La Nina – The Underappreciated Portion Of ENSO
Guest post by Bob Tisdale
Perform a Google Scholar search for documents including “El Nino” in quotes and there will be more than 200,000 results. On the other hand, “La Nina” will only raise 26,000+. Granted, the formal name of the coupled ocean-atmosphere phenomenon in the tropical Pacific is “El Nino-Southern Oscillation”, but that in quotes only returns 28,000+ results. So it appears that El Nino events do get much more “press” from the scientific community than La Nina events.
Figure 1 is a time-series graph of NINO3.4 SST anomalies from January 1979 to January 2010. El Nino events are a warming of the central and eastern tropical Pacific so they are displayed as a Positive SST anomaly, where La Nina events are a Negative. Visually, is the eye drawn to the upward spikes more than it is to the downward troughs? El Nino events are viewed as being larger in magnitude than La Nina events. NINO3.4 SST anomalies peaked at approximately 2.8 deg C during the Super El Nino events of 1982/83 and 1997/98, while the La Nina events that followed them failed to reach -2 deg C. But the La Nina events of 1988/89 and 2007/08 were stronger than the El Nino events that preceded them. (Refer to the note about base years at the end of this post.)
http://i48.tinypic.com/dpikxz.png
Figure 1
El Nino events release heat from the tropical Pacific, and through ocean currents and changes in atmospheric circulation, they raise surface temperatures outside of the tropical Pacific. These upward spikes in global temperatures, Figure 2, call attention to El Nino events during periods when global temperatures are rising. During La Nina events, the tropical Pacific releases less heat than normal, and global temperatures decline, which doesn’t have the same visual impact.
http://i45.tinypic.com/28wjsdy.png
Figure 2
La Nina events are a vital portion of the El Nino-Southern Oscillation coupled ocean-atmosphere process. La Nina events recharge the heat released from the tropical Pacific during the El Nino. Figure 3 is a graph of Tropical Pacific Ocean Heat Content compared to scaled NINO3.4 SST anomalies. Note that most La Nina events do not fully recharge the heat released by the El Nino events. From 1976 to 1994, tropical Pacific Ocean Heat Content dropped almost continuously, with occasional major dips and rebounds as an El Nino discharged heat and the subsequent La Nina partially recharged it. Then, the 1995/96 La Nina event, one that was not particularly strong, replaced all of the heat that had been released (plus some) over that 18-year stretch.
http://i46.tinypic.com/2vja1z5.png
Figure 3
THE 1995/96 LA NINA PROVIDED THE FUEL FOR THE NEXT EL NINO
During a La Nina event, tropical Pacific trade winds rise above normal levels. The increase in trade winds reduces cloud cover. Reduced cloud cover allows more Downward Shortwave Radiation (visible light) to warm the tropical Pacific. These coupled ocean-atmosphere processes associated with La Nina events were discussed in the post More Detail On The Multiyear Aftereffects Of ENSO – Part 2 – La Nina Events Recharge The Heat Released By El Nino Events AND…During Major Traditional ENSO Events, Warm Water Is Redistributed Via Ocean Currents”.
As noted above, the 1995/96 La Nina was not a strong event, yet it recharged all of the ocean heat that had been released in almost two decades of El Nino events. In “Genesis and Evolution of the 1997-98 El Niño” [ Science 12 February 1999: Vol. 283. no. 5404, pp. 950 – 954, DOI:10.1126/science.283.5404.950], Michael McPhaden explains, “For at least a year before the onset of the 1997–98 El Niño, there was a buildup of heat content in the western equatorial Pacific due to stronger than normal trade winds associated with a weak La Niña in 1995–96.” Link to Science abstract:
http://www.sciencemag.org/cgi/content/abstract/283/5404/950
Link to NOAA copy of McPhaden (1999):
http://www.pmel.noaa.gov/pubs/outstand/mcph2029/text.shtml
So there was a short-term recharge of tropical Pacific Ocean Heat Content in 1995/96, which is very evident in Figure 3. And this short-term buildup of heat content provided the fuel for the 1997/98 El Nino. Contrary to the beliefs of anthropogenic warming proponents the 1997/98 El Nino was NOT fueled by a long-term accumulation of heat from manmade greenhouse gases.
AND THAT 1997/98 EL NINO WAS CALLED THE EL NINO OF THE CENTURY
The 1997/98 El Nino was strong enough to temporarily raise Global Lower Troposphere Temperature anomalies ~0.7 deg C, as illustrated in Figure 4. Note: The period of 1995 to present was used in the following graphs because there have been no explosive volcanic eruptions since 1995 to add unwanted noise to the data.
http://i47.tinypic.com/21nnu4z.png
Figure 4
And referring to Figure 5, Lower Troposphere Temperature anomalies of the Mid-To-High Latitudes of the Northern Hemisphere rose, but remained at elevated levels that varied well above the value in late 1996. This upward step (and a similar but smaller one caused by the 1986/87/88 El Nino) was discussed in the post “RSS MSU TLT Time-Latitude Plots…Show Climate Responses That Cannot Be Easily Illustrated With Time-Series Graphs Alone”.
http://i48.tinypic.com/33p6nbn.png
Figure 5
Sea Surface Temperature anomalies for the Mid-To-High Latitudes of the Northern Hemisphere also rose and remained at an elevated level. Refer to Figure 6, which compares that dataset to scaled NINO3.4 SST anomalies. The latitudes used for the SST anomalies in this illustration are 20N-65N, which are latitudes that have little impact from polar ice. This upward step in the Sea Surface Temperature anomalies for the Mid-To-High Latitudes of the Northern Hemisphere will be discussed in a future post. I have, however, discussed the impacts of El Nino events on the North Atlantic in the post There Are Also El Nino-Induced Step Changes In The North Atlantic. And the North Atlantic is also impacted by the Atlantic Multidecadal Oscillation, but that appears to have peaked in 2005.
http://i46.tinypic.com/2ylpix3.png
Figure 6
And for those wondering how well the SST and TLT anomalies for the Mid-To-High Latitudes of the Northern Hemisphere correlate, I’ve prepared Figure 7. The SST anomaly data were scaled by a factor of 1.8. There are divergences from year to year, but keep in mind that the coverage areas are very different; the TLT anomalies also include data over continental land masses. One thing is certain; the 1997/98 El Nino caused upward steps in both datasets.
http://i49.tinypic.com/2uo2o8y.png
Figure 7
And there are the impacts of the 1997/98 El Nino on the East Indian and West Pacific Oceans (60S-65N, 80E-180), which I first discussed in a series of posts more than a year ago. The 1997/98 El Nino shifted Sea Surface Temperature anomalies upward in this area of the global oceans, too. Refer to Figure 8. The cause of this was discussed in the posts Can El Nino Events Explain All of the Global Warming Since 1976? – Part 1 and Can El Nino Events Explain All of the Global Warming Since 1976? – Part 2.
http://i48.tinypic.com/2qamu88.png
Figure 8
Basically, the warm water that was built up during the 1995/96 La Nina collected below the surface of an area in the western tropical Pacific known as the Western Pacific Warm Pool (to depths of 300 meters). During the 1997/98 El Nino, the warm water contained in the Western Pacific Warm Pool sloshed east and spread across the surface of the central and eastern tropical Pacific. The warmer-than-normal waters raised Sea Surface Temperatures and changed atmospheric circulation. Then, as the La Nina of 1998/99/00/01 progressed, the trade winds, Pacific Equatorial Currents, and a phenomenon known as a Rossby wave returned the remaining surface and subsurface warm water to the western Pacific. Some of the warm water returned to the Pacific Warm Pool, but a major portion of it remained on the surface and was redistributed by ocean currents to western North and South Pacific, and a portion of the warm water migrated to the Eastern Indian Ocean.
BLAME THE 1995/96 LA NINA FOR THE RECORD TEMPERATURES DURING THE 2000s AND IN 2010
So, if you’re wondering why the present moderate El Nino event of 2009/10 is raising global temperatures to record levels, you have to go back in time. The 1995/96 La Nina provided the build-up of warm waters that was then discharged by the 1997/98 El Nino and redistributed by the 1998/99/00/01 La Nina. The end results were upward steps in SST anomalies and TLT anomalies for major portions of the globe.
One of the methods anthropogenic global warming advocates (scientists and bloggers) use to illustrate the assumed effects of greenhouse gases on global temperatures is to illustrate the divergence between the linear trends of global temperatures and a scaled ENSO index such as NINO3.4 SST anomalies. Refer to Figures 9 and 10. But the upward steps illustrated in Figure 5 and 6 bias global temperature data upwards.
http://i46.tinypic.com/2vsl2mr.png
Figure 9
##############
http://i50.tinypic.com/2d7j0ux.png
Figure 10
And the biases created by those step changes in the SST and TLT anomalies of the Mid-To-High Latitudes of Northern Hemisphere are responsible for much of the differences between NINO3.4 SST anomalies and global temperature anomalies. We can illustrate this looking at the data for the rest of the world; that is, by comparing the linear trend of NINO3.4 SST anomalies with the linear trends the TLT and SST anomalies for the tropics and the Mid-To-High Latitudes of the Southern Hemisphere. Refer to Figures 11 and 12. As shown, the linear trends of the NINO3.4 SST anomalies are slightly negative, but the linear trends for the SST and TLT anomalies of the tropics and Mid-To-High Latitudes of the Southern Hemisphere are relatively flat–much flatter than the global datasets.
http://i50.tinypic.com/vsn97q.png
Figure 11
#####################
http://i49.tinypic.com/11mcj7p.png
Figure 12
That would mean the ENSO-induced step increases in SST and TLT anomalies of the Mid-To-High Latitudes of the Northern Hemisphere caused the vast majority of the positive linear trends for the global SST and TLT anomaly datasets. See Figures 13 and 14, which show the strengths of the positive trends for those areas of the globe.
http://i47.tinypic.com/i4okg2.png
Figure 13
#####################
http://i50.tinypic.com/35347qh.png
Figure 14
Figures 15 and 16 compare the SST and TLT anomalies for the Mid-To-High Latitudes of the Northern Hemisphere to the Global data and to the SST and TLT anomalies for the Mid-To-High Latitudes of the Southern Hemisphere. It should now be clear that the majority of the rises in Global SST and TLT anomalies since 1995 were caused by the 1997/98 El Nino-induced upward steps in the SST and TLT anomalies for the Mid-To-High Latitudes of the Northern Hemisphere.
http://i50.tinypic.com/33p64k1.png
Figure 15
#####################
http://i47.tinypic.com/1zywv8k.png
Figure 16
In short, the effects of the La Nina- and El Nino-induced step changes in the SST and TLT anomalies of Mid-To-High Latitudes of the Northern Hemisphere are mistaken for, and misrepresented as proof of, anthropogenic global warming.
A BRIEF LOOK AT AN EARLIER LA NINA EVENT
The 1972/73 El Nino was a strong ENSO event. NINO3.4 SST anomalies, referring to Figure 17, peaked above 2 deg C. There were only two El Nino events stronger than the 1972/73 El Nino in the second half of the 20th Century, and they were the two Super El Nino events of 1982/83 and 1997/98.
http://i46.tinypic.com/29krqd2.png
Figure 17
But the 1972/73 El Nino shares another superlative with the 1997/98 El Nino. Both El Nino events were followed by La Nina events that lasted through not one ENSO season, not two ENSO seasons—they lasted through three consecutive ENSO seasons. The La Nina event of 1998/99/00/01 recharged the heat content released by the 1997/98 El Nino and returned the tropical Pacific Ocean Heat Content to the new higher levels established during the 1995/96 La Nina. Refer to Figure 18. The La Nina event of 1973/74/75/76 recharged the heat released from the Tropical Pacific by El Nino events during the decade of the early 1960s to the early 1970s. And it also added to the Tropical Pacific Ocean Heat Content.
http://i46.tinypic.com/2vja1z5.jpg
Figure 18
The Pacific Climate Shift of 1976/77 is a much-studied phenomenon. Trenberth et al (2002) discussed the differences in the evolution of El Nino events before and after the shift, and Trenberth et al (2002) referenced other papers that discussed effects of the Pacific Climate Shift on ENSO. Link to Trenberth et al (2002):
http://www.cgd.ucar.edu/cas/papers/2000JD000298.pdf
El Nino events became stronger after the Pacific Climate Shift. The frequency of El Nino events and El Nino Modoki increased. As noted in an early post, The 1976 Pacific Climate Shift, there were notable shifts in the SST anomalies and linear trends of Pacific Ocean basin subsets.
But I have yet to find a paper that attributes the Pacific Climate Shift of 1976/77 to the La Nina event of 1973/74/75/76 or one that even suggests that the 3-year-long La Nina played a role. Yet through known coupled ocean-atmosphere processes, the 1973/74/75/76 La Nina increased the warm water available for the additional El Nino events after 1976 and for the significant El Nino events of 1982/83 and 1986/87/88.
The explosive volcanic eruption of El Chichon may have counteracted the Super El Nino of 1982/83, but the 1986/87/88 El Nino was strong enough to cause upward shifts in the SST and TLT anomalies of the Mid-To-High Latitudes of the Northern Hemisphere, and the SST anomalies of the East Indian and West Pacific Oceans, similar to the shifts caused by the 1997/98 El Nino illustrated in this post.
A NOTE ABOUT BASE YEARS
Note: The relative strengths of El Nino versus La Nina events discussed early in this post would of course depend on the base years chosen for anomalies. And as illustrated in Figure 17 there is a minor difference depending on whether the base years of 1950 to 1979 or 1979 to 2000 are used. The significance of the difference would depend on how the data is being used. Example: A scaled running total of NINO3.4 SST anomalies will reproduce the basic global temperature anomaly curve as illustrated in Reproducing Global Temperature Anomalies With Natural Forcings if the base years are 1950 to 1979. If the base years of 1979 to 2000 are used, the result will not be similar to the global temperature curve.
http://i47.tinypic.com/2wlrkf4.png
Figure 19
CLOSING COMMENT
The La Nina event of 1973/74/75/76 provided the tropical Pacific Ocean Heat Content necessary for the increase in strength and frequency of El Nino events from 1976 to 1995. The 1995/96 La Nina furnished the Ocean Heat Content that served as fuel for the 1997/98 El Nino. And the 1998/99/00/01 La Nina recharged the tropical Pacific Ocean Heat Content after the 1997/98 El Nino, returning it to the new higher level established by the La Nina of 1995/96.
It would appear that La Nina events do all of the work, while El Nino events get all the glory—and the research.
SOURCE
All data for this post is available through the KNMI Climate Explorer:
http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere
Richard M (09:21:09) :
I have suggested a Lunar connection. Eclipses give extra tidal forces and when hitting low latitudes mass will get pulled towards the equator. This could change currents (atmos and ocean) either directly or via changing earth’s rotation. http://virakkraft.com/uah-rss-moon.png
It seems that endless days and nights of CTD deployments,busted fingers,burned hands, 200 plus days a year seatime, busted marriages, the loss of good shipmates, melanoma, etc. provided some data afterall.
Heres to the crews of the “Oceo” and the “Disco”.
Tradewind days shipmate.
Thanks Bob
Bob,
I wish you would apply your attention to what drives or triggers ENSO and/or PDO because that is where climate truth resides.
The NOAA link is not helpful in that respect nor was the reply to stephen richards.
The fact is that there appears to be an ocean driven cycle from MWP to LIA to the Modern Warm Period and we need to bridge the gap from your ENSO work to that longer term cyclical phenomenon.
Unless we can do that then regrettably all your work is of little value in terms of the background climate changes upon which ENSO is superimposed.
ENSO itself is of little value if it can only deal with shorter term climate variability.
I’m trying to help you here.
Rotational energy.
Physicist are about to hate my guts but…
You will not find this in any book as it was experimentation and theory and getting results.
Our Planets and suns rotational energy is what has been infused already into the planet and sun by density changes. The slowdown is the slow release of this energy until it is all used up. The moons small density will have an effect on the surface of the planet as water is denser than land and has elasticity to it. Slowdown the planet? Not likely as it is pulled along with it by the atmosphere and the mgnetic field and not attached to the surface of the planet.
The radius of a circle is not what it seems.
Being a ball of gases or heated materials or a mixture of both, a circle is a ball of circle is a ball of circles surrounded by a ball of circles, etc. going to the center.
When you add an axis, there is a center of balance between the center to the outer ring of a circle. When rotated, this center of balance shifts towards the outer ring. This compresses and makes dense the material or gases.
Simple experiment:
One, a door. As you try to open it towards the hinge side, you need more energy to push it.
Two, A spoked wheel with a light spring and a weight closer to the center. When this is rotated, the spring compresses changing its density and incorporating energy. When allowed to be released, the enrgy slowly is released and the spring relaxes until all the energy is gone.
Now you can see how density ccan effect the atmospheres rotational abilities.
Joe
Thanx for your reply Bob. Very much appreciated.
Dear Sir;
For the first time in many efforts, I comprehended a nontrivial fraction of your post, and some others now.
The first discussion I’ve found of where the dang heat could be going while the GAT seems to be not increasing.
In a very simplistic way, the currents act somewhat like inductors, to the extent that they have reversals of flow. Equally simplistically, the water is acting capacitively, as far as soaking up the heat.
Surely much that is wrong with prior paragraph. Is there a level of model which is more simplistic than ‘zero-th’ order?
Thanks for the fine work, regardless of my blither.
RR
lgl (10:02:42):,
Very interesting. Another thing to note is the Earth’s core is also influenced by these tidal forces. That could impact geothermal output in key areas like the PWP. And, the atmosphere also is affected by these tidal forces which could explain part of what happens with the trade winds.
So may variables, so little understood …
Stephen Wilde (10:33:31),
I have to respectfully disagree. I believe Bob’s work is of primary importance. At the present time we need to focus on what has caused the recent temperature variations. If we can show that CO2=AGW is not necessary to explain the variations then we can put the issue to rest. That gives us plenty of time to go back and figure out the rest.
Note, I’m just as curious as you, as evidenced by my latest posts. However, I believe Bob’s work is the highest priority.
Bob,
I’ve noted your comment and found this.
“As noted above, the 1995/96 La Nina was not a strong event, yet it recharged all of the ocean heat that had been released in almost two decades of El Nino events.”
It’s hard to absorb the whole lot in one go 🙂
I can see the points you are making about the recharge process and the way you allocate particular periods of recharge to particular periods of release but some of the examples strain credibility.
In particular a period of recharge that was not particularly strong or lengthy is proposed to have recharged for two decades of El Nino events that were pretty substantial in themselves.
Can you be sure that the El Nino / La Nina processes combined are all that is involved here (apart from the sun that is) ?
It would explain a lot more if there were variations in the water temperatures coming from the oceanic circulations BEFORE they became involved in the ENSO process. In particular that could provide a plausible connection to the longer term climate and oceanic cycling that I have referred to.
After all a slightly less cold upwelling entering the ENSO process from below would manifest itself in warming at the surface (and vice versa) and that would help to account for the apparent disjunction between the strengths of the La Nina and El Nino phases in your article.
Richard M (12:04:09)
I agree about the importance of Bob’s work provided we can link it to the longer term climate cycles. I have often complimented Bob’s work.
As regards AGW I am already convinced that Bob’s work has helped to do the business of scotching that by helping to point out that most if not all of the 20th century temperature changes can be accounted for by oceanic and solar behaviour without invoking CO2.
That job having been done the next question is to determine how Bob’s work fits into a more general long term climate description.
The issue for me lies in deciding whether Bob’s work helps to enlighten us beyond the PDO timescale and that is where the chicken and egg problem comes in.
If it be the case that the MWP/LIA/ Modern Warm Period cycle is primarily ocean induced then it is outside Bob’s work and implies a possibility that the PDO phase shift is not merely an ENSO artifact but rather an independent feature modifying ENSO over a time scale upon which the longer term ocean cycling interacts with ENSO events.
Indeed it is plausible that longer term ocean cycles (different in each ocean) averaged out globally first affect the air circulations and then affect the Trade Winds resulting in the ENSO cycle.
Thus possibly (I’m not sure on this yet) Bob could have the causation reversed.
Bob Tisdale (08:23:37) : O/T: Bob, would you, Anthony (or someone you know!) please give a heads up on this article from RealClimate on Gamma (temperature induced) CO2 feedbacks:
http://www.realclimate.org/index.php/archives/2010/02/good-news-for-the-earths-climate-system/#more-2817
Hi Bob,
Hope to read your post in detail during the week. I have one query at this time. Have you checked the relationships between ENSO 3.4 SST anomalies, tropical Pacific SST anomalies and global tropical SST anomalies? I don’t think ENSO 3.4 anomalies are at all representative of the global tropics.
I would point out that skin temperatures at mid latitudes show a much greater temperature increase than at the equator (on a global basis) prior to and during El Nino events.
Tropical Pacific Ocean Heat content is one component of global ocean heat content. The Pacific, and what happens in local waters in its east and west is the focus of ENSO studies and these phenomena are commonly compared to the march in global temperatures but its what happens in the global ocean that is really important for temperature gain and loss on a global basis. The trades sweep waters towards the equator. If the waters outside the tropics are pre-warmed, we are actually measuring a lagged response to activity elsewhere.
There is a conundrum here. How does the ocean gain calories when its surface temperature indicates cooling?
My impression is that it is the area of the cloud free subtropical high pressure cells of descending air that is a strong variable factor explaining the change in the temperature of the in-feed waters that become the westerly currents that occupy the tropical latitudes. An increase in the cloud free area is a strong amplifying factor when tropical convection increases. If we are to get a real idea of the rate of tropical convection that drives Hadley cell dynamics and the size of the subtropical high pressure cells we need to measure the rate of evaporation from the tropical ocean. Alternatively look at temperatures at 850 hPa where the bulk of the moisture condenses or the actual areas of those high pressure cells.
Bob Tisdale:
Curious if these links has anything to do with (or can help you with) the questions you still have:
http://www-app2.gfz-potsdam.de/pb1/op/grace/
http://www-app2.gfz-potsdam.de/pb1/op/grace/results/grav/g003_eigen-cg01c.html
If not considered other acting forces we´ll remain in a flintstones´universe where everything is disconnected, made out of rounded flintstones and we can only observe if the witch sea pot it´s boiling up or it is not, we can´t go further this way.
Interesting post. 2010 will be most exciting to watch, as many trends converge. Increasing Solar Cycle 24, decreasing GCR’s, waning El Nino?, increasing CO2 and Methane.
The year has started out warm, but will it continue? Arctic Sea ice starting out like 2007 when it hit a low low summer minimum, but will it continue?
Here’s a nice chart to keep Jan. 2010 in perspective when talking about Global Temps. The dominant color on this chart is obvious:
http://iridl.ldeo.columbia.edu/maproom/.Global/.Atm_Temp/Percentiles.html
But was that El Nino driven? And if not, then what?
Ref – Pascvaks (12:53:08) :
Bob Tisdale:
“Curious if these links HAVE anything to do with (or can help you with) the questions you still have:”
_____________
Here’s another version, this one’s flat
http://veimages.gsfc.nasa.gov/16527/PIA04652_lrg.jpg
lgl (10:02:42) :
I have suggested a Lunar connection. Eclipses give extra tidal forces and when hitting low latitudes mass will get pulled towards the equator. This could change currents (atmos and ocean) either directly or via changing earth’s rotation. http://virakkraft.com/uah-rss-moon.png
There are longer term lunar cycles which may be linked to oceanic changes too.
http://tallbloke.wordpress.com/2009/11/30/the-moon-is-linked-to-long-term-atlantic-changes/
However Paul Vaughan warns there may be a counfounding issue with a similar length solar cycle.
lgl (09:46:12) :
tallbloke (08:13:12) :
Another interesting question is why didn’t all the other La-Ninas cause steps in OHC, why only the 75 and 95 Ninas? LOD changed from increasing to decreasing around 73 and 93 so I’ll bet those changes in earth rotation are the real cause of the step ups. Then all we need to get a cooling phase is a flip back to increasing LOD.
An early indicator could be a change in the rate the north magnetic pole is moving:
http://tallbloke.wordpress.com/2009/12/11/north-pole-position-shifts/
It looks like there could be a short term shift around 2017, but it’s a tough one to call
Ref – Pascvaks (12:53:08) :
Bob Tisdale:
“Curious if these links…”
_________________
Curious how close magnetism and gravity match up. Heres a dated (2000) global declination diagram. Know you’ve probably considered all this, but just in case…
http://www.cas-cozy.nl/efis/images/HMR3000/variation%20magnetic.gif
Kevin Kilty: Many thanks for your insightful comment. Unfortunately, every post I write on ENSO cannot include all facets of it. You paraphrased my post and asked me to comment. You wrote, “ENSO is a heat engine. It absorbs heat from sunlight in the tropics, converts this to work needed to transport warm water all over the Pacific and Indian oceans, and then expels waste heat in higher latitudes. This waste heat exhibits itself as anomalously high lower tropospheric temperatures in polar and temperate regions — and this raises global mean temperature.”
The comparison of ENSO to a heat engine brought back memories. It reminded me of a series of posts written about a decade ago, by NASA or NOAA or a college. Wish I could find it. It was a year or so after the 1997/98 El Nino.
Regardless, a few clarifications if I may. There are numerous papers written about ENSO discharge and recharge. La Nina is the recharge phase. It allows more sunlight to warm the tropical Pacific. The increased trade winds carry that warm water to the Pacific Warm Pool and also return to the west any remaining warm water that had been released by the El Nino. Some of this warm water will be carried poleward by surface currents, or to the Indian Ocean by way of the Indonesian Throughflow. The warm water carried poleward during the La Nina will continue to release heat. During the El Nino, the discharge phase, warm water that had been stored in the Pacific Warm Pool sloshes to the east where it spreads across the surface, raising sea surface temperatures in the tropical Pacific. On the surface, it releases more heat than normal, which is carried poleward by normal atmospheric processes. However, since the location of the warm water has changed, so has the area with the convection. This change also shifts global atmospheric circulation patterns, causing rises in surface temperatures outside of the tropical Pacific.
You continued, “Now in order to explain how a cyclic engine manages to produce semi-permanent step increases and/or secular trends in temperature, something about the engine is causing it to run in a larger enclosed area…”
It’s really not a semi-permanent step. It appears so because of the focus on the El Nino as the discharge phase, but in reality the warm water released by the El Nino remains on the surface during the La Nina phase. This can be seen in a graph of the SST anomalies for an area in the Northwest Pacific that’s east of Japan known as the Kuroshio Extension…
http://i48.tinypic.com/2eb5log.png
Note that the lagged rise in SST anomalies is approximately 40% as high as the rise in NINO3.4 SST anomalies during the El Nino, but that the rise in the Kuroshio Extension SST anomalies occurs during the La Nina. The North Atlantic (not illustrated) also governed by the Atlantic Multidecadal Oscillation, which had caused the North Atlantic SST anomalies to rise at a rate more than 2 times faster than the global SST anomalies…until ~2005. The North Atlantic SST anomalies now appear to be dropping in response to a shift in the AMO.
And the engine, as you call it, runs in a larger enclosed area because ocean currents and atmospheric circulation carry the heat toward the poles, with the majority going to the Northern Hemisphere. Since the SST anomalies and TLT anomalies of the Northern Hemisphere rose in response to the 1997/98 El Nino and portions rose during the La Nina that followed, it gives the appearance of a permanent upward step. But with the SST anomalies of the North Atlantic now dropping in response to the AMO, will the appearance of upward steps continue? We’ll have to watch and see.
Kevin, please let me know if that answered your questions.
Interesting post.
This makes the La Nina the equivalent of the boiler phase.
The West Coast of the US gets huge amounts of rain during El Nino years, transferring huge amounts of heat to space from the oceans via condensing water vapor. During La Nina years, this heat transfer does not occur.
O/T – but I’ve been looking at fisheries catches. Then started looking at proxies for fisheries biomass.
First, catches:
Looking at Fisheries catches is another way to see long-term La Nina/El-Nino effects. The biomass production of both has a very strong feedback effect dependent totally on La-Nina driven cold water upwelling. Sardines are more temperature sensitive that Anchovies – the Sardines thriving during warmer conditions.
http://www.fao.org/docrep/005/y2787e/y2787e3a.gif
Now, biomass production going back to 300 AD.
http://ucce.ucdavis.edu/files/repository/calag/fig5104p38.jpg
The above graph has some very interesting cycles. You can clearly see the effects of the LIA and the MWP.
Caleb: You wrote, “I’d like to know more about what makes the Trade Winds stronger, and what makes them weaker, because it seems to be the difference between the Pacific ‘recharging’ or ‘discharging.'”
Have you read Bill Kessler’s FAQ web page on ENSO? It provides a not-to-technical discussion of the coupled ocean-atmopsphere processes associated with El Nino and La Nina events.
http://faculty.washington.edu/kessler/occasionally-asked-questions.html
JP: You wrote, “We just don’t have the means to accurately measure such things.”
The NOAA TAO Project has had buoys collecting atmospheric, sea surface and subsurface data in the tropical Pacific since the late 1970s/early 1980s.
Richard M (09:21:09) : You wrote, “The big question still remains. What causes ENSO in the first place. The trade winds could be an effect of ENSO with the PWP heat rising leading to the trades increasing. Also, what causes the variation in El Nino (Modoki).”
ENSO processes are well understood. Refer to Bill Kessler’s FAQ web page for an overview:
http://faculty.washington.edu/kessler/occasionally-asked-questions.html
El Nino Modoki are discussed in great detail (78 pages worth) in Ashok et al (2007) “El Nino Modoki and its Possible Teleconnection.” https://www.jamstec.go.jp/frcgc/research/d1/iod/publications/modoki-ashok.pdf
Regards
Stephen Wilde (10:33:31) : You wrote, “I wish you would apply your attention to what drives or triggers ENSO and/or PDO because that is where climate truth resides.”
My research of and attention toward ENSO have been to explain the rise in global temperatures since 1975. Nothing more, nothing less.
You wrote, “The NOAA link is not helpful in that respect nor was the reply to stephen richards.”
Try Google.
You wrote, “The fact is that there appears to be an ocean driven cycle from MWP to LIA to the Modern Warm Period and we need to bridge the gap from your ENSO work to that longer term cyclical phenomenon.”
Do you have data to support this claim? Also, I have no interest in the MWP or LIA. You do.
You wrote, “Unless we can do that then regrettably all your work is of little value in terms of the background climate changes upon which ENSO is superimposed.”
Again, my work helps explain the natural rise in global temperatures since 1975. Please identify and document, using data, the percentage of that that you attribute to the “ocean driven cycle from MWP to LIA to the Modern Warm Period” you refer to. And as I constantly remind you, without data, your comments are conjecture.
You wrote, “ENSO itself is of little value if it can only deal with shorter term climate variability.”
That’s all I concern myself with, short-term climate variability, because data (something you do not rely on) is available for short-term analysis.
You concluded with, “I’m trying to help you here.”
You refer to my post with phrases like “logical inconsistency” and “the unlikeliness of that proposition” and state that you’re trying to help. Yet you missed the topic of the post and appear to have misunderstood what I had written.
Adios, Stephen.