[See the two updates at the end of the post]
This paper claims that ENSO is a following rather than a forcing of climate, but given what we’ve seen in the last two decades, it sure seems like ENSO El Nino events are in fact a forcing of the global climate, from which the Earth quickly recovers.
The paper: (paywalled)
Changes in ENSO Activity During the Last 6,000 Years Modulated by Background Climate State
Soon‐Il An, Seul‐Hee Im, Sang‐Yoon Jun
Abstract
Various proxy records show that El Niño–Southern Oscillation (ENSO) activity has changed from calm to active during the last 6,000 years. However, it is so far unclear whether orbital forcing has solely induced such a dramatic change. In this study, we performed a transient run for the last 6,000 years using an Earth system model of intermediate complexity affected by orbital forcing only without changes due to other climate forcing, and then its time‐varying background states were implemented into an intermediate atmosphere‐ocean coupled model for ENSO. ENSO activity simulated by the intermediate atmosphere‐ocean coupled model during the last 6,000 years resembled the observed proxy data, inferring that orbital forcing mainly leads to changes in ENSO activity during the last 6,000 years. From additional sensitivity experiments, we found that a change in sea surface temperature background conditions is primarily responsible for the observed ENSO activity over the last 6,000 years through modifying the anomalous horizontal thermal advection of the mean SST gradient.
https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2017GL076250
UPDATE BY ANTHONY: Commenter “frankclimate” has provided a URL for the paper:
https://www.docdroid.net/QmS34GN/101002-at-2017gl076250.pdf
Reading it, it all makes sense now, thanks to that mighty big word “may”:
[Update by Willis Eschenbach]
I trust that Anthony won’t mind my noting that I’ve said for some time that the El Nino/La Nina pump is indeed a “following rather than a forcing of climate”, to use Anthony’s words. To be more precise, it is another temperature-regulating emergent phenomenon, one which occurs when the Pacific ocean temperature and surface heat content get above a certain level. At that point, the winds spring up and push millions of cubic metres of warm ocean water towards the poles, cooling the ocean. See my posts below for a fuller discussion.
Best to all, and thanks as always to Anthony for providing this marvelous forum for scientific discussion.
w.
The Tao of El Nino 2013-01-28
I was wandering through the graphics section of the TAO buoy data this evening. I noted that they have an outstanding animation of the most recent sixty months of tropical sea temperatures and surface heights. Go to their graphics page, click on “Animation”. Then click on “Animate”. When the new…
The Power Stroke 2014-02-27
I got to thinking about the well-known correlation of El Ninos and global temperature. I knew that the Pacific temperatures lead the global temperatures, and the tropics lead the Pacific, but I’d never looked at the actual physical…
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To me its always seem like ENSO was over rated in its important to climate. l pay little heed to it myself.
The reason why is because for me it has always made more sense to look for the answer to climate change through weather rather then anything else.
Because while we now view the LGM as climate, had we been living through it at the time then it would have simply been viewed as weather. So that been the case its always seem like the best question to ask is “what would the weather need to be doing to allow that to happen”.
Well thanks to this years weather l feel am now alot closer to the answering that question. lts what’s going on in and around the Arctic and how this is linked with the jet stream. ls a key to understanding how the weather moves the climate. Changes in the Earth’s orbit may provide the background to climate change, but its the weather that provides the detail.
The mantra of Climate Change is that CO2 causes warming by delaying the return of energy to space. Interestingly, the “build up” phase of the ENSO oscillation actually does exactly that, in much greater heat quantity than CO2 even pretends to, and that heat eventually finds its way to space just as any heat retained by CO2 does.. I would suggest that any heat retention by CO2 actually escapes on a daily (or rather, nightly) basis. Also, if the build up of Pacific heat is lost over a period of months following the outbreak of El NIno, then it suggests that heat transfer to deeper ocean levels is not a given consequence of increased insolation over shorter time frames.
The glacial period ended 9000 years ago. The oceans are still pretty cold. Vast amounts of heat move around down there very slowly and warm even more slowly. It takes a great deal of surface heating and a long, long time to move the needle on the enthalpy content of this system as the interactions between atmosphere and deep ocean are strongly limited by evaporation at the boundary layer. What we are experiencing in the recent past weather-wise is just a minor perturbation of atmospheric temperatures with no long term significance for mankind or the planet.
I suggest sending Michael Mann to the bottom of the ocean ( any ocean) with his tree ring math algorithm.
It is neither forcing nor following, these terms being commensurate with some human activity, and the closest we can get to description of observations from our own point of view. Nature has no language, we humans satisfy ourselves with our own clumsy terms. Numerically speaking, the Sun and Moon work together for climate, such that Sun is the engine and Moon holds the steering wheel, with other more distant extraterrestrial forces present but less relevant in contribution.
Essentially solar and lunar forces combine such that ~60 years gives us ~13 El Ninos, but even that constitutes a half-cycle that must be doubled to form the Solar Cycle. As the full SC is beyond a human lifetime it is of less predictive interest.
The 13, though, is interesting, being the “Moon’s number” in antiquity from the ancient world of the forbidden occult, outlawed by The Church which wished to distance people from the moon, lest they uncover some predictive (declination) quality to the seasons. El Nino, ENSO, the Humboldt current, etc, have been modern ways to essentially avoid investigation of the lunar component. Are we still held back by religious belief, which in modern form is Environmentalism?
Please allow for broad generalizations/simplifications made in the following argument.
I believe that the El Nino and La Nina phenomenon act as “forcing” agents upon the climate system in the sense that they regulate the rate of throughput of energy through the climate system via an initial heat-gain in the equatorial regions and an eventual heat-loss in the mid-latitudes.
THE ENSO SYSTEM [skip if you are familiar with the details of the mechanism]
If I am interpreting the work of Bob Tisdale correctly, the default ENSO condition is the neutral state i.e. neither a La Nina nor an El Nino event. In the neutral ENSO state, there is an active Walker-Circulation across the equatorial Pacific Ocean that maintains strong trade winds that blow from the east to west. These easterly winds support a pool of warm water in the western equatorial Pacific ocean and the Indonesian Archipelago. The system is feed by an upwelling of cold deep-ocean water from the Humbolt current along the western coast of South America. When the equatorial Pacific Ocean is in this state, the Nino 3.4 region (i.e. eastern equatorial Pacific) is generally free of cloud because of the strong high-pressure system associated with the Walker-circulation. This allows the climate system to accumulate considerable amounts of solar energy through the warming of the surface layers of the ocean. This warm water is driven in a westerly direction across the Pacific ocean to add to the Indonesian warm-pool.
The La Nino state develops when the Walker Circulation strengthens, producing a stronger high-pressure system off the coast of Peru and a stronger low-pressure system in the western equatorial Pacific. The resulting increase in pressure differential across the equatorial Pacific leads to a strengthening of the easterly trade wind strength. Hence, a La Nina event could be considered as an example of the ENSO neutral state on steroids. This leads to a further reinforcement of the recharge of warm water from the eastern to the western equatorial Pacific Oceans.
In contrast, the El Nino state develops when the Walker Circulation collapses, resulting in a weakening of the trade-winds blowing from the east. This removes the support holding the elevated pool of warm water in the western equatorial Pacific ocean, resulting in a sub-surface plume of warmer-than-normal water tunneling its way across the Pacific. This plume of warm water emerges in the eastern equatorial Pacific heralding the onset of an El Nino event. It is generally agreed that the subsequent El Nino event eventually re-distributes this warmer than normal water towards the mid-latitudes where heat is lost from the climate system by being re-radiated out into space.
MISTAKEN ASSUMPTIONS ABOUT THE ONSET OF EL NINO and LA NINA EVENTS
I believe that we have been mistakenly assuming that the onset of El Nino events and La Nina events are
directly related to one another.
Historically, there are many cases where moderate to strong El Nino events have not immediately (~ 1-2 years) been followed by La Nina events e.g. the 1982/83 and 1991/92 El Ninos.
This raises the hypothesis: “What if the onset of these two type of ENSO states were each driven by a different underlying mechanism.”
I contend that El Nino events are in fact triggered by lunar tidally-induced gravity waves that travel along the Earth’s Equator from East Africa out into the equatorial western Pacific Ocean. These traveling atmospheric gravity waves manifest themselves in the Earth’s atmosphere and oceans as Madden-Julian Oscillations. Roundabout every 4.5 years these Madden-Julian Oscillations start aggressively penetrating into the equatorial western Pacific Ocean setting off westerly wind bursts (WWB’s). It is these WWB’s that disrupt the Pacific trade winds that blow from the Walker circulation wind-pattern that is responsible for keeping holding back the western Warm Pool. Once the Walker Circulation collapses the warm water near Indonesia /Philipines sloshes across to the eastern equatorial Pacific ocean off Peru setting off an El Nino event.
http://astroclimateconnection.blogspot.com.au/2018/05/a-re-post-of-el-ninos-during-new-moon.html
In contrast, La Nina events occur whenever the Walker Circulation pattern is stronger than normal. The data shows that there is an 11-year cycle in the long-term strength of La Nina events that must be related to the 11-year solar sunspot cycle.
Hence, I would contend that while the energy transfers through the climate system require that the El Nino and La Nina phenomenon work together, the occurrence of an El Nino event does not necessarily lead to the onset of a following La Nina event.
Thus, It is probably more accurate to say that the 11-year cycle in the long-term strength of La Nina events is being effectively disrupted/moderated by the occurrence of El Nino events, roughly once every 4.5 years.
Hi Ian, you wrote above:
“Historically, there are many cases where moderate to strong El Nino events have not immediately (~ 1-2 years) been followed by La Nina events e.g. the 1982/83 and 1991/92 El Ninos.”
Not sure if this helps, but the atmospheric temperatures in both 1982+ and 1991+ were tempered (reduced) by century-scale volcanoes El Chichon and Mt. Pinatubo.
https://www.facebook.com/photo.php?fbid=1618235531587336&set=a.1012901982120697.1073741826.100002027142240&type=3&theater
The blue line in the plot (UAH LT global atmospheric temperature calculated wwithout Sato) is a direct function of NINO34 Sea Surface Temperature (SST).
The yellow line (UAH LT global atmospheric temperature calculated with Sato) is a direct function of NINO34 SST and the Sato volcanic air opacity index.
The red Line is the actual UAH LT global atmospheric temperature.
Regards, Allan
Absolutely meaningless.
The Paper I mean…not any of the comments!
A year ago, April 2017, I wrote about this at:
https://judithcurry.com/2017/04/30/nature-unbound-iii-holocene-climate-variability-part-a/
“ENSO activity was essentially absent during most of the HCO and first becomes statistically significant around 7,000 yr BP, increasing considerably after 5,600 yr BP, and displaying many very strong peaks of activity during the Neoglacial period.
From a thermodynamic point of view high ENSO activity transfers great amounts of heat from the ocean sub-surface to the atmosphere, and afterwards a great part of that heat is radiated to space. This constitutes a cooling event from a whole Earth climate system perspective, even if it appears as warming from a lower atmosphere perspective. It is proposed that high ENSO activity is made possible by a high equator-to-pole temperature gradient. During the HCO [Holocene Climatic Optimum] the temperature gradient was kept low by high polar insolation due to high obliquity. After 7,000 yr BP the decrease in polar insolation and the increase in tropical insolation favored a progressive increase in the gradient, especially during prolonged periods without significant cooling, i.e. immediately preceding a Bond event. The profound cooling from a Bond event would eliminate or greatly reduce ENSO activity by quenching the thermal energy required for an El Niño event. If correct, high ENSO activity would be a sign of a cooling planet.”
Most people don’t understand ENSO properly. El Niño is a short-circuit in the ocean driven latitudinal transport of energy in the tropics. This transport is driven by the Equator-to-Pole temperature gradient. As the gradient increases, the need to transport heat increases, the transport system can’t cope and an El Niño ensues. Part of the excess heat is directed to the atmosphere taking a more direct route out of the planet.
With global warming, the gradient has decreased, and so the frequency of El Niño events decreases.
El Niño is exactly the opposite most people think. It cools the planet, and it is a sign of a cooling planet. It just temporary warms the atmosphere as the heat passes through it.
What I mean is that the article is not controversial to established knowledge. Scientists already knew all this. All models are wrong, but some are useful. The paper indicates progress towards understanding the causes behind El Niño, since what the evidence showed, can to some extent be modeled. The model supports attribution to changes in insolation during the Holocene. The Sun is by far the main cause of climate change, as anybody could imagine. Over centennial to millennial scales ENSO changes are not climate neutral. They are driven by climate change as a result of changes in solar insolation from orbital changes and from solar activity changes.
Javier,
I wholeheartedly concur with your posted comments, particularly the remarks about how El Nino events are a (short-circuit) cooling mechanism for the planet.
However, I am a bit wary of the proxy that you have used to indicate the frequency of ENSO events.
If you look carefully at your graph, you have two major cooling events [among the four strongest] centered at 450 A.D. and 1200 A.D. The first is at the transition between the end of the Roman Empire and the Dark-Ages and the second is right at the peak of the Medieval Warm Period.
I can understand that at the peak of the Medieval Warm Period (circa. 1200 A.D.) the polar-equator temperature gradient was likely to be large and hence the rate of El Nino events should have been high.
However, I do not think that the world was particularly warm around 450 A.D.
It is important to validate a proxy if it is to be believed. Is there any evidence that the proxy that is used here for El Nino frequency has been validated using modern data?
Javier,
Sorry, I got it the wrong way around. one paragraph should have read
I can’t understand that at the peak of the Medieval Warm Period (circa. 1200 A.D.) the polar-equator temperature gradient was likely to be small and hence the rate of El Nino events should have been low.
However, I do not think that the world was particularly warm around 450 A.D. and so you might expect a higher polar-to-equatorial temperature gradient and hence a higher number of El Nino events.
Soon-Il An has been publishing papers on chaotic dynamics of ENSO against a background of alternating “ground states” in the Pacific, for decades.
There might in fact be some sort of connection between ENSO and ice ages:
the studies by Stott and Koutavas suggest that shifts between warm and cool global average temperatures look, from the perspective of the tropical Pacific, like super El Niños. So too do the swings from shorter-term warming and cooling spells, called interstadials and stadials, that punctuated the last ice age.
It’s not clear, say Stott and colleagues, whether these changes imply that the climate was persistently in an El Niño-like phase during ice ages, or whether such phases came and went every few years, as they do at present, but more frequently and more intensely.
http://www.nature.com/news/2002/020712/full/news020708-19.html
Evidence of droughts and unusually wet weather, chemically etched into ancient reefs, show changes every three to seven years [124kya, during the previous interglacial], a pattern that Schrag finds “remarkably similar” to those of El Niños from 1856 to 1976. After that, a sudden change occurred. Since 1976, the pattern looks completely different, with El Niño events appearing faster and stronger.
https://news.harvard.edu/gazette/story/1999/08/el-nino-found-to-be-124000-years-old/
The authors* [Meyerson, Mayewski, et al. (Annals of Glaciology 35: 430-436.] found that a shift toward cooler conditions during the Little Ice Age was concurrent with an increase in the frequency of El Niño events. This is contrary to what is generally predicted by climate models, where cooling leads to less El Niño activity and warming leads to more.
The findings were harmonious with El Niño history in both South America and the Nile region, which depict “increased El Niño activity during the period of the Little Ice Age and decreased El Niño activity during the Medieval Warm Period.
https://www.iceagenow.info/el-nino-activity-correlates-with-ice-ages/
In this study we isolate a part of the climate system, the tropical Pacific, and test its sensitivity to changes in solar forcing associated with changes in the Earth’s orbital parameters. We use a simplified coupled ocean-atmosphere model that is run for the past 150,000 years and forced with Milankovitch changes in the solar insolation. This system responds primarily to the precessional cycle in solar forcing and is capable of generating a mean response to the changes in the seasonal distribution of solar radiation even while the annual mean insolation is roughly constant. The mean response to the precessional forcing is due to an interaction between an altered seasonal cycle and the El Nifio/Southern Oscillation (ENSO). Changes in the ENSO behavior result in a mean tropical climate change. The hypothesis is advanced that such a change in the tropical climate can generate a globally synchronous climate response to Milankovitch forcing.
http://muenchow.cms.udel.edu/html/classes/seminar/abstracts/ElNinoOrbital_Zach.pdf