Climate change impacts storm tracks

In a newly published article, Nansen Legacy researcher and co-leader of RF-1, Prof. Camille Li (Bjerknessenteret, UiB), and coworkers demonstrate how climate change will impact storm tracks globally at midlatitudes. The work is part of the HAPPI project, and the results of the study are based on over 3000 simulations of weak warming scenarios by five different climate models. One of the predictions from the study is that storm tracks over the North Atlantic will extend further eastwards towards Northern Europe with at somewhere between 1.5 C and 2.0 C of global temperature rise.

Picture1
Storm tracks over the North Atlantic will change with increasing global temperatures, here shown for 1.5 C (left) and 2 C (right temperature increase. The colour coding indicates the strength of the storm. Figure from Li et al. (2018)

STORM TRACKS ARE HIGHLY VARIABLE FEATURES OF THE ATMOSPHERIC CIRCULATION – THEY ARE NOISY, CHAOTIC BEASTS.

The research article does not address how increasing global temperatures will impact storm tracks in the Arctic. Prof. Camille Li says “The HAPPI simulations suggest fewer storms over the high Arctic for the 1.5 and 2 degrees Ceclsius experiments. Other analyses looking at stronger warming scenarios agree, but find that individual storms could become more intense in certain places. With more moisture in the atmosphere and more open water, there are good reasons to expect more intense storms in some parts of the Arctic”. Li stresses that storm intensities and tracks most likely will not change uniformely across the Arctic, but differ greatly from location to location.

This is exactly what Li and others will investigate within The Nansen Legacy. Here, they intend to use a range of tools, from state-of-the-art climate models (like NorESM) to idealized models, which allow them to test physical mechanisms of how the the climate system works. A complicating factor for the study of storms in the Arctic compared to midlatitudes is that Li and coworkers will have to consider additional factors, such as sea ice and different boundary layer physics. As for the study of storm tracks at midlatitudes, Li and coworkers plan to use a whole suite of different climate models and large numbers of simulations for their work within The Nansen Legacy. Using a large ensemble of simulations is the only way “to overcome the large variability inherent in storm tracks”, says Li.

THE NEW OBSERVATIONAL CONSTRAINTS AND THE ARCTIC EXPERTISE IN THE NANSEN LEGACY PROJECT WILL BE EXTREMELY USEFUL FOR CONSTRAINING THE BEHAVIOUR OF STORM TRACKS AS THEY TRANSITION FROM MIDLATITUDES TO THE HIGH LATITUDES.