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Global warming and the El Niño Southern Oscillation

What the science says...

Select a level... Basic Intermediate

The El Nino Southern Oscillation shows close correlation to global temperatures over the short term. However, it is unable to explain the long term warming trend over the past few decades.

Climate Myth...

It's El Niño

"Three Australasian researchers have shown that natural forces are the dominant influence on climate, in a study just published in the highly-regarded Journal of Geophysical Research. According to this study little or none of the late 20th century global warming and cooling can be attributed to human activity. The close relationship between ENSO and global temperature, as described in the paper, leaves little room for any warming driven by human carbon dioxide emissions. The available data indicate that future global temperatures will continue to change primarily in response to ENSO cycling, volcanic activity and solar changes." (Climate Depot)

The paper claiming a link between global warming and the El Niño Southern Oscillation (ENSO)  is Influence of the Southern Oscillation on tropospheric temperature (McLean 2009). What does the paper find? According to one of it's authors, Bob Carter,

"The close relationship between ENSO and global temperature, as described in the paper, leaves little room for any warming driven by human carbon dioxide emissions."

In other words, they claim that any global warming over the past few decades can be explained by El Niño activity.

How do they arrive at this conclusion? They begin by comparing satellite measurements of tropospheric temperature to El Niño activity. Figure 1 plots a 12 month running average of Global Tropospheric Temperature Anomaly (GTTA, the light grey line) and the Southern Oscillation Index (SOI, the black line).

Figure 1: Twelve-month running means of SOI (dark line) and MSU GTTA (light line) for the period 1980 to 2006 with major periods of volcanic activity indicated (McLean 2009).

The Southern Oscillation Index shows no long term trend (hence the term Oscillation) while the temperature record shows a long term warming trend. Consequently, they find only a weak correlation between temperature and SOI. Next, they compare derivative values of SOI and GTTA. This is done by subtracting the 12 month running average from the same average 1 year later. They do this to "remove the noise" from the data. They fail to mention it also removes any linear trend, which is obvious from just a few steps of basic arithmetic. It is also visually apparent when comparing the SOI derivative to the GTTA derivative in Figure 2:

Figure 2: Derivatives of SOI (dark line) and MSU GTTA (light line) for the period 1981–2007 after removing periods of volcanic influence (McLean 2009).

The linear warming trend has been removed from the temperature record, resulting in a close correlation between the filtered temperature and SOI. The implications from this analysis should be readily apparent. El Niño has a strong short term effect on global temperature but cannot explain the long term trend. In fact, this is a point made repeatedly on this website (eg - here and here).

This view is confirmed in other analyses. An examination of the temperature record from 1880 to 2007 finds internal variability such as El Nino has relatively small impact on the long term trend (Hoerling 2008). Instead, they find long term trends in sea surface temperatures are driven predominantly by the planet's energy imbalance.

There have been various attempts to filter out the ENSO signal from the temperature record. We've examined one such paper by Fawcett 2007 when addressing the global warming stopped in 1998 argument. Similarly, Thompson 2008 filters out the ENSO signal from the temperature record. What remains is a warming trend with less variability:

Figure 3: Surface air temperature records with ENSO signal removed. HadCRUT corrections by Thompson 2008, GISTEMP corrections by Real Climate.

Foster and Rahmstorf (2011) used a multiple linear regression approach to filter out the effects of volcanic and solar activity and ENSO.  They found that ENSO, as measured through the the Multivariate ENSO Index (MEI), had a slight cooling effect of about -0.014 to -0.023°C per decade in the surface and lower troposphere temperatures, respectively from 1979 through 2010 (Table 1, Figure 4).  This corresponds to 0.045 to 0.074°C cooling from ENSO since 1979, respectively.  The results are essentially unchanged when using SOI as opposed to MEI.

Table 1: Trends in  °C/decade of the signal components due to MEI, AOD and TSI in the regression of global temperature, for each of the five temperature records from 1979 to 2010.

table 3

Figure 7

Figure 4: Influence of exogenous factors on global temperature for GISS (blue) and RSS data (red). (a) MEI; (b) AOD; (c) TSI.

Like Foster and Rahmstorf, Lean and Rind (2008) performed a multiple linear regression on the temperature data, and found that although ENSO is responsible for approximately 12% of the observed global warming from 1955 to 2005, it actually had a small net cooling effect from 1979 to 2005.  Overall, from 1889 to 2005, ENSO can only explain approximately 2.3% of the observed global warming.

Ultimately, all the data analysis shouldn't distract us from the physical reality of what is happening to our climate. Over the past 4 decades, oceans all over the globe have been accumulating heat (Levitus 2008; Nuccitelli et al. 2012, Figure 5). The El Niño Southern Oscillation is an internal phenomenon where heat is exchanged between the atmosphere and ocean and cannot explain an overall buildup of global ocean heat. This points to an energy imbalance responsible for the long term trend (Wong 2005).

Fig 1

Figure 5: Land, atmosphere, and ice heating (red), 0-700 meter OHC increase (light blue), 700-2,000 meter OHC increase (dark blue).  From Nuccitelli et al. (2012),

Data analysis, physical observations and basic arithmetic all show ENSO cannot explain the long term warming trend over the past few decades. Hence the irony in Bob Carter's conclusion "The close relationship between ENSO and global temperature leaves little room for any warming driven by human carbon dioxide emissions". What his paper actually proves is once you remove any long term warming trend from the temperature record, it leaves little room for any warming.

Intermediate rebuttal written by dana1981

Last updated on 10 July 2015 by pattimer. View Archives

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Further reading

NOAA have a very useful resource ENSO Cycle: Recent Evolution, Current Status and Predictions which features recent ENSO activity as well as model predictions of ENSO activity in the near future.

Denial101x video


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Comments 1 to 25 out of 206:

  1. Great post. Another point - your Figure 1 shows the basic problem with this claim at a glance. The grey temperature line has a discernible upward trend, while the dark ENSO line does not. So ENSO doesn't match the warming trend, case closed. However, as the paper itself is behind a paywall, the key findings have been posted here, with the graph split into three at 1980 and 1995: With this split, the warming trend is much harder to spot. You can do the same thing with surface temps (NASA GISTEMP): GISTEMP 1958-2009 - trend is clear GISTEMP 1958-2009 in 3 slices - trend obscured A "trick" to "hide the incline" perhaps?
  2. Erl - for a warming trend, you have to increase the net energy on the planet. Where is the evidence of this in ANY ocean cycle. While the initiation point of an ENSO event remains tricky, (is it wholly a dynamical phenomena?), I would say that other aspects are now pretty well understood. I also note that "ENSO" emerges in climate models, and yet these models do not create temperature trends unless there is a forcing (like CO2 or solar) applied.
  3. scaddenup #2 My understanding is that ENSO, La Nina, AMO etc are internal re-distributions of heat energy around the globe - not overall gain or loss of heat from the Earth system to space by forcing imbalances.
  4. Ken. So do I but Erl apparently does not.
  5. Please read: Tell me this: What is responsible for the long term change in the differential pressure that drives the trade winds and tropical temperature?
  6. Continuing from #20 on the Goddard-is-cherrypicking-sea-level-data thread. The same statement was made as in #3 here: ENSO are, after all, cycles, which don't make much difference in the long term. However, as the familiar MEI graph shows, there seems to be a lot more red since about 1977 or so. From a fascinating model run made by Timmerman et al. 1999: The tropical Pacific climate system is thus predicted to undergo strong changes if emissions of greenhouse gases continue to increase. The climatic effects will be threefold. First, the mean climate in the tropical Pacific region will change towards a state corresponding to present-day El Nino conditions. It is therefore likely that events typical of El Nino will also become more frequent. Second, a stronger interannual variability will be superimposed on the changes in the mean state, so year-to-year variations may become more extreme under enhanced greenhouse conditions. Third, the interannual variability will be more strongly skewed, with strong cold events (relative to the warmer mean state) becoming more frequent. If I read that correctly, sounds like more red overall with the occasional deeper blue.
  7. Isn't the El Nino Southern Oscillation showing a long term trend towards stronger and more frequent El Ninos because of global warming? Because I read a myriad of studies suggesting this. But in recent years that trend seems to be dissipating or is too short of a time period to make any meaningful judgements? Is this trend towards stronger and more frequent El Ninos truly manifesting itself or is it just a fluke of nature?
  8. #7: "I read a myriad of studies suggesting this." It would be helpful if you would provide some references, rather than just 'a myriad.' "But in recent years that trend seems to be dissipating or is too short of a time period to make any meaningful judgements?" Look at the graph in #6. What 'trend seems to be dissipating' are you referring to? Also note the 2nd and 3rd points from the Timmerman paper: - year-to-year variations may become more extreme and - with strong cold events (relative to the warmer mean state) becoming more frequent. Or to put it in terms of a 'forecast': Continued warming with a 30% chance of occasional heavy snow in some areas. 50% chance of record droughts and/or record flooding. 95% chance of skeptics refusing to look at the long term and seizing on minimal data to say 'No its not!' 100% chance of inaction on the part of the US government.
  9. I would like to see an article where the ENSO argument of Bob Tisdale is being countered. The ENSO argument presented here is not the main skeptical argument on ENSO, after all. Tisdale is going further, claiming that the NINO3.4 index does not fully account for ENSO as a process. He purports to show that when the entire set of processes involved in the progression of the ENSO phenomenon is included, the ENSO IS able to explain global warming since the mid 70s. I would like to see you tackle HIS argument to show specifically where it fails. In my opinion, this site would not be complete without such an article.
  10. Kayell, If any real people took Tisdale's argument seriously, then this site would tackle it. This site is not, however, required to tackle every bit of nonsense generated by every person on earth. The fact that Tisdale's cr@p gets play on WUWT is meaningless (and says a lot about WUWT and its readership). Those people are lost, and will stay lost. For what it's worth, however, Tisdale's entire collage of nonsense fails on one basic point, the First Law of Thermodynamics. From where does the energy come that allows ENSO to heat the planet? Put another way, ENSO has been around for thousands of years. Why, suddenly, now, does each successive El Nino warm the planet (which is actually the opposite, La Nina's warm the planet), while La Nina's have no counteracting effect? Why is heat suddenly accumulating now due to ENSO, yet never before today? What's changed? What is the physical mechanism at work? And before you ask, no, I haven't paid good money to read his cr@ppy theories, and I won't. If you'd like to send a PDF of his nonsense, and if I decide I'm willing to waste a chunk of my life looking at it, then it can maybe discussed (although, really, I'd rather spend my time looking at real science that is going to affect the course of policy, not sideline nutjobbery that is really of no consequence to anything). Short of that... no, I don't see the need for SkS to debunk every bit of Galilean look-at-me-I've-got-it-I'm-a-genius nonsense that exists in the world.
    Response: [Dikran Marsupial] Please keep the discussion to the science and avoid inflamatory terms, regardless of the perceived provocation.
  11. Wow, that was really quite an aggressive response, I must say. Where did that come from? You keep calling his ENSO argument 'crap' and 'nonsense'. And yet you admit you haven't actually read what he says, what his argument in full is all about. Sounds like pure reflexive dismissal to me. If this is such a nutcase piece of hypothesizing, then it should be exceedingly easy to actually show specifically where it fails. Your 1st law of thermodynamics counter-argument is of course only based in you not having read what he says of the matter. You know, I know and he knows where the energy is coming from. You know, I know and he knows how the Pacific uptake of solar energy varies wildly between La Niña and El Niño conditions.
    Response: [Dikran Marsupial] Please can EVERYBODY keep the discussion even tempered, or I will start deleting posts.

    Kayell: I suspect the tone of the reply was prompted by the rhetorical tone of your initial post "In my opinion, this site would not be complete without such an article. ". If you keep your posts purely scientific and avoid rhetoric you will find you get a much better response. If you want an argument addressed, then at least provide a link to where the argument is presented. If you know where the energy is coming from, then you ought to be in a position to debunk the argument yourself.
  12. Kayell, I'm not paying good money to Tisdale to read his nonsense. Period. [snip] [Why do you think it is that no-one except for WUWT regulars are paying any attention to his theory?]
    Response: [Dikran Marsupial] Discussion of motivations snipped. Please lets just keep this to the science, and wait and see if Kayell can come back with a more substantive description of the argument.
  13. Presumably Tisdale shows that ENSO's influence has become far more extreme over the past few decades, that it is unleashing astounding quantities of formerly stored and hidden energy? Does he explain how that works? Or does the hypothesis only work if explained in isolation from other evidence? For instance, the overwhelming balance of evidence indicates that Arctic sea ice is going through area excursions and persistent volume loss in a way that's very unusual and likely not to have taken place for many thousands of years. For this to happen requires some input of additional heat energy to the Arctic Ocean and indeed other measurements confirm that's the case. Given the timeline of Arctic sea ice behavior, integrating these observations of sudden change with Tisdale's approach requires some mechanism that could sequester energy for many thousands of years and then suddenly release it. How does that work? As we all know, energy in the form of heat is very difficult to keep in one place. So what's the storage mechanism for Tisdale's energy?
  14. Kayell - Tisdale's argument appears to be that the ENSO is not symmetric, that La Nina absorbs more energy than El Nino releases, and thus the heat content of the Earth rises in 'steps'. Problems with his hypothesis: * Why would the ENSO be asymmetric now, when it hasn't been for the last few hundred years - effects require causes and mechanisms, and he has proposed nothing plausible in that regard. * The oceans and the atmosphere have warmed, especially over the last 40 years - and given the Stefan-Boltzmann relationship of emitted power with temperature, if the atmosphere was radiatively unchanged we would have a negative (cooling) top of atmosphere (TOA) balance. The evidence shows a postive balance (less leaving than arriving), thus contradicting Tisdale. This is a major problem with any number of 'skeptic' theories. * His evidence (what there is of it) consists of extremely short "step" changes of sea surface temperatures - and as has been discussed here and elsewhere (as in the Escalator graphic), those are artifacts of noisy data and statistically insignificant short term trends. * Observed warming (25*10^22 Joules over the last 40 years in the top 2000 meters of the oceans) has occurred in a fairly steady rise. Not by "steps". * His statistics, if you can call them that, are terrible - he doesn't know enough to numerically support his hypotheses, and what he presents actually contradicts his ideas if you actually know what the numbers mean. --- In short, Tisdale's hypotheses consist of handwaving over statistically meaningless short periods and changes. None of it has been peer-reviewed, he is clearly not familiar with the body of peer-reviewed science and data on the issue, it's unsupported and unsupportable pixie dust. And it's rather frustrating to see such nonsense taken seriously by anyone, let alone be pushed repeatedly by Tisdale in his insulting and accusatory terms (multiple accusations of deception, conspiracy, data manipulation, etc). Hence the impatience from those who know anything about the ENSO and global warming...
  15. Kayell - "...claiming that the NINO3.4 index does not fully account for ENSO as a process..." I find this a very curious strawman argument. The NINO3.4 index is one measure (of many) of an acyclic process - consisting of wind driven changes in ocean overturn and hence heat exchange with the atmosphere. That index is not the process. I cannot think of anyone who has claimed it is (hence the strawman). It is, rather, one measure of that process, much as GDP is one measure of economic activity. If the ENSO index is insufficient to track the process, then what ENSO aspects does Tisdale think have changed in the 1970's? And why? How would he measure that, in a statistically significant fashion - where is his evidence? His favorite measure, sea surface temperature changes in various regions, is actually part of the NINO3.4 index; he's presented nothing new. As I said at the start, attacking the index is a Strawman Fallacy. The ENSO can be measured/tracked with trade winds, with atmospheric pressures (Southern Oscillation Index, SOI), or with sea surface temperatures (as in the NINO3.4 index). If Tisdale thinks these are insufficient, it is on him to present evidence of supportable process changes that have diverged from historic behaviors. He has not.
  16. Sphaerica - "Put another way, ENSO has been around for thousands of years" ENSO has been around for millions of years. There are enough people responding to Kayell, so I'll stay out of this.
  17. Frankly, I would think you would pounce on the opportunity to rip this particular ’skeptical’ argument apart, to present a clinical, blow-by-blow refutation of it. It is (still in MY opinion, though) the most robust, cohesive skeptical argument AGAINST an anthropogenic and FOR a natural cause of global warming out there. And it’s getting more and more traction amongst ’the skeptical crowd’. So it is indeed a real, important and relevant skeptical argument. It is an easy to grasp argument, mostly descriptive actually, and does not make use of any models or sets of novel assumptions, only available data. The physical mechanisms at work and their effects are readily observable through space and time and well known and described in the geophysical literature. In a way the argument explains itself once you understand the processes at hand and simply track the energy through the Earth system by looking at the various sets of data. If you’ll let me, I would be happy to give you a compendious summary of the argument.
    Response: [DB] As noted by Phippe and KR below, the skeptical thing to do would be to first address those questions already put to you on this thread. Those genuinely interested in advancing the scientific understanding should feel that to be an imperative.
  18. Kayell, why don't you start by adressing the robust, cohesive relevant critics to the very premise of that argument that have already been presented above by various contributors? That would be a necessary first step. Also, keep in mind that here we concern ourselves with scientific arguments that are supported by peer-reviewed scientific litterature; Tisdale's piece not only doesn't fit that description but also betrays a lack of familiarity with the relevant scientific litterature by its author. There is no doubt that the "argument" will gain traction among those with little scientific literacy on the subject, especially if they're frantically looking for any old useable bit to confirm what they want to believe. It doesn't make it better than any other argument that particular public will buy.
  19. Kayell / Kristian - I believe I have discussed Tisdale's arguments in some detail. I would be interested in any comments you might have on the lack of statistical significance of his "step" time periods, the positive (increasing energy) TOA balance that directly contradicts his ENSO attribution of global warming, the fact that sea surface temperatures (SST's) he argues from are actually included in both the NINO3.4 index and the MEI, etc. Well? What processes does Tisdale point to, processes that for some reason have changed from their many 10's of thousands of years history to suddenly warm the earth over the last 150? You know, evidence? Please point to data supporting your assertions, as per the opening post. (I'm afraid I will not take hand-waving very seriously...)
  20. Philippe Chantreau and KR, Since people here so far haven't adressed the actual argument at all, only their strawman versions of it, I see no reason spending time answering their/your appararent objections. Rather I would prefer presenting the argument. Dikran, are you seriously asking me to answer all these 'objections' to the argument before I actually describe the argument to you? That's a strange way of advancing a discussion ...
    Response: [Dikran Marsupial] Kayell, I am telling you to avoid rhetoric and instead stick to the science. If you want people to discuss Tisdales argument then either explain it in detail yourself, or provide a link to somewhere that does. The first law of thermodynamics is a perfectly good explanation of why Tisdales argument is wrong. If you have an objection then present it. If you continue to avoid discussing the science you will be making it clear that you are not interested in the answer to your questions and are merely trolling. The ball is in your court, I suggest you return it.
  21. Kayell / Kristian - If you feel I have incorrectly understood Tisdale's argument, perhaps you could (clearly) state what you feel his argument is? Or in some other fashion indicate what interpretive error you think has been made? ...without a statement of where you think the argument stands, it's absurd to claim that I (and others) have not addressed it. On my part, I believe I have addressed Tisdale's unsupported, and contradicted by evidence, hypotheses. Since you feel he's made a good argument, it falls upon you to state what that is, and why the various disagreements are (potentially) not valid. Barring that, I would (IMO) consider your posts so far on this thread to be assertions without evidence. "Rather I would prefer presenting the argument." By all means, please do.
  22. Kayell/Kristian - I said I'd stay out of this, but I've changed my mind. Bob Tisdale himself is unable to explain his hypothesis, so maybe you can have a shot at it? No one here is likely to waste one and a half hours watching his videos, so please explain to us what you find so compelling.
  23. For anyone interested, the discussion of the proposed mechanism starts at about 29:15.
  24. KR says: "By all means, please do." Thanks. That's all I'm asking for. I will. It'll take me more than five minutes though, and that's all I have to spare right now. So later.
    Response: [Dikran Marsupial] We will be patient, please do take time to present the argument carefully. I would recommend presenting it as a set of numbered steps that form the logical chain of the argument, I have found that works well in the past as then counter arguments can be discussed for each link in the chain separately in detail.
  25. Dikran says: "If you want people to discuss Tisdales argument then (...) explain it in detail yourself (...)" Exactly. I haven't yet presented it. [snip]
    Response: [Dikran Maruspial] You have been asked to present the argument, so please stop complaining about the tone of the discussion and present it so that we can have a productive discussion. I have snipped the remainder of your post so as not to distract further from discussion the science, if you want a positive reception then it is straightforward, stick to the science, regardless of perceived provocation.

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