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Teaching old indices new tricks: A state‐space analysis of El Niño related climate indices
Author(s) -
Mendelssohn Roy,
Bograd Steven J.,
Schwing Franklin B.,
Palacios Daniel M.
Publication year - 2005
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 - 10.1029/2005gl022350
Subject(s) - el niño southern oscillation , climatology , sea surface temperature , amplitude , environmental science , series (stratigraphy) , multivariate enso index , term (time) , pacific decadal oscillation , global warming , southern oscillation , index (typography) , oscillation (cell signaling) , la niña , climate change , oceanography , geology , physics , chemistry , paleontology , quantum mechanics , world wide web , computer science , biochemistry
State‐space models were applied to several climate indices associated with the El Niño–Southern Oscillation (ENSO), including the Southern Oscillation Index (SOI) and its component sea level pressure series; the NINO3 sea surface temperature index; and the Northern Oscillation Index (NOI). The best models for each series include a significant long‐term nonparametric trend combined with a stochastic stationary cyclic term that clearly delineates the El Niño and La Niña events. There is no evidence that the frequency of ENSO events has changed over the 20th century. The long‐term trend, however, has contributed to an apparent increase in the magnitude of recent El Niño events. This trend, potentially related to global warming, has increased the level of each series by an amount equal to 30–50% of the amplitude of their corresponding annual cycle or cyclic ENSO term. Thus, the background sea surface temperature in the eastern equatorial Pacific is more than 0.5°C warmer now than prior to 1950, implying a greater overall impact of El Niño events.