El Niño and climate change

Trenberth, Kevin E.; Hoar, T. J.

doi:10.1029/97gl03092

Cited by 440 publications

(264 citation statements)

References 13 publications

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“…The long duration of the early 1990s El Niño event is comparable to that of the early 1940s. Only by relaxing the El Niño threshold from the upper 30 percentile to the median does the early 1990s period appear as excessive as Trenberth and Hoar (1997) asserted. Independent of the threshold used, long-lived La Niña events have occurred through the full record.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

“…It is beyond the scope of this paper to discuss the complicated reasons that determine the duration of ENSO events, but the reader is referred to Eccles and Tziperman (2004), Kleeman (2008), andMacMynowski andTziperman (2008) that explore both linear and nonlinear mechanisms for this at length. Returning to the issue of the longest-lasting La Niña events in the sense of Trenberth and Hoar (1997), it is perhaps noteworthy that one of the three longestlasting runs below the MEI.ext median was completed just in this millennium (1998-2002: 43 months), while the other two occurred about a century ago: 1891-1895 (45 months), and 1907-1911 (46 months). However, all three of these La Niña-like conditions ended considerably sooner than the El Niño-like run of late 1989 into 1995.…”

Section: Spatial Features Of the Meiextmentioning

confidence: 99%

“…In the MEI.ext framework, the long-lived El Niño of the early 1990s was just as long as its lesser-known cousin of the early 1940s. This is noteworthy since the more recent El Niño has been used as evidence for anthropogenic climate change, also arguing that the recurrence interval of such a long-lived event could be well over 1000 years (Trenberth and Hoar, 1997). To be fair, Trenberth and Hoar, using Darwin SLP and Niño 3.4 SST, had looked at runs above the median of all values (50 percentile), the lowest possible threshold for El Niño events.…”

Section: Spatial Features Of the Meiextmentioning

confidence: 99%

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El Niño/Southern Oscillation behaviour since 1871 as diagnosed in an extended multivariate ENSO index (MEI.ext)

Wolter

Timlin

2011

Intl Journal of Climatology

954

696

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El Niño/Southern Oscillation (ENSO) remains the most important coupled ocean-atmosphere phenomenon to cause global climate variability on seasonal to interannual time scales. This paper addresses the need for a reliable ENSO index that allows for the historical definition of ENSO events in the instrumental record back to 1871. The Multivariate ENSO Index (MEI) was originally defined as the first seasonally varying principal component of six atmosphere-ocean (COADS) variable fields in the tropical Pacific basin. It provides for a more complete and flexible description of the ENSO phenomenon than single variable ENSO indices such as the SOI or Niño 3.4 SST. Here we describe our effort to boil the MEI concept down to its most essential components (based on SLP, SST) to enable historical analyses that more than double its period of record to 1871-2005. The new MEI.ext confirms that ENSO activity went through a lull in the earlyto mid-20th century, but was just about as prevalent one century ago as in recent decades. We diagnose strong relationships between peak amplitudes of ENSO events and their duration, as well as between their peak amplitudes and their spacing (periodicity). Our effort is designed to help with the assessment of ENSO conditions through as long a record as possible to be able to differentiate between 'natural' ENSO behaviour in all its rich facets, and the 'Brave New World' of this phenomenon under evolving GHG-related climate conditions. So far, none of the behaviour of recent ENSO events appears unprecedented, including duration, onset timing, and spacing in the last few decades compared to a full century before then.

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Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Section: Spatial Features Of the Meiextmentioning

confidence: 99%

Section: Spatial Features Of the Meiextmentioning

confidence: 99%

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El Niño/Southern Oscillation behaviour since 1871 as diagnosed in an extended multivariate ENSO index (MEI.ext)

Wolter

Timlin

2011

Intl Journal of Climatology

954

696

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“…Over the past few decades, an increased number of ElNino events have occurred relative to previous decades (Trenberth and Hoar, 1997;Mason, 2001). As El-Nino events are associated with a clockwise rotation of wave direction in the south-western Pacific Ocean (Goodwin, 2005), the increase in El-Nino events is responsible for the clockwise rotation in wave direction observed in this region, over the period 1980-2001 (Figure 10).…”

Section: Variability and Trends Of Global Wave Model Estimated Wave Ementioning

confidence: 98%

Variability and trends in the directional wave climate of the Southern Hemisphere

Hemer

Church

Hunter

2009

Intl Journal of Climatology

244

206

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The effect of interannual climate variability and change on the historic, directional wave climate of the Southern Hemisphere is presented. Owing to a lack of in situ wave observations, wave climate in the Southern Hemisphere is determined from satellite altimetry and global ocean wave models. Altimeter data span the period 1985 to present, with the exception of a 2‐year gap in 1989–1991. Interannual variability and trends in the significant wave height are determined from the satellite altimeter record (1991 to present), and the dominant modes of variability are identified using an empirical orthogonal function (EOF) analysis. Significant wave heights in the Southern Ocean are observed to show a strong positive correlation with the Southern Annular Mode (SAM), particularly during Austral autumn and winter months. Correlation between altimeter derived significant wave heights and the Southern Oscillation Index is observed in the Pacific basin, which is consistent with several previous studies. Variability and trends of the directional wave climate are determined using the ERA‐40 Waves Re‐analysis for the period 1980–2001. Significant wave height, mean wave period and mean wave direction data are used to describe the climate of the wave energy flux vector. An EOF analysis of the wave energy flux vector is carried out to determine the dominant modes of variability of the directional seasonal wave energy flux climate. The dominant mode of variability during autumn and winter months is strongly correlated to the SAM. There is an anti‐clockwise rotation of wave direction with the southward intensification of the Southern Ocean storm belt associated with the SAM. Clockwise rotation of flux vectors is observed in the Western Pacific Ocean during El‐Nino events. Directional variability of the wave energy flux in the Western Pacific Ocean has previously been shown to be of importance to sand transport along the south‐eastern Australian margin, and the New Zealand region. The directional variability of the wave energy flux of the Southern Ocean associated with the SAM is expected to be of importance to the wave‐driven currents responsible for the transport of sand along coastal margins in the Southern Hemisphere, in particular those on the Southern and Western coastal margins of the Australian continent. Copyright © 2009 Royal Meteorological Society

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“…To date, ENSO reconstruction efforts have tended to focus on only one aspect of the ENSO phenomenon, commonly the SOI, which only partially characterises the entirety of ENSO perturbations. Considerable research has also focused on the oceanic Niño 3 region SSTs (D' Arrigo et al, 2005;Evans et al, 2002;Latif et al, 2001;Mann et al, 1998;Timmermann, 1999), despite the fact that in recent years it has become apparent that the key region for coupled atmospheric-oceanic interactions involved in ENSO is located further west than traditionally defined by eastern Pacific ENSO zones (Trenberth, 1997;Trenberth and Hoar, 1996;Trenberth and Hoar, 1997;Wang, 1995).…”

Section: Rationalementioning

confidence: 99%

Classification of synchronous oceanic and atmospheric El Niño-Southern Oscillation (ENSO) events for palaeoclimate reconstruction

Gergis

Fowler

2005

Int. J. Climatol.

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Since the mid-1970s, ENSO has changed in character to a predominance of El Niño conditions, the extreme phase of which appears coincidental with increases in global temperature records. Instrumental time series (<150 years) are too short to adequately address the significance of late twentieth-century ENSO variability, thus, multi-century palaeoclimate reconstructions derived from long proxy records are sought. Despite the global influence exerted by ENSO on society, limited consensus exists within the scientific community as to which index best defines the timing, duration and strength of events. Here we address issues associated with the complexity of ENSO characterisation by comparing the 'event capture' ability of two currently used indices of ENSO. It is suggested that the use of a sole ENSO index is undesirable as a given index is only indicative of one physical aspect of the phenomenon, and as such is unlikely to be representative of the wider interactions experienced in the coupled ocean-atmospheric system. In an attempt to describe more of the nature and evolution of ENSO events, the Coupled ENSO Index (CEI) classification scheme was devised to identify synchronous oceanic (Niño 3.4 SST) and atmospheric (Southern Oscillation Index) anomalies associated with ENSO for the instrumental period . The CEI is of practical relevance to the ENSO community as it provides an amplitude preserving instrumental baseline for the calibration of proxy records to reconstruct both components of the ENSO system. Analysis of the nature of instrumental ENSO events from the CEI suggests that the frequency and intensity of post-1970 ENSO events (when 50% of all extreme events identified occur) appears the most anomalous in the context of at least the past century. It is hoped that the CEI will facilitate palaeo-ENSO research to systematically resolve the long-term context of past ENSO behaviour to assess whether the apparently anomalous nature of late twentieth-century variability is unprecedented within existing palaeoclimate archives.

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El Niño and climate change

Cited by 440 publications

References 13 publications

El Niño/Southern Oscillation behaviour since 1871 as diagnosed in an extended multivariate ENSO index (MEI.ext)

El Niño/Southern Oscillation behaviour since 1871 as diagnosed in an extended multivariate ENSO index (MEI.ext)

Variability and trends in the directional wave climate of the Southern Hemisphere

Classification of synchronous oceanic and atmospheric El Niño-Southern Oscillation (ENSO) events for palaeoclimate reconstruction

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