El Niño-Southern Oscillation Myth 1: El Niño and La Niña Events are Cyclical

Guest post by Bob Tisdale

This is the first of a series of posts that address many of the myths and misunderstandings about the tropical Pacific processes that herald themselves during El Niño and La Niña events. Most of the content will be chapters from my recently published ebook Who Turned on the Heat?

For almost 4 years, my presentations about the long-term effects of El Niño and La Niña events indicate the global oceans over the past 30+ years have warmed naturally. This puzzles many proponents of anthropogenic global warming. They see the often-used name for the coupled ocean-atmosphere process—El Niño-Southern Oscillation (ENSO)—and assume the processes are oscillatory or cyclical. They will then post a comment to the effect of:

What part of oscillation don’t you understand?

Or

Haven’t you ever heard of the ENSO cycle? El Niño and La Niña are parts of a cycle. How can a cycle cause long-term global warming?

Comments like that are the first clue their authors are arguing from ignorance; that is, they have no understanding of the subjects being discussed—none whatsoever.

First off, it indicates those persons have never examined an ENSO index, such as the sea surface temperature anomalies of the NINO3.4 region—an area along the eastern equatorial Pacific bordered by the coordinates of 5S-5N, 170W-120W. ENSO indices are used to indicate how often El Niño and La Niña events happen, how strong they were, and how long they lasted. If El Niño and La Niña events were cyclical, they’d transition between El Niño and La Niña then back to El Niño and on to La Niña again, and so on. But they don’t cycle between El Niños and La Niñas. There can be back-to-back and back-to-back-back El Niño conditions without La Niña conditions appearing between them. See Figure 1. And there can be the double-dip La Niñas, like we’ve experienced recently.

Figure 1

Part of the confusion stems from the term El Niño-Southern Oscillation, which is really the combination of two names. Some of the confusion stems from the attempts of climate modelers who often treat the processes of ENSO as cycles in their failed attempts to simulate ENSO.

CHAPTER 2.1 DO THE WORDS “OSCILLATION” AND “CYCLE” IN THE NAMES “EL NIÑO-SOUTHERN OSCILLATION AND “ENSO CYCLE” CAUSE MISUNDERSTANDINGS?

The words oscillation and cycle are used to describe the processes of El Niño and La Niña events as a single phenomenon. The commonly used term ENSO stands for El Niño-Southern Oscillation. The seemingly redundant term ENSO Cycle (El Niño-Southern Oscillation Cycle) is also used often. Many persons assume because cycle and oscillation are used to describe El Niño and La Niña that the two states oppose and offset one another, that a La Niña will counteract an El Niño. Bad assumptions. They definitely do not work that way.

The most obvious difference between the two states, which we discuss in Sections 1 and 3, is, El Niño events randomly release vast amounts of warm water from below the surface of the west Pacific Warm Pool and spread it across the central and eastern equatorial Pacific, but the reverse does not occur during La Niña events.

Are El Niño and La Niña events cyclical or oscillatory? Some parts are, and some parts aren’t. We’ll discuss this further in Chapter 4.17 ENSO – A Cycle or Series of Events?

AN OVERVIEW OF THE TERMS EL NIÑO-SOUTHERN OSCILLATION AND ENSO CYCLE

El Niño-Southern Oscillation is the combination of two names. The term is said to have been coined by Rasmussen and Carpenter in their (1982) paper Variations in Tropical Sea Surface Temperature and Surface Wind Fields Associated with the Southern Oscillation/El Niño. Let’s see what Rasmussen and Carpenter have to say about the individual components. Their Introduction begins with the term El Niño:

The interannual variability of sea surface temperature (SST) along the Peru-Ecuador coast is dominated by the El Niño phenomenon. The name El Niño was originally applied to a weak warm coastal current which annually runs southward along the coast of Ecuador around the Christmas season (Wyrtki 1975). In scientific usage, the term has now become more narrowly associated with the extreme warmings which occur every few years (Wyrtki 1979a), and which result in catastrophic effects on the ecological system of the region. In more recent years, Ramage (1975), Weare et al. (1976), and others have used the term to encompass the larger-scale features of the warming event; i.e., the upwelling area along both the equator and the South American coast.

A few paragraphs later, Rasmussen and Carpenter describe the Southern Oscillation after discussing some initial findings from as far back as 1897:

It remained, however, for Sir Gilbert Walker, in a classical series of papers (Walker, 1923, 1924, 1928; Walker and Bliss, 1930, 1932, 1937) to name the SO [Southern Oscillation] and describe the salient features of the surface pressure, temperature and precipitation fluctuations.

The full title of the first Walker paper is WALKER, G. T. (1923). Correlation in seasonal variations of weather. VIII. A preliminary study of world-weather. Memoirs of the Indian Meteorological Department 24(Part 4) 75–131.

These papers by Walker were not discussions of El Niño, however. The link between El Niño and the Southern Oscillation wasn’t established until the 1960s. Therefore, the word oscillation in Southern Oscillation does not apply to El Niño and La Niña events or their processes. It only applies to the impacts of El Niño and La Niña on the sea level pressures in Tahiti and Darwin, Australia.

The sequence of papers and the advancement in ENSO research is further described in Rasmussen and Carpenter (1982).

Then there’s the term “ENSO Cycle”. The NOAA Climate Prediction Center (CPC) and many others, including me, use the phrase to describe El Niño and La Niña events and the variations from one state to the other. Refer to the CPC’s wonderful series of ENSO-related web pages ENSO Cycle that we’ll use for further discussions in Chapter 4.14 Impacts of ENSO Events on Regional Temperature and Precipitation.

DEFINITIONS OF OSCILLATION AND CYCLE

The Wikipedia definition of Oscillation begins:

Oscillation is the repetitive variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states.

El Niño and La Niña events do not repeat in time, there are very few things that are repetitive in ENSO, so by this definition, ENSO isn’t a true oscillation. In fact, Wikipedia writes in their initial description of El Niño-Southern Oscillation.

El Niño/La Niña-Southern Oscillation, or ENSO, is a quasiperiodicclimate pattern that occurs across the tropical Pacific Ocean roughly every five years.

Oscillation is much easier to write than “quasiperiodic climate pattern”. To add confusion, “pattern” has multiple meanings. It could be used as “pattern in time”, or to describe a “spatial pattern”, as in the warming or cooling of the central and eastern equatorial Pacific.

Webster has a number of definitions for the word cycle. The one that fits ENSO best is:

1: a recurring series of events: as…

c : a series of ecological stages through which a substance tends to pass and which usually but not always leads back to the starting point <the cycle of nitrogen in the living world>

Because an El Niño event does not always lead to a La Niña event and because La Niña events can be followed by another independent La Niña event, this definition of cycle under “c” is applicable to ENSO.

The term Southern Oscillation is used to represent the effects of El Niño and La Niña on the sea level pressure of the off-equatorial South Pacific. We’ll discuss it further in Chapter 4.3 ENSO Indices. Also discussed in that chapter, there’s another widely used ENSO index. It represents the effects of El Niño and La Niña events on the sea surface temperature anomalies of the equatorial Pacific region called NINO3.4, which is bounded by the coordinates of 5S-5N, 170W-120W. The Southern Oscillation Index and NINO3.4 sea surface temperature anomalies do NOT represent the process of ENSO. They are used only to indicate the frequency, strength and duration of El Niño and La Niña events. They indicate nothing more. They do not represent the process of ENSO, only its effect on the variable being measured for the index.

RECAP

El Niño-Southern Oscillation and ENSO Cycle are convenient phrases used to describe El Niño and La Niña. El Niño and La Niña events are not repetitive in time so they are not true oscillations. If it’s understood that an ENSO cycle may not lead to another series of El Niño and La Niña events nor even lead to the opposite phase, then cycle is applicable.

It’s a lot easier to write El Niño-Southern Oscillation than it is to write El Niño-La Niña/Sea Level Pressure Difference Between Darwin and Tahiti Quasiperiodic Climate Pattern.

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CHAPTER 4.17: ENSO – A CYCLE OR SERIES OF EVENTS?

If you were to Google ENSO and cycle, you’d get over 700,000 results. Limit your search to Google Scholar and there are more than 39,000 results. Place “ENSO cycle” in quotes and there’s almost 5,800. One of the reasons: ENSO stands for El Niño-Southern Oscillation and oscillation implies cyclical behavior. Another reason: the delayed oscillator theory suggests that one phase leads to the next, and that sure sounds like a cycle. However, is ENSO really a cycle?

The need to treat ENSO as a cycle arises from the attempts to model ENSO with computers. Mother Nature, however, apparently isn’t concerned about our ability to model it. While parts of ENSO act as a cycle, the evolution of an El Niño event requires a basically random event to initiate it. Therefore, to answer the title question of this chapter, ENSO is a combination of the two.

Kessler (2002) Is ENSO a cycle or a series of events? discusses how observational data suggest that El Niño events are event-like disturbances, while other phases display the behavior of a cycle. The abstract reads:

After early ideas that saw El Niños as isolated events, the advent of coupled models brought the conception of ENSO as a cycle in which each phase led to the next in a self-sustained oscillation. Twenty-two years of observations that represent the El Niño and La Niña peaks (east Pacific SST) and the memory of the system (zonal-mean warm water volume) suggest a distinct break in the cycle, in which the coupled system is able to remain in a weak La Niña state for up to two years, so that memory of previous influences would be lost. Similarly, while the amplitude of anomalies persists from the onset of a warm event through its termination, there is no such persistence across the La Niña break. These observations suggest that El Niños are in fact event-like disturbances to a stable basic state, requiring an initiating impulse not contained in the dynamics of the cycle itself.

When studying this subject and looking for additional papers, it is important to isolate discussions of models and the efforts being taken to improve them. Models are not reality. They are attempts to simulate Mother Nature with computers. The discussion of whether ENSO is a cycle or a series of events is an observations-based discussion. Some of the model-based papers do include discussions of observations, but you have to make sure you’re basing your understandings of ENSO on the observations and not the models in those papers. That pretty much holds true for all climate and climate change papers.

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THE REST OF THIS SERIES

The remainder of this series of posts will be taken from the following myths and failed arguments. They’re from Section 7 of my book Who Turned on the Heat? I may select them out of the order they’ve been presented here, and I’ll try to remember to include links to the other posts in these lists as the new posts are published.

A New Myth – ENSO Balances Out to Zero over the Long Term

Failed Argument – El Niño Events Don’t Create Heat

Myth – ENSO Has No Trend and Cannot Contribute to Long-Term Warming

Myth – The Effects of La Niña Events on Global Surface Temperatures Oppose those of El Niño Events

Myth – El Niño Events Dominated the Recent Warming Period Because of Greenhouse Gases

Myth – ENSO Only Adds Noise to the Instrument Temperature Record and We Can Determine its Effects through Linear Regression Analysis, Then Remove Those Effects, Leaving the Anthropogenic Global Warming Signal

Myth – The Warm Water Available for El Niño Events Can Only be Explained by Anthropogenic Greenhouse Gas Forcing

Myth – The Frequency and Strength of El Niño and La Niña Events are Dictated by the Pacific Decadal Oscillation

And I’ll include a few of the failed arguments that have been presented in defense of anthropogenic warming of the global oceans.

Failed Argument – The East Indian-West Pacific and East Pacific Sea Surface Temperature Datasets are Inversely Related. That Is, There’s a Seesaw Effect. One Warms, the Other Cools. They Counteract One Another.

INTERESTED IN LEARNING MORE ABOUT THE EL NIÑO AND LA NIÑA AND THEIR LONG-TERM EFFECTS ON GLOBAL SEA SURFACE TEMPERATURES?

Why should you be interested? Sea surface temperature records indicate El Niño and La Niña events are responsible for the warming of global sea surface temperature anomalies over the past 30 years, not manmade greenhouse gases. I’ve searched sea surface temperature records for more than 4 years, and I can find no evidence of an anthropogenic greenhouse gas signal. That is, the warming of the global oceans has been caused by Mother Nature, not anthropogenic greenhouse gases.

I’ve recently published my e-book (pdf) about the phenomena called El Niño and La Niña. It’s titled Who Turned on the Heat? with the subtitle The Unsuspected Global Warming Culprit, El Niño Southern Oscillation. It is intended for persons (with or without technical backgrounds) interested in learning about El Niño and La Niña events and in understanding the natural causes of the warming of our global oceans for the past 30 years. Because land surface air temperatures simply exaggerate the natural warming of the global oceans over annual and multidecadal time periods, the vast majority of the warming taking place on land is natural as well. The book is the product of years of research of the satellite-era sea surface temperature data that’s available to the public via the internet. It presents how the data accounts for its warming—and there are no indications the warming was caused by manmade greenhouse gases. None at all.

Who Turned on the Heat?was introduced in the blog post Everything You Every Wanted to Know about El Niño and La Niña… …Well Just about Everything. The Updated Free Preview includes the Table of Contents; the Introduction; the beginning of Section 1, with the cartoon-like illustrations; the discussion About the Cover; and the Closing. The book was updated recently to correct a few typos.

Please buy a copy. (Credit/Debit Card through PayPal. You do NOT need to open a PayPal account.). It’s only US$8.00.

VIDEOS

For those who’d like a more detailed preview of Who Turned on the Heat? see Part 1 and Part 2 of the video series The Natural Warming of the Global Oceans. Part 1 appeared in the 24-hour WattsUpWithThat TV (WUWT-TV) special in November 2012. You may also be interested in the video Dear President Obama: A Video Memo about Climate Change.