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Global warming and the El Niño Southern Oscillation

What the science says...

Select a level... Basic Intermediate

El Nino has no trend and so is not responsible for the trend of global warming.

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)

At a glance

This particular myth is distinguished by the online storm that it stirred up back in 2009. So what happened?

Three people got a paper published in the Journal of Geophysical Research. It was all about ENSO - the El Nino Southern Oscillation in the Pacific Ocean. ENSO has three modes, El Nino, neutral and La Nina. In El Nino, heat is transferred from the ocean to the atmosphere. In La Nina, the opposite happens. So within ENSO's different modes, energy is variously moved around through the planet's climate system, but heat is neither added nor subtracted from the whole. As such, in the long term, ENSO is climate-neutral but in the short term it makes a lot of noise.

The paper (link in further details) looked at aspects of ENSO and concluded that the oscillation is a "major contributor to variability and perhaps recent trends in global temperature". First point, sure. Second point, nope, if you accept climate trends are multidecadal things, which they are.

That might have been the end of it had the authors not gone full-megaphone on the media circuit, promoting the paper widely in a certain way. "No scientific justification exists for emissions regulation", they loudly crowed. "No global warming", the denizens of the echo-chamber automatically responded, all around the internet. This is how climate science denial works.

Conversely, the way that science itself works is that studies are submitted to journals, peer-reviewed, then some of them get published. Peer review is not infallible - some poor material can get through on occasion - but science is self-correcting. So other scientists active in that field will read the paper. They may either agree with its methods, data presentation and conclusions or they may disagree. If they disagree enough - such as finding a major error, they respond. That response goes to peer-review too and in this case that's exactly what happened. An error so fundamental was found that the response was published by the same journal. The error concerned one of the statistical methods that had been used, called linear detrending. If you apply this method to temperature data for six months of the Austral year from winter to summer (July-December), it cannot tell you that during that period there has been a seasonal warming trend. So what happens if you apply it to any other dataset? No warming! Bingo!

A response to the response, from the original authors, followed but was not accepted for publication, having failed peer-review. At this point, the authors of the rejected response-to-the-response started to screech, "CENSORSHIP" - and the usual blogosphere battles duly erupted.

It was not censorship. Dodgy statistical techniques were picked up by the paper's highly knowledgeable readership, some of whom joined forces to prepare a rebuttal that corrected the errors. The response of the original paper's authors to having their errors pointed out was so badly written that it was rejected. That's not censorship. It's about keeping garbage out of the scientific literature.

Quality control is what it's all about.

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!

Further details

ENSO, the El Nino Southern Oscillation, is an irregular but well-understood phenomenon that affects the Eastern and Central Pacific Oceans. It is important both on a local and global basis, since it not only causes changes in sea-surface temperatures. It also affects the thermal profile of the ocean and both coastal and upwelling ocean currents.

Such changes can and do affect the diversity and abundance of important edible seafood species. Cold and warm-water forms are forced to migrate to where they find the conditions more to their liking. El Nino events in particular, where warm waters prevail close to the sea surface, can inflict a temporary loss of commercially important species of fish and squid from where they are traditionally fished. Some coastal communities along the Pacific seaboard of South America have a strong dependency on such fisheries. As such, prolonged El Nino conditions can be seriously problematic.

The warm El Nino mode of ENSO also affects global temperatures, as heat energy is transferred from ocean surface to the atmosphere. A strong El Nino is easily capable of raising temperatures above the upward slope that represents the change in radiative forcing caused by our increasingly vast greenhouse gas emissions - global warming, in other words. Conversely, the opposite to El Nino, La Nina, suppresses global temperatures. When several La Nina years occur in a row, climate science deniers are given the opportunity to insist that the world is cooling. This has happened before, most notably in the post-1998 period.

However, as fig. 1 shows, global temperature is rising independently of the short-term ENSO noise. Fig. 1 also shows that 2022 was the warmest La Nina year in the observational record. In fact, El Nino, La Nina and neutral years are all getting warmer.

Variations in ENSO in a warming world.

Fig. 1: variations in ENSO in a warming world. This plot therefore shows two independent phenomena that affect climate: the noisy ENSO and the underlying relentless upward climb in temperatures caused by our rapidly-increasing emissions of CO2 and other greenhouse gases. Temperature records typically get broken in El Nino years because the temperature is given an extra boost. 2016, a major El Nino year, held the global temperature record for a few years, but 2023 saw that record fall again. 2023 is in grey because that El Nino did not develop until later in the year. Graphic: Reaclimate.

The reader should by now be in no doubt about the difference between the long term global temperature trend caused by increased greenhouse gas forcing and the noise that shorter-term wobbles like ENSO provide. You would have seen something similar during the descents into and climbs out of ice-ages too. That's because ENSO has likely been with us for a very long time indeed. Ever since the Pacific Ocean came close to its present day geography, millions of years ago, it has likely been there.

The reader should by now be in no doubt about the difference between the long term global temperature trend caused by increased greenhouse gas forcing and the noise that shorter-term wobbles like ENSO provide. You would have seen something similar during the descents into and climbs out of ice-ages too. That's because ENSO has likely been with us for a very long time indeed. Ever since the Pacific Ocean came close to its present day geography, millions of years ago, it has likely been there.

Nevertheless, here we have something that warms the planet, even if that's on a temporary basis. As a consequence, some people with ulterior motives might just become interested. Over a decade ago now, that's what happened. A paper, 'Influence of the Southern Oscillation on tropospheric temperature' (Mclean et al. 2009) was published in the Journal of Geophysical Research. One of its co-authors, a well-known climate contrarian, commented:

"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."

If you enter the above quote, complete with its quotation marks, into a search engine, you will get lots of exact matches. Strange? Not really, if you have studied the techniques of climate science denial.

  1. a paper is published that barely mentions global warming.
  2. its authors go on to distribute slogans implying that they have put yet another Final Nail in the global warming coffin.
  3. right-wing media of all sorts from newspapers to blogs ensure wide distribution of the talking-points.
  4. individuals serve to fill in the circulation-gaps.

This is how it works, time and again. However, glaring errors were soon noticed in the paper, leading a group of specialists to offer a rebuttal, published in the same journal a year later (Foster et al. 2010).

Statistics is not everyone's cup of tea, but a very straightforward explanation of the key error was provided by Stephen Lewandowsky, writing at ABC (archived):

"This is best explained by an analogy involving daily temperature readings between, say, July and December anywhere in Australia. Suppose temperature is recorded twice daily, at midday and at midnight, for those 6 months. It is obvious what we would find: Most days would be hotter than nights and temperature would rise from winter to summer. Now suppose we change all monthly readings by subtracting them from those of the following month—we subtract July from August, August from September, and so on. This process is called "linear detrending" and it eliminates all equal increments. Days will still be hotter than nights, but the effects of season have been removed. No matter how hot it gets in summer, this detrended analysis would not and could not detect any linear change in monthly temperature."

Anyone can do this in Excel. First input a series of representative temperatures for the transition from Austral winter into summer:

Series of representative temperatures for the transition from Austral winter into summer.

Reasonable? OK, then let's plot them. Still looks like what we'd expect. It gets warmer in Australia from July to December and nights are usually colder than days, right?

Plot of temperatures

Now, let's do that detrending. This is what you get:

Detrended temperatures

As Lewandowsky pointed out in his ABC article:

"Astonishingly, McLean and colleagues applied precisely this detrending to their temperature data. Their public statements are thus equivalent to denying the existence of summer and winter because days are hotter than nights."

In other words: Fail.

Last updated on 24 March 2024 by John Mason. View Archives

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Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.

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 201 to 206 out of 206:

  1. "Could we experience an almost flat line in the air temperature to 2034 while the sea surface will continue to rise gently ?"

    ENSO is primary cause of the "wriggle" about a positive trend in surface temperatures. Whatever ENSO does, that trend (driven primarily by increasing GHG) will continue. Climate models have emergent ENSO-like feature but cannot predict what ENSO will do. They are good at picking the underlying trend however.

  2. If intensity of el niño is only directly proportional of the heat content store in the ocean near the equator pacific, then we should have bigger and bigger el niño until GHG is growing stopped. I'm already swelling ! 

  3. Max or not @202,

    I have to conclude that you have nothing to link the 18.6 year cycle of the lunar orbital plane to ENSO intensity other than the coincidence of 2015 seeing both a major El Niño and the 'minor lunar standstill' in that 18.6 year cycle and this coupled with the one previous major El Niño occurring 18 years earlier.

    Of course, the major cycle regarding tides is the metonic cycle which is 19.0 years in length. Yet if such tidal effects triggered El Niños, they would presumably be premature El Niño and thus minor El Niño.

    As for what drives the intensity of an El Niño, it is the warm pool accumulated in the western Pacific alone that provides the heat. It is a lessening of trade winds (roughly measured by SOI) coupled with the instability of the warm pool that triggers an El Niño and both of those are greatly influenced by the PDO. In a warming climate, it is surely the frequency  of major El Niño that is expected to increase, not the intensity of individual El Niños per se, although there is much still to learn on this mechanism. (See for instance Cai et al (2015) 'ENSO and greenhouse warming'.)

  4. Recommended supplemental reading:

    A new study finds a possible link between Arctic warming and more frequent El Niños in the Central Pacific.

    Dwindling Arctic Sea Ice May Affect Tropical Weather Patterns by Bob Berwyn, InsideClimate News, Jan 27, 2020

  5. Recommended supplemental reading:

    As the 2020–21 La Niña has come to an end, leaving us with neutral conditions in the tropical Pacific, we now wonder if we have seen the last of La Niña for a while or if we will see another dip into La Niña conditions by next fall. In the world of the El Niño-Southern Oscillation (ENSO), double-dipping is not a party foul—it’s actually quite common for La Niña to occur in consecutive winters (not El Niño, though). If you’re wondering why, then this is the blog post for you!

    Double-dipping: Why does La Niña often occur in consecutive winters? by Nat Johnson, ENSO Blog, NOAA's, May 27, 2021  

  6. Please note: a new basic version of this rebuttal was published on March 24, 2024 and now includes an "at a glance“ section at the top. To learn more about these updates and how you can help with evaluating their effectiveness, please check out the accompanying blog post @

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