NAO predictability from external forcing in the late 20th century

Abstract The North Atlantic Oscillation (NAO) is predictable in climate models at near-decadal timescales. Predictive skill derives from ocean initialization, which can capture variability internal to the climate system, and from external radiative forcing. Herein, we show that predictive skill for...

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Bibliographic Details
Published in:npj Climate and Atmospheric Science
Main Authors: Klavans, Jeremy M., Cane, Mark A., Clement, Amy C., Murphy, Lisa N.
Other Authors: NSF | GEO | Division of Atmospheric and Geospace Sciences, NSF | Directorate for Geosciences
Format: Article in Journal/Newspaper
Language:English
Published: Springer Science and Business Media LLC 2021
Subjects:
Atmospheric Science
Environmental Chemistry
Global and Planetary Change
North Atlantic
North Atlantic oscillation
Online Access:http://dx.doi.org/10.1038/s41612-021-00177-8
http://www.nature.com/articles/s41612-021-00177-8.pdf
http://www.nature.com/articles/s41612-021-00177-8
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Summary:Abstract The North Atlantic Oscillation (NAO) is predictable in climate models at near-decadal timescales. Predictive skill derives from ocean initialization, which can capture variability internal to the climate system, and from external radiative forcing. Herein, we show that predictive skill for the NAO in a very large uninitialized multi-model ensemble is commensurate with previously reported skill from a state-of-the-art initialized prediction system. The uninitialized ensemble and initialized prediction system produce similar levels of skill for northern European precipitation and North Atlantic SSTs. Identifying these predictable components becomes possible in a very large ensemble, confirming the erroneously low signal-to-noise ratio previously identified in both initialized and uninitialized climate models. Though the results here imply that external radiative forcing is a major source of predictive skill for the NAO, they also indicate that ocean initialization may be important for particular NAO events (the mid-1990s strong positive NAO), and, as previously suggested, in certain ocean regions such as the subpolar North Atlantic ocean. Overall, we suggest that improving climate models’ response to external radiative forcing may help resolve the known signal-to-noise error in climate models.

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