In spite of the mean warming trend over the last few decades and its amplification in the Arctic, some studies have found no robust decline or even a slight increase in wintertime cold air outbreaks over North America. But fossil evidence from warmer paleoclimate periods indicates that the interior of North America never dropped below freezing even in the depths of winter, which implies that the maintenance of cold air outbreaks is unlikely to continue indefinitely with future warming. This study uses an air parcel trajectory analysis of cold air outbreaks in a pre-industrial vs a much warmer, Eocene-like climate to identify the mechanism of the suppression of cold extremes. We demonstrate a remarkable similarity in both the dynamics and diabatic effects acting on cold air masses in the two climate scenarios.

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