Disentangling Global Warming, Multidecadal Variability, and El Niño in Pacific Temperatures. Issue 5 (15th March 2018)

• Record Type: Journal Article
• Authors: Wills, Robert C.; Schneider, Tapio; Wallace, John M.; Battisti, David S.; Hartmann, Dennis L.
• Is Part Of: Geophysical research letters. Volume 45:Issue 5(2018)
• Page Start: 2487
• Page End: 2496
• Publication Date: 2018-03-15
• Subjects: Pacific Decadal Oscillation -- global warming -- El Niño -- internal variability; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL076327
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: 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. Key Points: A novel method is presented to separate internal variability from global warming based on differences in time scale and spatial pattern The key features of the Pacific Decadal Oscillation and El Niño‐Southern Oscillation are consistent with their being separate processes Decadal variability associated with the Pacific Decadal Oscillation is confined to the midlatitude North Pacific