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Uncertainty in the ENSO amplitude change from the past to the future
Author(s) -
Watanabe Masahiro,
Kug JongSeong,
Jin FeiFei,
Collins Mat,
Ohba Masamichi,
Wittenberg Andrew T.
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2012gl053305
Subject(s) - amplitude , precipitation , climatology , el niño southern oscillation , coupled model intercomparison project , climate model , nonlinear system , ensemble average , oscillation (cell signaling) , phase (matter) , environmental science , multivariate enso index , climate change , la niña , meteorology , physics , geology , chemistry , oceanography , quantum mechanics , biochemistry
Due to errors in complex coupled feedbacks that compensate differently in different global climate models, as well as nonlinear nature of El Niño‐Southern Oscillation (ENSO), there remain difficulties in detecting and evaluating the reason for the past and future changes in the ENSO amplitude, σ niño . Here we use physics parameter ensembles, in which error compensation was eliminated by perturbing model parameters, to explore relationships between mean climate and variability. With four such ensembles we find a strong relationship between σ niño and the mean precipitation over the eastern equatorial Pacific ( P ¯ ni n ˜ o ). This involves a two‐way interaction, in which the wetter mean state with greater P ¯ ni n ˜ o acts to increase the ENSO amplitude by strengthening positive coupled feedbacks. Such a relationship is also identified in 11 single‐model historical climate simulations in the Coupled Model Intercomparison Project phase 5 despite mean precipitation biases apparently masking the relationship in the multi‐model ensemble (MME). Taking changes in σ niño andP ¯ ni n ˜ o between pre‐industrial and recent periods eliminates the bias, and therefore results in a robust σ niño – P ¯ ni n ˜ o connection in MME, which suggests a 10–15% increase in the ENSO amplitude since pre‐industrial era mainly due to changing mean state. However, the σ niño – P ¯ ni n ˜ oconnection is less clear for their future changes, which are still greatly uncertain.