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Disentangling Global Warming, Multidecadal Variability, and El Niño in Pacific Temperatures

Wills, Robert C. and Schneider, Tapio and Wallace, John M. and Battisti, David S. and Hartmann, Dennis L. (2018) Disentangling Global Warming, Multidecadal Variability, and El Niño in Pacific Temperatures. Geophysical Research Letters, 45 (5). pp. 2487-2496. ISSN 0094-8276. doi:10.1002/2017GL076327.

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A key challenge in climate science is to separate observed temperature changes into components due to internal variability and responses to external forcing. Extended integrations of forced and unforced climate models are often used for this purpose. Here we demonstrate a novel method to separate modes of internal variability from global warming based on differences in time scale and spatial pattern, without relying on climate models. We identify uncorrelated components of Pacific sea surface temperature variability due to global warming, the Pacific Decadal Oscillation (PDO), and the El Niño–Southern Oscillation (ENSO). Our results give statistical representations of PDO and ENSO that are consistent with their being separate processes, operating on different time scales, but are otherwise consistent with canonical definitions. We isolate the multidecadal variability of the PDO and find that it is confined to midlatitudes; tropical sea surface temperatures and their teleconnections mix in higher‐frequency variability. This implies that midlatitude PDO anomalies are more persistent than previously thought.

Item Type:Article
Related URLs:
URLURL TypeDescription
Wills, Robert C.0000-0002-7776-2076
Schneider, Tapio0000-0001-5687-2287
Battisti, David S.0000-0003-4871-1293
Hartmann, Dennis L.0000-0002-4495-7774
Additional Information:© 2018 American Geophysical Union. Received 6 NOV 2017; Accepted 17 JAN 2018; Accepted article online 25 JAN 2018; Published online 15 MAR 2018. We thank T. Kohyama, K. Armour, T. Bischoff, M. Stuecker, and K.‐K. Tung for valuable conversations and feedback on this work. R. C. W. and D. L. H. acknowledge support from the National Science Foundation (grant AGS‐1549579). R. C. W. and D. S. B. acknowledge support from the Tamaki Foundation. The data sets used are documented in Smith et al. (2008) and Compo et al. (2011).
Funding AgencyGrant Number
Tamaki FoundationUNSPECIFIED
Subject Keywords:Pacific Decadal Oscillation; global warming; El Niño; internal variability
Issue or Number:5
Record Number:CaltechAUTHORS:20180411-105304038
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Official Citation:Wills, R. C., Schneider, T., Wallace, J. M., Battisti, D. S., & Hartmann, D. L. (2018). Disentangling global warming, multidecadal variability, and El Niño in Pacific temperatures. Geophysical Research Letters, 45, 2487–2496.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85744
Deposited By: Tony Diaz
Deposited On:11 Apr 2018 18:19
Last Modified:15 Nov 2021 20:31

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