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Discussion papers
https://doi.org/10.5194/cp-2018-164
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-2018-164
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 10 Dec 2018

Research article | 10 Dec 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Climate of the Past (CP).

Identifying teleconnections and multidecadal variability of East Asian surface temperature during the last millennium in CMIP5 simulations

Satyaban B. Ratna1, Timothy J. Osborn1, Manoj Joshi1, Bao Yang2, and Jianglin Wang2 Satyaban B. Ratna et al.
  • 1Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich, NR2 2BP, United Kingdom
  • 2Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, 730000, China

Abstract. We examine the relationships in models and reconstructions between the multidecadal variability of surface temperature in East Asia and two extratropical modes of variability: the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal oscillation (PDO). We analyze the spatial, temporal and spectral characteristics of the climate modes in Last Millennium, Historical and pre-industrial control simulations of three CMIP5/PMIP3 GCMs, to assess the relative influences of external forcing and unforced variability. These models produce PDO and AMO variability with realistic spatial patterns and their spectral characteristics. AMO internal variability strongly influences East Asia temperature in one model (bcc-csm1-1), but has a weak influence in the other two (CCSM4 and MPI-ESM-P). In all three models, external forcing greatly strengthens these statistical associations and hence the apparent teleconnection with the AMO. PDO internal variability strongly influences East Asian temperature in two of the three models, but external forcing makes this apparent teleconnection much weaker. This indicates that the AMO-East Asian temperature relationship is partly driven by external forcing whereas the PDO-temperature relationship is largely driven by internal variability. External forcing confounds attempts to diagnose the teleconnections of internal multidecadal variability. Using AMO and PDO indices that represent internal variability more closely and minimising the influence of external forcing on East Asia temperature can partly ameliorate this confounding effect. Nevertheless, these approaches still yield differences between the forced and control simulations and they cannot always be applied to paleoclimate reconstructions, so we recommend caution when interpreting internal variability teleconnections diagnosed from reconstructions that contain both forced and internal variations.

Satyaban B. Ratna et al.
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Satyaban B. Ratna et al.
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Short summary
We examine the relationships in models and reconstructions between multidecadal variability of East Asian temperature and two extratropical modes of variability. The relationship between East Asian temperature and Pacific multidecadal variability is largely driven by internal variability, whereas with Atlantic multidecadal variability it is more strongly influenced by the presence or absence of external forcing. We discuss the implications for diagnosing teleconnections from reconstructions.
We examine the relationships in models and reconstructions between multidecadal variability of...
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