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ENSO Change in Climate Projections: Forced Response or Internal Variability?
Author(s) -
Maher N.,
Matei D.,
Milinski S.,
Marotzke J.
Publication year - 2018
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 - 10.1029/2018gl079764
Subject(s) - el niño southern oscillation , climatology , ensemble average , amplitude , environmental science , range (aeronautics) , climate model , variance (accounting) , multivariate enso index , coupled model intercomparison project , ensemble forecasting , climate change , oscillation (cell signaling) , atmospheric sciences , meteorology , southern oscillation , geology , physics , oceanography , materials science , accounting , quantum mechanics , biology , business , composite material , genetics
Two large ensembles are used to quantify the extent to which internal variability can contribute to long‐term changes in El Niño‐Southern Oscillation (ENSO) characteristics. We diagnose changes that are externally forced and distinguish between multi‐model simulation results that differ by chance and those that differ due to different model physics. The range of simulated ENSO amplitude changes in the large ensemble historical simulations encompasses 90% of the Coupled Model Intercomparison Project 5 historical simulations and 80% of moderate (RCP4.5) and strong (RCP8.5) warming scenarios. When considering projected ENSO pattern changes, model differences are also important. We find that ENSO has high internal variability and that single realizations of a model can produce very different results to the ensemble mean response. Due to this variability, 30–40 ensemble members of a single model are needed to robustly compute absolute ENSO variance to a 10% error when 30‐year analysis periods are used.