Weak El Niños and La Niñas Come and Go from NOAA’s Oceanic NINO Index (ONI) with Each SST Dataset Revision

Back in April of this year NOAA added the 2014/15 El Niño to their Oceanic NINO Index (a.k.a. ONI). See the former version of ONI here. Last week, with NOAA’s switch to their new Extended Reconstructed Sea Surface Temperature dataset version 4 (ERSST.v4), the 2014/15 El Niño has now disappeared from their list of “official” El Niño and La Niña events. See the present (ERSST.v4) version of ONI here.

But the 2014/15 El Niño isn’t the only ENSO event to have disappeared from ONI with the change to the new ERSST.v4 dataset.  The 2005/06 La Niña also dropped off ONI, and so did the 1983/84 La Niña.  On the other hand, the 1967/68 La Niña and the 1979/80 El Niño became official ENSO events with the new ERSST.v4 data, where they weren’t qualified with the ERSST.v3b data.

The weaker, short-term El Niño and La Niña events (based on NINO3.4 region surface temperatures) appear and disappear from the NOAA Oceanic NINO Index with each revision and with changes in how anomalies are calculated for ONI.   Tables 1 and 2 include the 5 versions of NOAA’s Oceanic NINO Index that have existed over the past decade or so. (Click on them for larger versions.)  The ERSST.v3b data with the base years of 1971-2000 for anomalies are included on both tables.  The older versions of the Oceanic NINO Index are available through the Wayback Machine archives.

Table 1

Table 1

# # #

Table 2

Table 2

On Table 2, you’ll note that there are two Ocean NINO Indices using the ERSST.v3b data.  The left-hand ONI uses the base years of 1971-2000 for sea surface temperature anomalies, while the middle (and right-hand, ERSST.v4-based) ONI uses multiple climatologies that shift every 5 years.  Yes, that means that NOAA shifts the base years for anomalies every five years for ONI, meaning the anomalies are not referenced to a common base period.

NOAA discusses the reasoning behind this in their Description of Changes to Oceanic NINO Index (ONI) webpage, which was revised for the new ERSST.v4 data.  The first two paragraphs there read (my boldface):

Due to a significant warming trend in the Niño-3.4 region since 1950, El Niño and La Niña episodes that are defined by a single fixed 30-year base period (e.g. 1971-2000) are increasingly incorporating longer-term trends that do not reflect interannual ENSO variability. In order to remove this warming trend, CPC is adopting a new strategy to update the base period.

There will be multiple centered 30-year base periods that will be used to define the Oceanic Niño index (as a departure from average or “anomaly”). These 30-year base periods will be used to calculate the anomalies for successive 5-year periods in the historical record…

We discussed the flaw in their assumption that there had been a “significant warming trend in the Niño-3.4 region since 1950” in the June 2012 post Comments on NOAA’s Recent Changes to the Oceanic NINO Index (ONI).  In the real world, the “significant warming trend in the Niño-3.4 region since 1950” was a response to the 1976/77 Pacific Climate Shift, not some anthropogenic warming signal.  So NOAA deleted the effect of the 1976/77 Pacific shift with the change in how they calculate anomalies for ONI.

CLOSING

The Oceanic NINO Index has been referenced in numerous climate studies. How and if these multiple revisions have impacted those studies is for the authors to determine.  Sometimes, even after June 2012 when NOAA revised their method for calculating ONI, authors relied on the older version of the Oceanic NINO Index with the fixed base years of 1971-2000…like Trenberth et al. (2014) Earth’s Energy Imbalance.  In other words, even the climate science community appears not to have bought into using multiple base periods for an ENSO index.

And just in case you’re wondering, the 2014/15 El Niño would appear on ONI if NOAA had continued to use 1971-2000 for the base years with the new ERSST.v4 data.  Then again, NOAA has switched to the base years of 1981-2010 for many indices, so the 2014/15 El Niño would not exist in ONI with those base years using the new ERSST.v4 data.

The NOAA Oceanic NINO Index is used by some persons when they attempt to make claims about the causes of record-warm surface temperatures.  So expect there to be some alarmist nonsense about the absence of an El Niño in the 2014/15 season from the standard sources, including NOAA.

We discussed the reasons for the reported record warm global sea surfaces in the post Did ENSO and the “Monster” Kelvin Wave Contribute to the Record High Global Sea Surface Temperatures in 2014?     And as I’ll show in an upcoming post, the 2014/15 El Niño was stronger than most El Niño events during the satellite era if we look at the tropical Pacific as a whole.

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About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
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20 Responses to Weak El Niños and La Niñas Come and Go from NOAA’s Oceanic NINO Index (ONI) with Each SST Dataset Revision

  1. Pingback: NOAA: Doch kein El Niño 2014 – Schellnhuber ENSO-Prognose hat versagt | wobleibtdieglobaleerwaermung

  2. Easy come, easy go the global SST-data with NOAA… https://wobleibtdieglobaleerwaermung.wordpress.com/2015/06/22/noaa-doch-kein-el-nino-2014-schellnhuber-enso-prognose-hat-versagt/

    The MEI shows strong El Niño conditions with 1,6 in April/May 2015: http://www.esrl.noaa.gov/psd/enso/mei/comp.png
    “…The updated (April-May) MEI has risen by 0.61 standard deviations in one month to +1.57, for a high ranking above the ‘strong’ El Niño threshold (upper 10%ile). This is the highest MEI value in 17 years, surpassing the peak of the 2009-10 El Niño by a few 1/100…” http://www.esrl.noaa.gov/psd/enso/mei/

    Some ENSO-Models keep on predicting an Super El Niño 2015: http://iri.columbia.edu/wp-content/uploads/2015/06/figure42.gif

    But isn’t the IPWP-area at the surface and under water discharged and now to cool for such an Super-Event…? http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/weeklyenso_clim_81-10/wkd20eq2_anm.gif

    Cheers

  3. Thanks, Bob.
    I’m thinking; What will NOAA say when the temperatures drop after the 2014/15 El Niño ends?

  4. Bob Tisdale says:

    Andres, it looks like it will continue into 2016, making it the 2014/15/16 El Nino.

    Cheers.

  5. fhhaynie says:

    So they are now defining climate as a five year average rather than 30 year average. I think it is time for them to accept the fact that weather and climate are measure of the same processes and changes are cyclical on multiple time scales. Why not return to recording actual temperatures rather than anomalies?

  6. Thanks, Bob. Yes, NOAA thinks:
    “There is a greater than 90% chance that El Niño will continue through Northern Hemisphere fall 2015, and around an 85% chance it will last through the 2015-16 winter.”
    See ENSO Diagnostic Discussion – 11 June 2015, at
    http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_disc_jun2015/ensodisc.html

  7. Evan says:

    I might have a naughty opinion on recent change, but I wonder if they lowered ENSO “standard” a little bit to +/- 0.4ºC

  8. Alec aka Daffy Duck says:

    Bob, just something I saw today …

    24 June 2015

    Asymmetric impact of Atlantic Multidecadal Oscillation on El Niño and La Niña characteristics
    Abstract

    The long-lasting cold surface conditions of North Atlantic, i.e., the negative phase of Atlantic Multidecadal Oscillation (AMO), can intensify the El Niño–Southern Oscillation through the enhanced air-sea coupling under the increased central-to-eastern tropical Pacific mean sea surface temperature. However, the impact of warmer mean sea surface temperature (SST) is more efficient in the intensifying El Niño than La Niña, because of the nature of the exponential growth of atmospheric convection to SST change. Moreover, the farther eastward shift of the atmospheric convection during the negative AMO leads to the stronger El Niño due to the longer delayed negative feedback by oceanic waves. Therefore, the AMO mainly influences the El Niño intensity rather than La Niña intensity.

    http://onlinelibrary.wiley.com/doi/10.1002/2015GL064381/full

  9. Bob Tisdale says:

    Alec aka Daffy Duck, something seems off about that abstract. The negative AMO lasted from the early 1960s to the early 1990s, but the strongest East Pacific El Nino occurred in 1997/98, after the AMO had shifted to positive.

  10. Alec aka Daffy Duck says:

    Bob, when I read it my guess is they were says el ninos get an extra kick when AMO negative, which i inferred them meaning the reason there hasnt been any major strong el ninos since 97-98 is AMO was too warm and didn’t give the el ninos a boost.

    Just before the 1997-98 El Niño AMO did dip briefly… AMO with elnino time period of 97-98, 08-09 and current roughly highlighted http://woodfortrees.org/plot/esrl-amo/from:1996.6/to:2014.8/plot/esrl-amo/from:2014.75/plot/esrl-amo/from:1997.29/to:1998.4/plot/esrl-amo/from:2009.58/to:2010.33

  11. Pingback: The 2014/15 El Niño Was Not Focused on the Region Used By NOAA for their Oceanic NINO Index | Bob Tisdale – Climate Observations

  12. Pingback: The 2014/15 El Niño Was Not Focused on the Region Used By NOAA for their Oceanic NINO Index | Watts Up With That?

  13. Pingback: June 2015 ENSO Update – Tropical Pacific Approaching the Threshold of a Strong El Niño | Bob Tisdale – Climate Observations

  14. Pingback: June 2015 ENSO Update – Tropical Pacific Approaching the Threshold of a Strong El Niño | Watts Up With That?

  15. Pingback: October 2015 ENSO Update – Comparisons with the Other Satellite-Era Multiyear El Niño | Bob Tisdale – Climate Observations

  16. Pingback: October 2015 ENSO Update – Comparisons with the Other Satellite-Era Multiyear El Niño | Watts Up With That?

  17. Pingback: How Strong Was That El Niño or La Niña? – No One Knows For Sure | Bob Tisdale – Climate Observations

  18. Pingback: How Strong Was That El Niño or La Niña? – No One Knows For Sure | Watts Up With That?

  19. Pingback: NOAA Has Resurrected the 2014/15 El Niño with Its Recent Changes to the Oceanic NINO Index | Bob Tisdale – Climate Observations

  20. Pingback: NOAA Has Resurrected the 2014/15 El Niño with Its Recent Changes to the Oceanic NINO Index | Watts Up With That?

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