NOAA’s Ever-Changing Definition of La Niña Years

UPDATE: I’ve added two illustrations to the end of the post. At the request of blogger “Kurt in Switzerland”, I plotted a comparison of the new and old versions of the Oceanic NINO Index data and posted it in a comment. I also plotted the difference, which is much more interesting. Both graphs have been added at the end of the post as suggested by blogger Gary Pearse.


There have been two changes in NOAA’s Oceanic NINO Index over the past year—not one—in addition to their monthly updates.

NOAA redefined their Oceanic NINO Index (ONI) last year. Prior to the change, they had used their ERSST.v3b-based NINO3.4 sea surface temperature anomalies with their standard base years 1971-2000. For the Oceanic NINO Index, the monthly NINO3.4 anomaly data is then smoothed with a 3-month filter and rounded to the closest 0.1 deg C value. The last few years of old version of the Oceanic NINO index are shown in Figure 1.

01 ONI Old

Figure 1

When they changed the Oceanic NINO Index last year, NOAA used a series of sliding base years to determine the anomalies. Their logic for the change was that sea surface temperatures in the NINO3.4 region were being impacted by human-induced global warming. That’s nonsense. As discussed in the post Comments on NOAA’s Recent Changes to the Oceanic NINO Index (ONI), NOAA failed to recognize that the increase in their NINO3.4 sea surface temperatures occurred as a result of the 1976 Climate Shift, and that NINO3.4 sea surface temperature anomalies for the periods Jan 1950-December 1975 and January 1977 to present both had negative trends. That, of course, indicated that the 1976 Climate Shift was the cause of the long-term warming in NINO3.4 region sea surface temperatures—not manmade greenhouse gases.

The January 4, 2013 version of the Oceanic NINO Index is shown in Figure 2.

02 ONI New 1-4-13

Figure 2

I’ve highlighted 2006 to show that the first three months of 2006 are now considered La Niña months, where with the old version they were not. Why is that important? NOAA defines whether a given year is an El Niño year or La Niña year based on the first 3 months of their Ocean Nino Index. The logic is, it takes 5 to 6 months for global surface temperatures to respond to El Niños. Refer to the opening paragraph of the Introduction to Trenberth et al (2002). They write:

Following an El Niño the global surface air temperature typically warms up by perhaps 0.1 deg C with a lag of ~6 months [Newell and Weare, 1976; Pan and Oort, 1983; Jones, 1989; Wigley, 2000]. In an exceptional event such as the 1997–1998 El Niño the amount exceeds 0.2 deg C. Christy and McNider [1994] and Angell [2000] show that the entire troposphere warms up with an overall lag of 5–6 months, but the lag is slightly less in the tropics and is greater at higher latitudes. Consequently, the empirical evidence suggests a strong diabatic component to El Niño–Southern Oscillation (ENSO).

NOAA then uses the definition of El Niño and La Niña years to determine if the most recent year was the warmest El Niño or La Niña year—as if that’s meaningful, especially when one considers their ocean heat content data and satellite-era sea surface temperature data both indicate the oceans warmed naturally.

The recent changes in their definition of El Niño and La Niña years caused some confusion at NOAA. They mistakenly identified 2012 as the warmest La Niña year in their 2012 State of the Climate Report. Refer to the post NOAA’s Definition and Data Contradict Their Claim That 2012 Was The Warmest La Niña Year.

A month or so later, NOAA then corrected their mistake. Refer to the post NOAA Corrects Their 2012 State of the Climate Report – 2012 Was NOT the Warmest La Niña Year on Record. In their correction, NOAA stated (my boldface):

In the most recent version of the dataset, using the newer base period methodology, 2006 and 2009 are now classified as La Niña years.

As you’ll note in Figure 2, the first 3 months of 2009 are not identified as La Niña months, and, therefore, according to the NOAA definition, 2009 as a year would not be considered a La Niña year. How can they now be saying it’s a La Niña year?

Between January 21, 2013—when I noted the error—and February 2013—when NOAA corrected the State of the Climate Report—NOAA had once again changed their Oceanic NINO Index. See Figure 3. Now 2009 is a La Niña year, based on the first 3 months of 2009 in the latest version of the Oceanic NINO Index.

03 ONI New 3-4-13

Figure 3

The Oceanic NINO Index didn’t change during the first 3 months of 2009—it was a change in the November 2008 value that caused the reclassification to a La Niña for that season. Recall, according to the NOAA definition, the Oceanic NINO Index value has to be at –0.5 deg C or cooler for five consecutive months (or what they call seasons since they’re looking at 3-month averages) for there to be an “official” La Niña.


If you’d like to verify the recent changes in the Oceanic NINO index, use the following http address…

…in the Wayback Machine. You’ll find that the recent changes impacted Oceanic NINO Index values over the entire term of the data.


First NOAA redefined how sea surface temperature anomalies should be calculated to account for a fictitious global warming signal in the NINO3.4 region. Then they conveniently forgot about their redefinition of La Niña years in the 2012 State of the Climate Report—then corrected the mistake long after the mainstream media has moved on to other ways to misinform the public about human-induced global warming. Now NOAA can’t seem to figure out how to determine El Niño and La Niña events based on their new definition.

If NOAA wants to stop confusing themselves, maybe they should switch back to the old version and forget this nonsensical new version of their Oceanic NINO Index.


As noted above, NOAA’s ocean heat content data and their satellite-era sea surface temperature data indicate the oceans warmed naturally, primarily in response to El Niño and La Niña events. For further information, refer to my illustrated essay “The Manmade Global Warming Challenge” (42MB), and to the two-part YouTube video series “The Natural Warming of the Global Oceans” (Part 1 and Part 2), and to my ebook Who Turned on the Heat? which is available in pdf form here for US$8.00.


Figure 4 is a comparison of the old and new versions of the NOAA Oceanic NINO Index.

Fgure 4 ONI Comparison

Figure 4

The difference between the old and new versions, Figure 5, is more informative. In my comment at WUWT, I wrote, After a long-term decrease, there’s a sudden shift in 1990. Then the difference plateaus (increases slightly) over the last 2 decades.

Figure 5 ONI Difference

Figure 5

In reality, before 1980 and working back in time, a gradually increasing upward bias (toward El Niño conditions) was added. Then there was a sudden downward bias (toward La Niña conditions) in 1990. The bias has been returning very slowly toward zero since then.

NOAA went to all that trouble to eliminate the effect of the 1976 climate shift, as discussed and illustrated in Comments on NOAA’s Recent Changes to the Oceanic NINO Index (ONI). In the end, NOAA has created a meaningless index.

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March 16, 2013 12:30 am

[snip . . OT . . mod]

March 16, 2013 1:00 am

This is interesting. The article is predicated on the absoluteness of a position that “NOAA failed to recognize that the increase in their NINO3.4 sea surface temperatures occurred as a result of the 1976 Climate Shift”
Now, given that NOAA scientists obviously disagree and see a need for their changes, this means there is scientific disagreement — that’s good — science advances by contestation. However, the article fails to engage with the opposing views rationale, and instead takes an emphatic position that of course they are wrong. That’s fine, but it doesn’t help without engaging with the reasoning of the counter position.
When there is contestation in the literature, rebuttle papers should not say “you’re wrong and I’m right, and this is why I’m right”. Rather, rebuttle papers should say “you’re wrong and I’m right, now let me examine *your* reasoning and show why your conclusion is invalid”.
That said, it’s rare to find an argument where one position is absolutely wrong and another absolutely right; almost invariably the outcome is really a mix of two positions. As is, I suspect, the case here … there probably is a mix of a climate shift and a background trend, and so there is a need to consider how to best integrate both perspectives in the construction of the index to the benefit of all.

NZ Willy
March 16, 2013 1:01 am

Looks like 2013 is shaping up to be a “La Nina” year too — observe negative temps. That means they can add an arbitrary warming signal to the “background”, right? \(cynic)

Kurt in Switzerland
March 16, 2013 1:12 am

Good eyes, Bob. Nice to know someone is minding the till.
It would be beneficial to make contact with NOAA, to hear “their side of the story.”
Kurt in Switzerland

Kurt in Switzerland
March 16, 2013 1:14 am

P.S. Could you post “before” & “after” in graphical format?
Kurt in Switzerland

Peter Miller
March 16, 2013 3:36 am

The new anomalies appear to be just over 0.1 degrees C less than the old anomalies, however the new, new anomalies have reversed part of this.
I guess that means someone at NOAA realised the historic average had been increased in the new anomalies – that is very unusual in ‘climate science’, where every new interpretation of historic data requires the past to be cooler than previously – so the new, new anomalies corrected at least part of this heresy.

Anthony H.
March 16, 2013 5:34 am

A man with one watch knows what time it is; a man with two watches is never sure.
-from an old joke book of supposed Chinese wisdom, but relevant here.

March 16, 2013 5:49 am

“As noted above, NOAA’s ocean heat content data and their satellite-era sea surface temperature data indicate the oceans warmed naturally, primarily in response to El Niño and La Niña events.”
What exact is the heat source in ‘nature’ that warmed oceans in response to El Niño and La Niña events?
Why there is a remarkable correlation between the solar neutrino capture rate and the Ocean Niña Index (ONI)?

Dave in Canmore
March 16, 2013 5:51 am

re: global warming affecting Niño3.4 SST
Wouldn’t people who study the ocean understand that the ocean temps determine the air temps and not the other way around? As far as I understand the few hundreths of a degree of warming in the air (whatever one thinks the cause is) can’t actually raise the water temperature as it is lost in the latent heat of vapourization?
Is high school science beyond these people or am I missing something?

Barry Cullen
March 16, 2013 7:26 am

As is being further revealed by Climategate 3.0, this obfuscation is just a continuation of “hide the decline”. Why do “adjustments/harmonizations” always seem to make older data colder and newer warmer?

March 16, 2013 7:47 am

So after their ‘adjustments’, they now show that 7 of the last 14yrs have been La Niña yrs, 1 of the last 14yrs has been an El Niño year & 6 have been neither?
Do they realize what this does to the alarmists’ claims that “increasing greenhouse-gas concentrations” cause “El Niño-like conditions”? re: Timmerman et al 1999 – ‘Increased El Niño frequency in a climate model forced by greenhouse warming’ (
It is additional evidence that 1) the models are faulty & incapable of depicting reality & predicting the future, 2) that their hypothesis that ghgs were causing changes in ENSO was wrong, and 3) that the natural ocean cycles contributed to the late 20th century warming.
Reminds me of the whack-a-mole game. A problem mole pops up, they whack it, & more problem moles that they had previously whacked down, pop up again.

March 16, 2013 7:48 am

My tax dollars at work: Some guy at NOAA dickering about with the numbers.
Are they trying to create the illusion that the cold La Ninas have less of a cooling effect, due to Global warming? It is not going to convince people, with the weather cycle moving back to the 1950’s pattern of snowstorms in March. ( Joe D’Aleo has a neat post about this cycle and the March snowstorms they used to have, on his WeatherBELL site.) Our forecast is for a foot of snow, up here in New Hampshire, next Tuesday. The snow may reach right down to the coast and clout Boston, in which case the ordinary guy on the street will be doubting the globe is warmer, though the Boston Globe is warmist.
In any case, thanks for the heads-up, Bob.

March 16, 2013 8:11 am

Bob Tisdale says:
March 16, 2013 at 5:26 am
Your graphs of difference, etc added in your responses should be moved up into the article. As Kurt in Switzerland thought, its most illustrative:
Kurt in Switzerland says:
March 16, 2013 at 1:14 am
P.S. Could you post “before” & “after” in graphical format?

Ian W
March 16, 2013 8:45 am

Dave in Canmore says:
March 16, 2013 at 5:51 am
re: global warming affecting Niño3.4 SST
Wouldn’t people who study the ocean understand that the ocean temps determine the air temps and not the other way around? As far as I understand the few hundreths of a degree of warming in the air (whatever one thinks the cause is) can’t actually raise the water temperature as it is lost in the latent heat of vapourization?
Is high school science beyond these people or am I missing something?

High school science knowledge of latent and specific heat, jobbing gardener knowledge of plant and tree growth, heating and air-conditioning engineer knowledge of humidity and enthalpy – yes these are all way beyond the capabilities of climate ‘scientists’ with PhDs and fellowships in august professional societies; especially when there is government money for grants and lecture circuit funding for an otherwise unremarkable ‘professor’ with poor grasp of statistics less of spreadsheets and no ethics.

nutso fasst
March 16, 2013 8:54 am

Surely there are NOAA employees reading this (a commenter to another thread is self-described as noaaprogrammer), and there must be someone at NOAA who bears responsibility for the changes. Who is the prime manipulator?

John F. Hultquist
March 16, 2013 8:55 am

Dave in Canmore says:
March 16, 2013 at 5:51 am
“. . . am I missing something?

Politics. Green agenda. Agenda 21. Redistribution of wealth. Your lack of guilt for being alive. What did I miss?
Volker Doormann says:
March 16, 2013 at 5:49 am
“What exact is the heat source in ‘nature’ that warmed oceans in response to El Niño and La Niña events?

The oceans are warmed by energy from the Sun entering the water when not obstructed by clouds. That warmed water is pushed and held in the Western Pacific ‘warm pool’ until Trade Winds weaken, and so on. Several of Bob T’s posts go into this in some depth. In this sense, the use of the phrase “in response to” is akin to hitching the team up facing the cart rather than the right-way-round.

John F. Hultquist
March 16, 2013 8:56 am

Sorry, Mod. I missed a / up there after “something”
[Reply: Fixed, I think. -ModE]

Arno Arrak
March 16, 2013 11:53 am

This is amusing. NOAA does not understand anything about the El Nino and now Tisdale whose theory about the El Nino is wrong tries to prove that a rival theory is wrong. What interests me most is affirmation that the Nino3.4 warming precedes atmospheric warming by about five months and that warming in the tropics is slightly ahead of warming elsewhere. This confirms my theory according to which the El Nino phenomenon is a harmonic oscillation of ocean water in the Equatorial Pacific. First, trade winds push warm water into Western Pacific where it piles up as the Indo-Pacific Warm Pool. Periodically gravity flow of piled-up water returns east along the equatorial counter-current as an El Nino wave, runs ashore in South America, spreads out north and south along the coast, and warms the air above. That is when we notice the warmth of an El Nino. But any wave that runs ashore must also retreat. As the El Nino wave retreats sea level behind it drops by half a meter, cold water from below is sucked up to fill this space, and a La Nina has started. Now it so happens that Nina3.4 observation post sits right smack in the middle of the equatorial countercurrent and watches all the El Nino waves go by. The time lag that everyone agrees is real is due to the fact that Nino3.4 catches the wave before it gets to South America. It is the time the El Nino wave needs to get from the middle of the Pacific Ocean to South American shores. It is that simple and has nothing whatsoever to do with global warming..

March 16, 2013 12:08 pm

Remember this Lubachenko’s NOAA. Whatever, the motive for these changes, be suspicious and suspect the worst. She is operating a minstry of truth with focus on oceanography, meteorology and climatology.

March 16, 2013 12:33 pm

Bob Tisdale says:
March 16, 2013 at 5:26 am
First, here’s a comparison of the old and new Oceanic NINO Indices:
Now, here’s the difference:
The comparison graphs look like a thumbtack was stuck in chart at the 1982 mark and rotated slightly counterclockwise to cool the historical and warm the present. It would be interesting to analyze the common trick of cooling the past and heating the recent records (GISS, NOAA) to see if they actually did do it this way.

March 16, 2013 1:20 pm

I just find it shocking that people at NOAA can tinker about with data, change records and make stuff up, and no one outside the skeptical world seems to give a [self-snip]. The MSM should be all over this with headlines like: WHAT THE F### IS GOING ON?!
The world is still wasting billions of $$$ thanks to reports that come out of organizations like this. It’s FRAUD. I just hope someone is taking names for the massive court cases coming up in the years not so far away anymore.

Bob Shapiro
March 16, 2013 1:33 pm

Is this another case of NOAA changing the numbers/procedures to get a “better” result? Are there many of these changes? Are there enough of these changes to make a case that NOAA is violating the law that requires thm to report their statistics honestly?

March 16, 2013 4:01 pm

Mannian Mathematics in play perhaps?
Or is it something as simple as incompetence ?
I lack the mathematical abilities to analyze some of the information presented here.
I do know, however, that if an accountant starts rewriting the past records of a company, he had better have VERY good reasons, or he might find himself on the wrong side of the law.

March 16, 2013 4:22 pm

Lying sacks of __________ { fill in the blank }.
Maybe, just maybe, budget cuts will force them to use one and only one reference.
It’s obvious that they are over funded if they have a shelf full of references that they can rummage through in order to find one that fits their desired narrative.

March 16, 2013 7:05 pm

Hello Bob,
I take your point, The climate warms, the climate cools. The only thing the climate can’t do is stay the same.
Since global temperatures were below average for most of the century, why do people assume the worse when temps go above average?
By definition, the average will never have all samples below average, there must be values above average as well.
Now that temperatures are declining, returning to average, weren’t people just getting worked up for nothing?……
I look forward to your next post

March 16, 2013 10:53 pm

Thanks Bob,
The AGW “working hypothesis” & associated consensus will continue to seek the ever dwindling donation dollars.
Their end is near, not because of media coverage, but put simply, NSF is out of our tax dollars here and overseas Phil & crew are eating crumbs:)

March 17, 2013 12:14 am

[snip . . OT . . mod]

March 17, 2013 6:53 am

I can hardly wait to see how hot 2006 will become by 2020.

Luther Wu
March 17, 2013 8:21 am

Skeptik says:
March 17, 2013 at 6:53 am
“I can hardly wait to see how hot 2006 will become by 2020.”
You get the Gold Star…

March 17, 2013 10:04 am

The changes Bob shows in fig. 4 show a rotation (anticlockwise) which reduces warming. Perhaps with the Marcott fiasco-scandal of yet another climate scientist caught data-fixing, this is the NOAA pre-emptively setting their house in order by removing some previous pro-warming adjustment. Maybe they sense a broom on the way.

Kurt in Switzerland
March 17, 2013 10:43 am

It is high time to officially inquire at the NOAA for an explanation of / justification for the adjustments.
Kurt in Switzerland

March 17, 2013 3:42 pm

The change is interesting, especialy comparison between old and new values. But it doesn’t necessarily have to be bad just because we don’t like it. The index is kind of pattern recognition/similarity task, isn’t it? Then improving the algorithm may actually bring changes such as this without any intended harm.
It is you who always says that temperature change is driven mainly by the El Nino / La Nina conditions, so I wonder how this correlation goes with the old and new data. Something tells me the new data may actually provide better correlation than old…

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