Guest Post by Willis Eschenbach
On another thread, a poster got me thinking about the common practice of using the El Nino 3.4 Index to remove some of the variability from the historical global average surface temperature record. The theory, as I have heard it propounded, is that the temperature of the Earth is “signal”, whereas the El Nino cycles are natural swings and as such are just “noise”. So if you remove the El Nino swings from the temperature, the theory goes, then we can see more of the underlying temperature signal by removing the noise.
Figure 1. Various “Nino regions” used in the study of the El Nino / La Nina phenomenon. Each area has its own index, with one of the most commonly used being the Nino 3.4 Index. SOURCE. See also the NOAA page
The more I thought about the practice of subtracting the Nino 3.4 variations from the global average temperature anomalies, the more questions came up for me. I don’t have the answers, hence this post. The first question that came up is, how do we decide that the Nino 3.4 Index represents noise instead of signal?
The Nino 3.4 region covers about 2.4% of the planet’s surface, a bit bigger than the USA. So … why isn’t the temperature of the USA “noise”? Or perhaps, is the temperature of the US “noise” but no one ever checked? And how would you check? What mathematical procedure would allow us to discriminate? What test would we use to say well, Nino 3.4 is noise so we can safely subtract its effects from the global temperature signal, but, for example Nino 1+2 is not noise, it’s part of the signal?
My next question about the situation revolves around the fact that the Nino 3.4 Index is merely a linear transform of the sea surface temperature of the Nino 3.4 area. So what we are doing is taking a linear transformation of the surface temperature anomaly in one part of the world, and subtracting it from the global average surface temperature anomaly.
As a result the question is, is this a legitimate operation? Subtracting a linear transform of something from the whole of which it is a part? Like, say, taking the average temperature variations in the whole US including Texas, but then subtracting out some linear transform of the temperature variation in Texas? What is the meaning of that procedure, subtracting something from itself? And if we are going to subtract a transform of say the Nino 3.4 temperature from the global average, should we include the Nino 3.4 temperature to begin with when we calculate the global average, or not?
Next question is, is this a legitimate operation in a system with a thermostat? Like for example, taking the variations in my body temperature, but subtracting out some linear transform of the temperature variations in my foot? What does that procedure give us, what does the result mean?
Next question. If we’re going to remove the transform of the El Nino Index from the global average temperature record, then should we remove the other indices as well? Should we remove the AMO (Atlantic Multidecadal Oscillation) Index? The PDO (Pacific Decadal Oscillation) Index? The Madden-Julian Oscillation Index? Some combination of them? All of them?
Final question. From my perspective, the El Nino/La Nina oscillation actively regulates heat loss, and thus is part of the planetary temperature regulation system. It regulates the heat loss by way of both the ocean and the atmosphere. Let me give a functional explanation of how it works. The explanation is slightly but not significantly simplified.
During La Nina conditions, in the upper part of Figure 2 below, the warm blanket of water normally covering the Pacific has been blown to the west by the strong eastern trade winds. From there, that mass of warm Pacific surface water splits and moves north and south along the coasts of Asia and Australia towards the Poles. The mass of water is radiating and losing heat as it travels. Functionally, the El Nino/La Nina alteration serves as a huge, slow-cycling, thermally regulated Pacific-wide pump. The La Nina pump stroke moves warm Pacific surface water poleward to lose its heat through conduction, radiation, and evaporation.
Figure 2. La Nina and El Nino conditions. North and South America are the brown areas in the upper right. Australia is at the lower left. Black arrows in the atmosphere show the direction of atmospheric circulation. White arrows show surface ocean currents SOURCE: NOAA El Nino Theme Page
In addition to moving warm Pacific water poleward, the removal of the warm Pacific tropical surface waters exposes the atmosphere to huge amounts of cooler sub-surface Pacific water. This lowers the air temperature over that whole area of the tropical Pacific. Soon, however, the surface of the Pacific starts to warm again. One effect of this is that it slows down the eastern trade winds. As a result of reduced winds and reduced clouds, the warming of the surface of the Pacific continues. In addition, some of the warm surface water in the Western Pacific moves back out east. Soon, with the sun beating down on an ocean with reduced clouds, it warms up all across the Eastern Pacific. This leads to neutral conditions, which can last a while.
However, if the tropical Pacific surface temperature warms enough, then El Nino conditions develop. After the El Nino conditions come into being, at some point as the surface of the Pacific continues to warm, and the El Nino thunderstorms drive the surface air upwards, the eastern trade winds start to strengthen. Soon the eastern trade winds start pushing the warm tropical surface waters and their associated thunderstorms and clouds to the west across the Pacific and eventually poleward again. This is the power stroke of the pump, when the trade winds strip the warm surface waters off and push them westwards. In this process, the full La Nina conditions come into existence. Finally, the La Nina conditions eventually peter out to a neutral condition once again.
Note that this system is triggered by temperature. If the temperature doesn’t build up across the surface of the eastern Pacific for some reason, then things stay neutral, neither El Nino or La Nina. In that case, the El Nino doesn’t form, and so the eastern trade winds don’t build up to pump the warm water across the Pacific and towards the poles.
But when the surface waters of the Pacific do heat up beyond a certain point, El Nino conditions arise, the eastern trade winds strengthen and pump the warm tropical surface water, first across the Pacific and then to the poles. It also exposes the atmosphere to a large area of cooler subsurface water.
Note the effect of this amazing temperature regulating heat pump. It functions to prevent any long-term buildup of heat in the waters of the surface Pacific. If the water in the surface of the Pacific stays cooler, the heat pump doesn’t kick in. But as soon as a certain amount of heat builds up in the surface Pacific waters, the El Nino/La Nina alteration occurs, pumping the surface water west to be flushed out toward the poles. The layer of warm surface water that was blown west is then replaced by cooler water from the subsurface, cooling the entire tropical Pacific.
This mechanism, this El Nino/La Nina pump skimming off the hot Pacific water and pumping it to the poles, prevents long-term Pacific heat buildup and thus actively keeps the planet from both overheating and excessive cooling. It is one of the many interacting thermoregulating mechanisms that keep the earth from either overheating or becoming too cool.
So … this brings up the final question regarding the theme of this post.
Since the variations in the Nino 3.4 index are indicative of the functioning of one of the Earth’s major thermoregulating mechanisms, namely the giant El Nino/La Nina pump that magically materializes to move warm tropical Pacific water to the poles whenever the planet gets too hot and sweaty … then under what possible construction could the Nino 3.4 Index variations be called “noise”?
Like I said … lots of questions, I don’t have the answers, all courteous contributions welcomed.
Regards to all,
w.
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On a slightly tangential topic, why do we use a “global temperature” parameter that is a compound of sea surface temperature ( or about 1 metre below the surface or whatever) and air temperature ( at about 1 to 2 metres above the surface)? In determining a representative temperature of say San Francisco would you mix air temperatures over land with sea temperatures from the bay in the same way? What would the number you obtained mean? Would it be unreasonably low due to the sea temperatures or would it be unreasonably high and volatile due to the land air temperatures?
So could a mechanism that disrupts the cycle of enso be the cause of ice ages? Not sure what it might be just yet.
Isn’t this topic yet another indication that for purposes of making climate-related predictions, the signal/noise paradigm of temperature signal versus weather noise is a completely flaky proposition — all of it, the whole signal/noise paradigm.
Sounds like a logical robust thought process. The first question I would ask is what difference does it make if you put it back in? Do you have a graph summarising the overall change?
You would need to know exactly how much of the temperature was the result of Enso in order to subtract it. I’m pretty sure we don’t know what that is.
Willis, if any long-term 60-year cycles were included, you would have this:
1 warming period in 19th Century – recovery from global LIA, not (by common consent) CO2.
1 period of flatline.
1 warming period in 1st half of 20th Century – not (by common consent) CO2.
1 period of flatline.
1 warming period in 2nd half of 20th Century – cause caustically debated!
1 period flatline (2000 – 2030).
….and so on.
That wouldn’t fit the CO2-is-everything warmist script at all.
The problem is why to alter the data at the first place?
We see a problem whit temperatures because they tweak the data so they get the warming they want. Now they be leaf there is warming because the data says so but they alter the data 3 times before the final numbers get out. So how mutts cooler is it now? 0,5 or 1 or even 2 or 3 degrees? I think we cane say easy that is 1,5 degrees cooler then they say.
But why alter the data? A thermometer saying its 25 says its 25! That means its 25 not 28. If you take boiling water and put a thermometer in it and it reads 100 degrees Celsius then you can be verily sure thats 100 degrees, way would someone say that its 105 degrees or 95?
If you want to be sure of what you do, you must look at the thermometer and wright whats stand there no more no less. Whit the oceans the same, read what the thermometer says and wright it down no more no less.
All the Nino, Nina, Pdo, PDA’s and what more are part of the climate and must be taken just lake that.
Every other thing done to the data like AGWers like to do is Freud and far from being scientific.
Willis:
A fine post. Thankyou.
As to your major question;
No, it is not sensible to remove ENSO effects from the temperature record because ENSO is a natural part of the global climate at any time.
1.
When the 1998 ENSO peak in b.onal temperature occurred the warmunists proclaimed this was the start of what we could expect: more frequent and hotter ENSO effects which raise global temperature.
2.
Now, when global temperature rise has stalled, warmunists say ENSO should be subtracted from global temperature rise.
Point 1 was a falsehood.
ENSO is an emergent property of the climate stystem which GCMs fail to emulate, so there is no way to determine if more or fewer ENSO events will occur. However, as you point out, heat triggers ENSO events which redistribute the heat so it gets ‘dumped’ to space and, therefore, the effect of more frequent ENSO would probably reduce the rate of any global temperature rise. Indeed, since the 1998 ENSO peak the global temperature has varied such that there has been zero trend in the temperature.
Point 2 is an excuse for the stall in global temperature rise over the most recent 15+ years.
Richard
The ocean not only has this great heat pump, it is a gigantic heat sink, requiring 1154 times the energy to change one degree in temperature as the atmosphere. Since the El Nino cycle influences atmospheric temperature, the is obviously some nearby atmosphere/water temperature delta at which almost all additional atmospheric heat effectively goes straight to the ocean rather than atmospheric temperature.
Willis, this is an important question and I believe the answer is as you expect – it isn’t noise and should not be removed, at least if you are looking for the Global temp signal. Regarding the mechanism of the ENSO pump, I think currents should be included in defining the system:
http://www.google.com.do/imgres?imgurl=http://www.probertencyclopaedia.com/photolib/maps/Map%2520of%2520Pacific%2520Ocean%2520%28Currents%29%25201966.jpg&imgrefurl=http://www.probertencyclopaedia.com/photolib/maps/Map%2520of%2520Pacific%2520Ocean%2520%28Currents%29%25201966.htm&h=871&w=1000&sz=123&tbnid=Y9X3sNuCx8CJJM:&tbnh=90&tbnw=103&zoom=1&usg=__j8MvOs3LzBIhsa0qCjou8Kt37EY=&docid=p_sNn7Mg-vjivM&sa=X&ei=wBH4UJudOIyi8QTrpYHICw&ved=0CDQQ9QEwAA&dur=51
The California current and the Peruvian current go (south and north respectively) toward the equator and then swing westward in the region we are discussing. This must also be an important mover of the surface water’s westward. Moreover, they may also be warm(ing) water gathering mechanisms to concentrate warm water in the equatorial band. It is also known that geothermal energy particularly warms the pacific waters around its rim (the ring of fire) – perhaps not a large factor but, it, too, would be gathered and moved to the equatorial zone by the currents. This may even be why we don’t have an “ENSO” in the equatorial Atlantic (highly speculative, I’ll admit).
Willis, I suspect the reason to take it out of the record was to prove that the remaining warming had to be from anthropogenic causes. That in turn morphed into the mankind is bad and causing all this …. blah. 1997-1998 was the back breaker. ENOS could no longer be denied. Coupling that ENSO event we recognized the existence of the Pacific Decadal Oscillation. Suddenly the A/CO2 theory could no longer be fully supported as the major cause. More natural events and their causes make A/CO2 less viable. Accordingly we get the shift in terminology (add you growing list here.)
So it is my belief that removing the ENSO and all natural signals is just noise to prop up the A/CO2 theory.
Succinct post Willis.
However, what causes the 30 year positive and negative PDO cycles which have more El Ninos or La Ninas respectively? We don’t see 30 year cycles in the source of the energy for this heat pump, the Sun.
Alan
If El Nino is arbitrarily defined then it is a qualitative, not quantitative, description. I have not yet heard of of the S.I. Units of ENSO, AMO, etc.
Willis, did you get Bob’s permission to post about ENSO? I thought he owned the rights.
Nothing is actually ‘noise’, except perhaps measurement uncertainty.
Everything is a signal of some sort, whether it indicates changes in ENSO, PDO, AMO, or whatever else.
And one major problem with some papers is the assumption that they are able to identify all the ‘natural’ variations to be removed from the data to reveal the supposed anthropogenic component.
Even if the data adjustments were valid (eg- Rahmstorf and Foster) , it is not reasonable to deem the remainder to be all due to CO2 and supposed feedbacks, since we have no way of knowing what other unknown factors might be involved in that remainder.
This especially when there is reason to suspect (from the work of Svensmark, Kirkby, and others) that there is a solar and cosmic ray contributor to global temperature changes that has not been considered at all in the current climate models.
This post nicely elucidates something that I noticed as well. Despite the attempts of the IPCC to convince us otherwise, there is no formal structure to the overarching AGW inquiry. There is no logic tree being formally resolved, so AGW proponents are free to write whatever they want. They are a herd of cats. Climate science is hopelessly mired in what would be merely the first phase of an engineering risk analysis, “is the thermostat broken or overwhelmed?.” Stripping out El Nino effects is an interesting way to look at how the thermostat works, but does absolutely nothing to resolve the questions facing AGW.
With regards –
Bloke down the pub says:
January 17, 2013 at 7:00 am
So could a mechanism that disrupts the cycle of enso be the cause of ice ages? Not sure what it might be just yet.
It would be reasonable to assume that the “mechanism” that triggers the ice ages and disrupts this cycle will be “off world.” That is, a Solar cycle – sort of like what we are seeing now regards solar activitiy.
Another very good post, clear and concise. Thanks Willis!
To separate the noise from an underlying signal you must know a lot about the signal. If you don’t, the results are bound to deceive you. Global Circulation Models can not be used to learn about the temperature signal, only data serves that purpose.
Perhaps the global temperature record is the noise and the El Nino 3.4 Index is the signal?
Why not? Isn’t the global temperature record extremely noisy due to factors such as changing distribution of thermometers, changes to surrounding land areas due to agriculture and urbanization, as well as changes in the ocean due to flora and fauna due to industrialized fishing?
Perhaps the El Nino 3.4 Index is the true signal?
When Revkin featured Skeptical Science’s propaganda graph of global surface temperature with “noise” removed [ http://dotearth.blogs.nytimes.com/2013/01/09/shift-in-british-climate-analysis-blunts-governments-short-term-warming-forecast/ ], I called the exercise the equivalent of the stage magician’s trick of ‘forcing a card’.
I like the questions….the idea of removing part of the actual temperature record itself as ‘noise’ is, I believe, entirely fallacious.
Dear Willis,
With all due respect, your claim that ENSO SSTs “modulate” the trade winds/AAM state is incorrect. There’s a reason they “start to warm” again. You’ll find that variation in the annular modes/the associated mid latitude stress fields/standing gyres precede variations in the SOI and ONI/MEI by several months. This activity correlates extremely well to the rocking phase of the QBO and variations in solar activity, specifically geomagnetic activity, which correlates to O^3 levels hence Rossby amplitude.
I just wrote a detailed comment..was asked to log in, then poof, all that work..gone. I’m not sure I want to redo it all.
Alan Millar says:
January 17, 2013 at 7:33 am
However, what causes the 30 year positive and negative PDO cycles which have more El Ninos or La Ninas respectively? We don’t see 30 year cycles in the source of the energy for this heat pump, the Sun.
=====
First harmonic between Jupiter and Saturn orbits is 60 years.
We have no data on how natural climate change has manifested. Was it even all over the world? A change in frequency and strength of ENSO? So much of climate science can be dismissed as “stupid” number tricks”, including removing ENSO.
It is pretty standard practice in geophysical data analysis to remove sources of variation that are well understood, in order to better quantify the “anomalies” that are of interest. One example would be the standard practice of backing out effects of elevation and latitude from raw gravity measurements. There are two caveats, though. You shouldn’t be backing anything out unless it is very well quantified, and you have to be absolutely consistent. No fair talking about how hot 1998 was and then suggesting ENSO should be backed out of the temperature record.