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Keep in mind that the following discussion is based on preliminary monthly OI.v2 Global and NINO3.4 SST anomaly data. The weekly data, though, is official. The official monthly values will be posted by NOAA on December 6, 2009, so check back in a week.
NINO3.4 SST anomalies rose 0.63 deg C during November 2009 to 1.67 deg C.
Actually, I do understand what was done. And, as I’ve illustrated and discussed in a number of posts, the relationship between ENSO and Global Temperature is NOT LINEAR, so the methods employed in Thompson et al (2009) cannot be used to remove the impact of ENSO from global temperature. I discussed this in great detail in my recent post “More Detail On The Multiyear Aftereffects Of ENSO - Part 2 – La Nina Events Recharge The Heat Released By El Nino Events AND...” In it I provide quotes from Trenberth et al (2002) "Evolution of El Nino–Southern Oscillation and global atmospheric surface temperatures”, to support my presentation of the relationship between ENSO and Global Temperatures.
Note that the Jones link to the Thompson et al (2009) preprint no longer works.
The east-west dipole in the tropical Pacific and its carryover into the Eastern Indian is well known. Refer to Figure 1, which is a .gif animation of global SST anomaly maps for the peak of the 1997/98 El Nino and the peak of the 1998/99 La Nina, the first ENSO season of the 1998/99/00/01 La Nina. Note how the SST anomalies of the East Indian and West Pacific oceans rise when the East Pacific SST anomalies drop in response to the La Nina. The methods used by Thompson et al (2009) neglect this rise in the SST anomalies for 25% of the global oceans (between 60S and 65N) during the multiyear La Nina event.
The effect of the east-west dipole is also very easy to see in a comparison graph of East Pacific SST anomalies and the SST anomalies of the East Indian and West Pacific Oceans, Figure 2. Note how the opposing responses of the two datasets to the major traditional ENSO events are similar in magnitude. Yet, somehow, climate researchers attempt to remove the effects of ENSO by subtracting scaled and lagged NINO3.4 or Cold Tongue Index (CTI) data from global temperatures, even though the SST anomalies of a large portion of the global oceans reacted in the opposite direction to the change in SST anomalies of the ENSO index. http://i50.tinypic.com/28ro7kk.png
Figure 2
I wonder what wrong assumptions he claims I’m making! One thing is sure: I’m not the one assuming the relationship between ENSO and global temperature is linear, when the instrument temperature record clearly shows it’s not. Jones could use the Hadley Centre’s HADSST2 or HADISST or the NCDC’s ERSST.v2 or ERSST.v3b to reproduce the SST anomaly graphs I’ve presented in “More Detail On The Multiyear Aftereffects Of ENSO - Part 2 – La Nina Events Recharge The Heat Released By El Nino Events AND...”. The results are the same.
I’m also not the one who assumes that greenhouse gases have a noticeable effect on tropical Pacific Ocean Heat Content, when the NODC (Levitus et al – 2009) OHC data clearly shows decadal and multidecadal declines, with recharges during multiyear La Nina events. Figure 3. This was discussed in detail and illustrated in the post linked twice above and linked once again, “More Detail On The Multiyear Aftereffects Of ENSO - Part 2 – La Nina Events Recharge The Heat Released By El Nino Events AND...”. The Sources of the data used to create the illustrations in this post are listed at the end of that post. http://i36.tinypic.com/eqwdvl.png
Figure 3
It will hopefully fill in some of the gaps left by my earlier discussions on the long-term effects of major traditional El Nino/La Nina events.
I will not be at my computer for long stretches today, I've got visitors, so I will not be moderating comments quickly or responding to questions until tomorrow.
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...During Major Traditional ENSO Events, Warm Water Is Redistributed Via Ocean Currents.
INTRODUCTION
This is Part 2 of a multipart post. It addresses critical comments about my earlier posts that dealt with the multiyear aftereffects of major traditional El Nino events. Two specific El Nino events, those in 1986/87/88 and 1997/98, caused Sea Surface Temperatures (SST) of the East Indian and West Pacific Oceans to remain at elevated levels during the subsequent La Nina events. These SST residuals, what I have called step changes in earlier posts for the sake of simplicity, bias global SST upward during the La Nina events and give the impression of a gradual increase, one that is attributed to anthropogenic greenhouse gases.
This post differs from earlier posts in that:
1. I’ve included discussions and illustrations from Pavlikus et al (2008) “ENSO Surface Shortwave Radiation Forcing over the Tropical Pacific” and presented ISCCP Cloud Amount Anomaly Maps to illustrate the locations of the cloud amount variations over the Tropical Pacific,
2. I’ve illustrated and discussed the dipole effect of El Nino events on portions of the Indian and Pacific Oceans,
3. I’ve discussed and illustrated the warm water redistribution aspect of El Nino and La Nina events, and,
4. I’ve included illustrations and quotes from Trenberth et al (2002) "Evolution of El Nino–Southern Oscillation and global atmospheric surface temperatures” to confirm my presentation and discussions of ENSO and its impacts on SST.
Trenberth et al (2002) briefly describes how La Nina events recharge the heat that had been discharged and redistributed from the tropical Pacific during El Nino events. On page 16, paragraph 57 they write, “The negative feedback between SST and surface fluxes can be interpreted as showing the importance of the discharge of heat during El Nino events and of the recharge of heat during La Nina events. Relatively clear skies in the central and eastern tropical Pacific allow solar radiation to enter the ocean, apparently offsetting the below normal SSTs, but the heat is carried away by Ekman drift, ocean currents, and adjustments through ocean Rossby and Kelvin waves, and the heat is stored in the western Pacific tropics. This is not simply a rearrangement of the ocean heat, but also a restoration of heat in the ocean.”
Note that the area referenced with “west Pacific tropics” is the Pacific Warm Pool.
In short, the La Nina restores the heat discharged and redistributed by the El Nino. This can be illustrated with a comparison graph of NINO3.4 SST anomalies and Ocean Heat Content (OHC) of the tropical Pacific, Figure 1. The discharge and recharge can be seen if you focus on the 1972/73, 1986/87/88, and 1997/98 El Nino events. Those three major El Nino events also are not impacted to any significant extent by volcanic aerosols.
The recharge is accomplished by changes in cloud amount. The “relatively clear skies” in the above quote from Trenberth et al refers to the decrease in cloud amount during the La Nina phase of ENSO. The coincidence between NINO3.4 SST anomalies and Tropical Pacific Cloud Amount can be seen in a comparison graph, Figure 2. http://i35.tinypic.com/4rxele.jpg
Figure 2
And to quote Trenberth again, “Relatively clear skies in the central and eastern tropical Pacific allow solar radiation to enter the ocean, apparently offsetting the below normal SSTs…” So it’s an increase in Downward Shortwave Radiation (due to the decrease in cloud amount) that recharges the tropical Pacific OHC.
Trenberth et al did not quantify the amount of heat restored during the La Nina phase, but if you’d like an order of magnitude for the amount of heat discharged, redistributed, and recharged during major El Nino and La Nina events, you could look at the comparison graph of NINO3.4 SST anomalies and Tropical Pacific OHC, Figure 1, and again key off the 1972/73, 1986/87/88 and 1997/98 El Nino events.
CLOUD AMOUNT ASPECT OF ENSO RECHARGE PHASE IS DISCUSSED IN PAVLAKIS ET AL (2008)
In “ENSO Surface Shortwave Radiation Forcing over the Tropical Pacific” (2008), Pavlakis et al illustrated the inverse relationship between NINO3.4 SST anomalies and Downward Shortwave Radiation (visible light) anomaly (DSR-A) at the surface of the Central and Eastern Tropical Pacific: http://www.atmos-chem-phys-discuss.net/8/6697/2008/acpd-8-6697-2008-print.pdf
The Pavlakis et al Figure 6 is shown here as Figure 3. It compares NINO3.4 SST anomalies and Downward Shortware Radiation (DSR), which is visible light, for two areas of the Central and Eastern Tropical Pacific. Note how, when NINO3.4 SST anomalies are negative, indicating a La Nina, DSR anomalies are positive, indicating that more sunlight is reaching and entering the Central and Eastern Tropical Pacific Ocean, warming it. The opposite happens during an El Nino: NINO3.4 SST anomalies are positive and DSR anomalies are negative, indicating that less visible light is warming the Central and Eastern Tropical Pacific Ocean. Keep in mind, though, that during the El Nino phase, while there may be less sunlight entering the Central and Eastern Pacific Ocean, this is happening during the discharge phase of ENSO. http://i47.tinypic.com/eqs7d3.png
Figure 3
Some might find the Pavlakis et al Figure 1 informative. It illustrates, “The distribution of downward shortwave radiation at the surface (DSR), over the tropical and subtropical Pacific for the three month period November, December, January (NDJ); (a) eleven neutral years average, (b) average for five El Nino years, (c) average for five La Nina years.” I’ve animated the individual cells of their Figure 6 in my Figure 4. (Pavlakis et al detail the source of Figure 4 (Their Figure 6) on page 4, under the heading of “Long-term surface shortwave radiation.”) http://i48.tinypic.com/2a9cxfq.gif
Figure 4
Cell a (ENSO Neutral): http://i49.tinypic.com/27ytmc8.png
Cell b (El Nino): http://i47.tinypic.com/vsmkd4.png
Cell c (La Nina): http://i49.tinypic.com/1gg07s.png
ISCCP TOTAL CLOUD AMOUNT ANOMALY MAPS ALSO ILLUSTRATE THE ENSO-CAUSED VARIATIONS
ISCCP Cloud Amount data used by Pavlakis et al are available through the KNMI Climate Explorer. Figure 5 illustrates maps of the Average Total Cloud Amount Anomalies for the Tropics for the months of November to January. These months were chosen because these are typically when ENSO events peak. The maps begin with the 1996/97 season, Cell A. There were ENSO-neutral conditions in 1996/97; NOAA ONI Index data were slightly negative
(-0.3 to -0.4 deg C). Cell A captures the negative cloud amount anomalies over the central tropical Pacific a year before the peak of the 1997/98 El Nino. Recall that the negative Total Cloud Amount anomalies indicate that DSR is positive. Then, during the peak months of the 1997/98 El Nino, Cell B, the Total Cloud Amount Anomalies are elevated over the central tropical Pacific, indicating that the convection and cloud cover has followed the warm water eastward during the El Nino. At this point, the central and eastern tropical Pacific are releasing large amounts of heat to the atmosphere. Note also that the Total Cloud Amount anomalies have dropped significantly over the western tropical Pacific and the eastern tropical Indian Ocean. This indicates that the Pacific Warm Pool is being recharged by DSR during the El Nino. Cell C shows the Total Cloud Amount Anomalies during the initial peak of the 1998/99/00/01 La Nina. Cloud Amount Anomalies are negative over the central and eastern Tropical Pacific, indicating the recharge of the heat released and redistributed during the El Nino. This pattern continues during the peak seasons of 1999/00 and 2000/01, Cells D and E. Cell F illustrates the Cloud Amount Anomalies of the ENSO-neutral 2001/02 season. http://i46.tinypic.com/t6ccpe.png
Figure 5
IS THERE EVIDENCE OF AN IMPACT OF ANTHROPOGENIC GREENHOUSE GASES ON THE RECHARGE MODE OF ENSO?
The next logical point to address would be how much of the ocean heat recharge could be attributed to the constantly increasing infrared radiation from Anthropogenic Greenhouse Gases and how much could be attributed to the rise in visible light from the decrease in cloud amount during La Nina events. This raises the debate about the impacts of infrared radiation and visible light on Ocean Heat Content. Downward Shortwave Radiation (DSR), which is visible light, penetrates and warms the ocean for 100+ meters, while infrared radiation or Downward Longwave Radiation (DLR) only penetrates the top few centimeters. So the order of magnitude of the temporary increase in DSR (visible light) is many times greater than the long-term increase in DLR (infrared radiation) from greenhouse gases. But the argument has been presented that DLR (infrared radiation), through mixing caused by waves and wind stress turbulence, would warm the mixed layer of the ocean. This in turn would impact the temperature gradient between the mixed layer and skin, dampening the outward flow of heat from the ocean to the atmosphere. The end result according to the argument: OHC would rise due to an increase in DLR (infrared radiation) caused by increases in greenhouse gas emissions.
However, refer to the Tropical Pacific OHC data, Figure 1, again. While there is no doubt that there is a positive trend in the Tropical Pacific OHC data, the graph shows decadal and multidecadal periods of decreasing OHC. During these periods, the heat released and redistributed by the El Nino events is not replaced fully by the La Nina events. If it was, OHC trends would be flat, instead of declining. What the graph does NOT show is a gradual rise in Tropical Pacific OHC as one would expect if greenhouse gases had an influence. Also note that the heat lost during these long-term decreases is replaced and additional heat is added during two multiyear periods. Those two periods coincide with the multiyear La Nina events of 1973/74/75/76 and 1998/99/00/01. In other words, these two multiyear La Nina events add more heat than is necessary to replace the heat lost over the decadal and multidecadal periods. Without those two multiyear La Nina events, the long-term trend in Tropical Pacific OHC would be negative.
Describing the OHC anomalies in Figure 1 in more detail, for the decade from 1963 to 1973, OHC anomalies dropped gradually from ~0.04 GJ/m^2 to ~-0.3 GJ/m^2, and for the two decades from 1977 to 1997 (1999), OHC anomalies dropped gradually from ~0.16 GJ/m^2 to ~-0.12 GJ/m^2 (~-0.16 GJ.m^2). During the multiyear (4-year) period between them, from 1973 to 1977, OHC anomalies rose from ~-0.3 GJ/m^2 to ~0.16 GJ/m^2; this appears to be a recharge caused by the multiyear 1973/74/75/76 La Nina.
The curious 1995/96 upsurge in tropical Pacific OHC was explained in McPhaden (1999) “Genesis and Evolution of the 1997-98 El Nino.” It is the result of “stronger than normal trade winds associated with a weak La Nina in 1995–96.” http://www.pmel.noaa.gov/pubs/outstand/mcph2029/text.shtml
The stronger trade winds reduce cloud amount, which, in turn, allows more DSR to warm the ocean. The stronger trade winds also feed that warm water to the Pacific Warm Pool at an elevated rate.
With that anomalous rise in Tropical Pacific OHC in 1995/96, it could be argued that the increase in tropical Pacific OHC of ~-0.08 GJ/m^2 to ~0.24 GJ/m^2 from 1998 to late 2001 was a rebound to the values established by the 1995/96 La Nina, or it could be argued that the rise in tropical Pacific OHC was caused by the multiyear 1998/99/00/01 La Nina, similar to the 1973/74/75/76 La Nina. Regardless, the data does not support the argument that Tropical Pacific OHC rises due to an increase in DLR (infrared radiation) caused by increases in greenhouse gas emissions.
THE RESPONSE OF GLOBAL TEMPERATURES TO EL NINO EVENTS ARE NOT COUNTERACTED BY LA NINA EVENTS
It is often assumed that the effects of El Nino events on global temperatures are countered by La Nina events. That is, an El Nino is known to cause an increase in global temperature, but it is assumed that a La Nina event causes a proportional decrease in global temperature. SST anomalies for many of the ocean basins, or portions thereof, do agree with the assumption. They show comparable responses to La Nina events. Refer to Figures 6 through 8. These are comparison graphs of scaled NINO3.4 SST Anomalies and the SST anomalies of the ocean basins where El Nino and La Nina events have similar effects. http://i33.tinypic.com/w8w1hg.jpg
Figure 6
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Figure 7
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Figure 8
However, there is a major portion of the global oceans where El Nino and La Nina events have the opposite effect on the SST anomalies. This area is well known, as is the effect. During El Nino events, Eastern Tropical Pacific SST anomalies rise, and at the same time, SST anomalies in the Western Tropical Pacific and Eastern Indian Oceans fall. During La Nina events, the opposite holds true: SST anomalies in the Eastern Tropical Pacific drop and they rise in the Western Tropical Pacific and Eastern Indian Oceans. The seesawing between the Eastern and Western Pacific SST anomalies is known as a dipole effect. This seesaw relationship can be seen in the global SST anomaly maps during El Nino and La Nina events. Refer to Figure 9, which illustrates SST anomalies near the peak of the 1997/98 El Nino and near the first seasonal peak of the 1998/99/00/01 La Nina. http://i48.tinypic.com/xc6s0l.gif
Figure 9
In fact, one phase of the opposing relationship between the SST Anomalies of the Eastern Pacific and the SST Anomalies of the Western Pacific and East Indian Oceans can be seen in the Trenberth et al sequence of lagged correlations of NINO3.4 with surface temperatures. Refer to their Figure 8, which is presented here as my Figure 10. The left-hand maps illustrate the lag correlations for the period of 1950 to 1978 and the right-hand column depicts the same for 1979 to 1998. (Trenberth et al were illustrating the differences in the evolution of El Nino events between the two periods.) I’ve highlighted the correlations at zero-month lag. The basic dipole pattern appears in both the 1950 to 1978 and 1979 to 1998 periods of the Trenberth et al Figure 8, my Figure 10. This is not an effect that is unknown. http://i47.tinypic.com/261e1lf.png
Figure 10
Figure 11 is a comparison of East Pacific SST anomalies and the SST Anomalies of the East Indian and West Pacific Oceans. I’ve also included scaled NINO3.4 SST anomalies as a reference for timing. The 1986/87/88 and 1997/98 El Nino events and the initial portions of the subsequent La Nina events are highlighted. It is very clear that the two datasets are out of phase. http://i49.tinypic.com/24bm92u.png
Figure 11
Figure 12 is the same comparison graph, but in it, I’ve highlighted a different portion of the data. The response of the East Pacific SST anomalies to the major El Nino events of 1986/87/88 and 1887/98 is very visible in that comparison graph. But note how little the SST anomalies of the East Indian and West Pacific drop (the area highlighted) while the SST anomalies in the East Pacific are rising dramatically. This happens because traditional El Nino events are fueled by subsurface waters from the Western Tropical Pacific, from depths to 300 meters in the Pacific Warm Pool. These subsurface waters are not included in SST measurements. http://i47.tinypic.com/6zvkte.png
Figure 12
OCEAN CURRENTS TRANSPORT WARM WATER OUT OF THE TROPICAL PACIFIC
Figure 13 is the comparison graph of East Pacific SST anomalies and the SST Anomalies of the East Indian and West Pacific Oceans once again, but in this instance, I’ve highlighted the periods during which the SST anomalies of the East Indian and West Pacific Oceans diverge greatly from the variations in the East Pacific SST anomalies (which are correlated with NINO3.4 SST anomalies). http://i50.tinypic.com/28ro7kk.png
Figure 13
Much of the East-West dipole effect between the East Pacific and the East Indian-West Pacific is caused by the movement of warm water within the Pacific Basin. During the formation of El Nino events, a Kelvin Wave carries warm water east. Note the eastward progression of Sea Surface Height anomalies along the equatorial Pacific illustrated in Figure 14. http://i49.tinypic.com/21afqzd.jpg
Figure 14
And during the La Nina, warm water is carried west by a Rossby wave that forms in the eastern Tropical Pacific north of the equator. This is illustrated in Figure 15 with the progression of Sea Surface Height anomalies from east to west. http://i50.tinypic.com/2jewitd.jpg
Figure 15
The transport of warm water from west to east during the 1997/98 El Nino formation and from east to west during the 1998/99 portion of the subsequent La Nina can also be seen quite plainly in the Sea Level Residual animation from JPL, starting at about 50 seconds into the video. (The video in mpeg format is linked above.) Let the video continue after the Kelvin and Rossby waves associated with the 1997/98 El Nino and watch how long the Sea Level Residuals in the East Indian and West Pacific Oceans remain elevated after that ENSO event.
Wind-driven ocean currents also change during El Nino and La Nina phases. During the 1997/98 El Nino, the Equatorial Countercurrent in the Pacific increases in flow, Figure 16. This carries warm water from the western Tropical Pacific to the east. And during the La Nina, the flow of the Equatorial Countercurrent in the Pacific has decreased; the North and South Equatorial Currents dominate then and carry warm water back to the western Tropical Pacific. http://i50.tinypic.com/nvqoex.png
Figure 16
Note also in Figure 17, that there is a current that flows from east to west through the Indonesian Archipelago, north of Australia, from the Tropical Pacific to the Tropical Indian Ocean. That current is called the Indonesian Throughflow. After the warm water has been returned west after the El Nino event, the Indonesian Throughflow carries it into the Tropical Indian Ocean.
Note that there are a great number of coupled ocean-atmosphere processes taking place within the Pacific Ocean before, during, and after ENSO events. The above explanation using ocean currents is very simple. Those in search of more detailed discussions could start with the references in Trenberth et al (2002).
And there will be those looking for confirmation that ocean currents redistribute warm waters that have been released by the El Nino. Trenberth et al write (page 13, paragraph 37) [My caps for emphasis], “The evolution of ENSO in the tropical Pacific Ocean illustrated here supports much of that previously described by Barnett et al. [1991], Zhang and Levitus [1996], Tourre and White [1995], Giese and Carton [1999], Smith [2000], and Meinen and McPhaden [2000] in the way that anomalies of subsurface ocean heat content in the western Pacific develop as they progress eastward across the equatorial Pacific, often with a dipole pattern across the Pacific, AND THEN WITH ANOMALIES PROGRESSING OFF THE EQUATOR TO HIGHER LATITUDES. Zhang and Levitus [1996] found links only to the North Pacific, perhaps reflecting the available data, while our results reveal strong links to both hemispheres. The SST evolution lags somewhat behind that of the subsurface ocean and is damped by surface fluxes and transports out of the region by the atmosphere, emphasizing the dominant role of the surface wind stress and ocean dynamics and advection in producing the local ocean heat content and SST anomalies. This damping of the ocean signal, however, forces the atmospheric anomalies. MOREOVER, THIS ASPECT ALSO EMPHASIZES THAT IN COLD LA NINA CONDITIONS THE SURFACE FLUXES OF HEAT ARE GOING INTO THE OCEAN RELATIVE TO THE MEAN AND ARE WARMING THE OCEAN, ALTHOUGH NOT LOCALLY AS THE HEAT IS REDISTRIBUTED BY CURRENTS.”
SUMMARY
As discussed in the preceding, the warm water that fuels a traditional El Nino is stored in the Pacific Warm Pool. This warm water was “supplied” by the prior La Nina event. During an El Nino, that warm water travels east and is spread across the surface of the Eastern Tropical Pacific. Then during the La Nina that follows, the warm water is transported to the Western Tropical Pacific, where it is carried poleward and to the Eastern Indian Ocean by ocean currents. At the same time, during the La Nina, cloud cover over the Tropical Pacific decreases and Downward Shortwave Radiation (DSR) increases, warming the ocean surface more. Ocean currents carry this water to the Western Tropical Pacific, where it recharges the Pacific Warm Pool. At the end of the complete cycle of El Nino (discharge) and La Nina (redistribution and recharge), the Ocean Heat Content of the Tropical Pacific is restored (Figure 1) and sea surface temperatures have been raised.
In other words, Tropical Pacific Ocean Heat Content is regulated by the discharge, redistribution, and recharge of heat during El Nino and La Nina events. The heat that is released and the warm water that is redistributed during the traditional El Nino are “replaced” by the increase in Downward Shortwave Radiation during the La Nina. It appears that the redistribution of warm water during the La Nina and its impact on atmospheric circulation are overlooked when climate researchers attempt to account for the effects of ENSO on global temperatures, since they do not consider the dipole effect that takes place within the Pacific when they attempt to remove the effects of ENSO from global temperatures. Climate researchers assume the relationship between ENSO and global temperature is linear, when it clearly is not.
Figures 11 through 13 presented comparison graphs of East Pacific SST Anomalies and the SST Anomalies of the East Indian and West Pacific Oceans. For Figure 18, I’ve combined those two datasets and plotted them, listing them as East Indian and Pacific SST Anomalies. Assume for example that an ENSO event in total includes the combined effects of the El Nino and the subsequent La Nina, because the warm water released during the traditional El Nino continues to be redistributed during the La Nina. I’ve highlighted the points in Figure 18 at which the SST anomalies “equalize” before and after the major traditional El Nino events of 1986/87/88 and 1997/98 and their resulting La Nina events. I’ve also noted the approximate SST anomalies at those times. Over the multiyear period between the two ENSO events, SST anomalies for the combined East Indian and Pacific data (red) have remained relatively flat. They rose only ~0.02 deg C, from ~0.1 to 0.12 deg C, between mid-1990 and late 1996. And during the multiyear period after the 1997/98 and 1998/99/00/01 La Nina, SST anomalies have declined. http://i48.tinypic.com/2enz2ac.png
Figure 18
But during the multiyear period of the 1986/87/88 El Nino and the 1988/89 La Nina, the East Indian and Pacific SST anomalies rose ~0.17 deg C, from ~-0.07 to ~0.1 deg C. And during the period of the 1997/98 El Nino and 1998/99/00/01 La Nina, the SST anomalies for the combined East Indian and Pacific dataset increased ~0.1 deg C, from ~0.12 to ~0.22 deg C. SST anomalies for the periods between and after major traditional ENSO (El Nino and La Nina) events either remain flat or they decline. But they rise during those major traditional ENSO (El Nino and La Nina) events. This is not a simple coincidence; causation is known.
I presented a number of reasons why the ENSO residuals (the apparent step changes) in the SST anomalies of the East Indian and West Pacific SST anomalies were important at the conclusion of my post “Global Temperatures This Decade Will Be The Warmest On Record…”. I’ll reproduce one here. Note that I’ve changed the Figure numbers for this post.
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The step changes bias the global SST anomalies upward and give the impression of a gradual increase in SST anomalies. This can be seen in a comparison graph of the SST anomalies of the East Indian and West Pacific Oceans, the SST anomalies of the “Rest of the World” (East Pacific, Atlantic, and West Indian Oceans), and the combination of the two, Figure 19. The period since 1996 is unique in the last 40+ years. There haven’t been any major volcanic eruptions to add noise to the data. This is why the data in Figure 19 starts in 1996. http://i38.tinypic.com/2ezjk9s.png
Figure 19
Note how in Figure 19 the East Indian and West Pacific SST anomalies linger at the elevated levels while the SST anomalies for the “Rest of the World” are mimicking the variability of the NINO3.4 SST anomalies, shown in part in Figures 6 through 8. (That is, the SST anomalies for the “Rest of the World” are responding as researchers expect to both El Nino and La Nina events.) Over the next few years, ocean currents “mix” the elevated SST anomalies of the East Indian and West Pacific Oceans with the depressed SST anomalies of the “Rest of the World” oceans, dropping one and raising the other, until they intersect in 2003. This is more than 4 years after the end of the 1997/98 El Nino. Because the Global SST anomalies are a combination of the two, they are biased upward by the elevated East Indian-West Pacific SST anomalies and by the mixing with the waters of the “Rest of the World”. This gives the false impression of a gradual increase in global SST anomalies.
In other words, the effects of the major traditional El Nino events can linger for at least 4 years, causing gradual increases in global sea surface temperatures during that time. This gradual increase is incorrectly attributed to anthropogenic sources.
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Note that Trenberth et al (2002) serves as a wonderful resource when studying the effects of ENSO on global climate. However, the paper was written in 2000, published in 2002, and the data used in it stops in 1998. As illustrated above, the long-term effects of major traditional El Nino/La Nina events are best illustrated over the period of 1997 through 2001, because there were no volcanic eruptions to add noise to the data. Obviously, Trenberth et al could not have captured or discussed the long-term effects of that El Nino/La Nina event.
Also note that climate researchers attempt to remove the effects of ENSO events on global temperatures by subtracting scaled NINO3.4 SST anomalies (or another ENSO index) from global temperatures. They claim the rise in global temperatures that remains is caused by anthropogenic greenhouse gases. Refer to Figure 20. It should now be very clear that any attempt to remove the effects of ENSO in this way misses this dipole (seesaw) effect on the East Indian and West Pacific Ocean SST anomalies. One might think then that an index based on the SST anomalies of the East Indian and West Pacific Oceans could be created to capture this dipole effect and that this new index could be used to remove its linear portion from the global temperature record. Unfortunately, this will not work, because ocean currents and other coupled ocean-atmosphere processes “blend” the ENSO and dipole effects with other ocean basins. It also would not capture the effects of the warm waters that are supplied by the Pacific Warm Pool, which are not included in the SST anomalies before the El Nino event. Also, ENSO events are not created equal, and the response of global climate to ENSO events differs. Many El Nino events are pseudo-El Nino events, known as El Nino Modoki, and the response of global climate to El Nino Modoki are different that the response to traditional El Nino events. Refer to Ashok et al (2007) “El Nino Modoki and its Possible Teleconnection.” https://www.jamstec.go.jp/frcgc/research/d1/iod/publications/modoki-ashok.pdf http://i34.tinypic.com/3589pj9.png
Figure 20
The papers that use this erroneous method are listed toward the bottom of my post Global Temperatures This Decade Will Be The Warmest On Record…, under the heading of “Papers That Portray A Linear Relationship Between ENSO And Global Temperatures”.
One last note, Trenberth et al (2002) acknowledged the existence of the residual effects of ENSO events. They wrote, “Although it is possible to use regression to eliminate the linear portion of the global mean temperature signal associated with ENSO, the processes that contribute regionally to the global mean differ considerably, and THE LINEAR APPROACH LIKELY LEAVES AN ENSO RESIDUAL.” [My caps for emphasis.]
And as illustrated in this post, the ENSO residuals from the 1986/87/88 El Nino and 1988/89 La Nina and from the 1997/98 El Nino and 1998/99/00/01 La Nina, account for most of the rise in global SST anomalies from 1981 to 2009, excluding the North Atlantic, of course, which is dominated by the Atlantic Multidecadal Oscillation).
SOURCES
In addition to the sources noted throughout the text, the others are listed below.
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The following graph of global temperature anomalies is from the “The Copenhagen Diagnosis, 2009: Updating the world on the Latest Climate Science.” The report was released today with obvious intent. I scrolled as far as Figure 3, then copied it, and closed “The Copenhagen Diagnosis”. I’d had enough. Please feel free to answer the question asked in the title of this post.
UPDATE (November 25, 2009): In the comments, Alessandro noticed what I did. He wrote, “The smoothing is not declared and probably the final part ('2000) is corrected.” But I will make my case that those smoothed curves are trends of some sort.
As Alessandro mentioned, they don’t identify the smoothed data. Do the smoothed curves represent filtered data or polynomial trends? If you were to look at the long-term surface temperature anomaly graphs (land, sea, and combined) in Chapter 3 of the IPCC AR4… http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch03.pdf
…(The authors of the "Copenhagen Diagnosis use the IPCC AR4 as a reference) you’d note that the IPCC’s smoothing methods do show plateauing of temperatures toward the end of the data, in 2005. Refer to Figures 3.1, Figure 3.4 Cell A, Figure 3.6, and FAQ3.1 Figure 1.
Figure 3 from the Copenhagen Diagnosis above, however, does not show the decreasing rate of rise. The above graph shows relatively straight lines over the past decade+. This leads me to believe that the smoothed curves are some type of polynomial trend lines. This is confirmed by the discussion of Figure 3 on page 13 of the “Copenhagen Diagnosis”:
“IPCC AR4 presented ‘an unambiguous picture of the ongoing warming of the climate system.’ The atmospheric warming trend continues to climb despite 2008 being cooler than 2007 (Figure 3). For example, the IPCC gave the 25-year trend as 0.177 +/- 0.052 deg C per decade for the period ending 2006 (based on the HadCRUT data). Updating this by including the last two years (2007 and 2008), the trend becomes 0.187 +/- 0.052 deg C per decade for the period ending 2008. The recent observed climate trend is thus one of ongoing warming, in line with IPCC predictions.
“Year-to-year differences in global average temperatures are unimportant in evaluating long-term climate TRENDS. During the warming observed over the 20th century, individual years lie above or below the long-term TREND line due to internal climate variability (like 1998); this is a normal and natural phenomenon. For example, in 2008 a La Niña occurred, a climate pattern which naturally causes a temporary dip in the average global temperature. At the same time, solar output was also at its lowest level of the satellite era, another temporary cooling influence. Without anthropogenic warming these two factors should have resulted in the 2008 temperature being among the coolest in the instrumental era, while in fact 2008 was the 9th warmest on record. This underpins the strong greenhouse warming that has occurred in the atmosphere over the past century. The most recent ten-year period is warmer than the previous ten-year period, and the longer-term warming TREND is clear and unambiguous (Figure 3).” [Caps are mine for emphasis.]
So if these are, in fact, trend lines, the authors of the “Copenhagen Diagnosis” have created a double-edged sword for themselves. Trend lines can be projected forward in time for use in forecasts. That is one of the intents of trend lines. (The trend line options for EXCEL provide the option for extending the trends.) So eyeballing the trend forecasts onto Figure 3, we see a continuous warming over the next decade or two, as the authors intended. http://i45.tinypic.com/2qiojgn.png
Figure 3 of the “The Copenhagen Diagnosis” With Forward Trend Projections
BUT (BIG BUT) those same trend lines can also be used for projections into the past, for hindcasts. Are they now reinstating the Medieval Warm Period? http://i48.tinypic.com/vpgbj4.png
Figure 3 of the “The Copenhagen Diagnosis” With Backward Trend Projections
And one last note: As quoted above, the authors of the “Copenhagen Diagnosis” stated, “the IPCC gave the 25-year trend as 0.177 +/- 0.052 deg C per decade for the period ending 2006 (based on the HadCRUT data).”
Actually, the IPCC lists that trend for the period ending in 2005, not 2006. Refer again to FAQ3.1 Figure 1 in AR4 Chapter 3. In the description, they write, “Linear trend fits to the last 25 (yellow), 50 (orange), 100 (purple) and 150 years (red) are shown, and correspond to 1981 to 2005, 1956 to 2005, 1906 to 2005, and 1856 to 2005, respectively.” The specific trend values are listed in the artwork.
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Global SST anomalies are still elevated, but they have not changed appreciably over the past few weeks. They are approximately 0.05 deg C lower than the peak earlier this year. http://i48.tinypic.com/n4ihj4.png
Global SST Anomalies
NINO3.4 SST anomalies for the week centered on November 18, 2009 also show little change over the past few weeks. They’re still in the moderate El Nino range, http://i47.tinypic.com/2n9m4ah.png
NINO3.4 SST Anomalies
####################
This is part 1 of a multipart post. It addresses critical comments about my earlier posts that dealt with the multiyear aftereffects of significant traditional El Nino events. Two specific El Nino events, those in 1986/87/88 and the 1997/98, caused Sea Surface Temperatures of the East Indian and West Pacific Oceans to remain at elevated levels during the subsequent La Nina events. These SST residuals, what I have called step changes in earlier posts for the sake of simplicity, bias the global SST during the La Nina events and give the impression of a gradual increase, one that is attributed to anthropogenic greenhouse gases.
This first post in the series is for those who wanted confirmation in scientific papers that El Nino events warm the oceans remote to the Pacific through processes other than heat transfer. In this post, I’ll use two papers as reference.
Wang (2005) describes how sea surface temperatures can and do rise in response to El Nino events in areas of the global oceans remote to the tropical Pacific. It concentrates on the Tropical North Atlantic and the Western Hemisphere Warm Pool. Basically, the rise in sea surface temperature of the North Atlantic is a response to changes in atmospheric circulation. Wang (2005) is provided here for those familiar with Hadley and Walker Circulation, wind stress and the like.
In the Abstract Wang (2005) writes, “The chapter also discusses a tropospheric bridge by the Walker/Hadley circulation that links the Pacific El Niño with warming of the tropical North Atlantic (TNA) and the WHWP.” For those who want the details, he provides the detailed discussion in subchapter 8 on page 22. His Summary and Discussion includes, “ENSO shifts the western Pacific heat source and atmospheric convective activity and then affects global atmospheric circulation. During El Nino, the equatorial Pacific Walker circulation is observed to be weakened. The anomalous meridional Hadley circulation in the eastern Pacific shows the air rising in the tropics, flowing poleward in the upper troposphere, sinking in the subtropics, and returning to the tropics in the lower troposphere. The anomalous Hadley circulation in the western Pacific is opposite to that in the eastern Pacific, indicating a weakening of the western Pacific Hadley circulation during El Nino. The NCAR/NCEP reanalysis field also shows that El Niño weakens the Atlantic Hadley circulation, consistent with an earlier result of Klein et al. (1999) that is inferred from correlation maps of satellite observations, and with the direct circulation analyses of Mestas-Nunez and Enfield (2001) and Wang (2002a). Wang (2002b, c) and Wang and Enfield (2003) suggest that following El Nino winters in which the Atlantic Hadley circulation is strongly weakened, the decreased subsidence over the subtropical North Atlantic results in the late winter weakening of the NE trades off Africa, the associated spring TNA warming (Enfield an Mayer 1997 and others), and the large summer warm pools (Wang and Enfield 2001).”
Again, Wang (2005) explains how El Nino events can and do raise SST in an area remote to the tropical Pacific. The response of the North Atlantic to ENSO can also be seen in a comparison graph of NINO3.4 SST anomalies and North Atlantic SST anomalies, Figure 1.
Note: The North Atlantic, of course, is also impacted by the AMO, which imposes an additional increase in SST anomalies over the term of the OI.v3 SST dataset. Refer to Figure 2. The impact of the AMO can be seen in a comparison graph of North Atlantic SST anomalies linear trends and the SST anomalies linear trends of the other ocean basins. This is discussed further in my post “Putting The Short-Term Trend Of North Atlantic SST Anomalies Into Perspective.”
TRENBERTH ET AL (2002)
The second paper is Trenberth et al (2002) "Evolution of El Nino–Southern Oscillation and global atmospheric surface temperatures." http://www.cgd.ucar.edu/cas/papers/2000JD000298.pdf
In it, Trenberth et al provide broader discussions of how ENSO events can and do impact global LST and SST. The paper deals with the period of 1950 to 1998, which obviously will not include the multiyear aftereffects of the 1997/98 El Nino that is evident in the data, but it does reinforce Wang (2005). It is an excellent reference for those interested in ENSO dynamics and global responses to ENSO.
In the abstract, Trenberth et al write, “However, most of the delayed warming outside of the tropical Pacific comes from persistent changes in atmospheric circulation forced from the tropical Pacific. A major part of the ocean heat loss to the atmosphere is through evaporation and thus is realized in the atmosphere as latent heating in precipitation, which drives teleconnections. Reduced precipitation and increased solar radiation in Australia, Southeast Asia, parts of Africa, and northern South America contribute to surface warming that peaks several months after the El Nino event. Teleconnections contribute to the extensive warming over Alaska and western Canada through a deeper Aleutian low and stronger southerly flow into these regions 0–12 months later.”
In other words, there are El Nino-induced processes other than heat transfer that cause warming outside of the tropical Pacific.
Back to the oceans: Trenberth et al go further under the heading of “3.3. Evolution of Spatial Patterns” to document the lag correlations between NINO3.4 SST anomalies and the SST anomalies of the Atlantic, Pacific, and Indian Oceans. In other words, they illustrate the length of time required for the major ocean basins to respond to the El Nino event. I have reproduced the Trenberth et al Figure 7 in this post as my Figure 3. They write, “Figure 7 shows a breakdown of Figure 3 by ocean sector for 1950–1978 and 1979–1998. It seems obvious that the lag of surface temperatures in the Pacific should be closely in phase with N3.4 because of the close proximity, and indeed this is the case, with a 2-month lag in both subperiods. However, the peak correlation is almost doubled in the earlier period. The Atlantic sector (defined as 90W–0) lags by 4–5 months, while the Indian Ocean sector (defined as 0–120E) shows a lag of 7 months for 1979–1998 but a skewed and smaller lag centered around +5 months from 1950 to 1978.” http://i35.tinypic.com/2mzfbbm.jpg
Figure 3
Throughout the rest of the paper they discuss the processes that cause the Atlantic, Pacific, and Indian Oceans to respond to El Nino events. These descriptions and discussions make up the body of the paper, so it’s not practical to reproduce all of it here.
With respect to heat transfer, in the Discussion Section, page 13, first subsection, Role of the Tropical Pacific Ocean, paragraph 37, Trenberth et al further describe, “The evolution of ENSO in the tropical Pacific Ocean illustrated here supports much of that previously described by Barnett et al. [1991], Zhang and Levitus [1996], Tourre and White [1995], Giese and Carton [1999], Smith [2000], and Meinen and McPhaden [2000] in the way that anomalies of subsurface ocean heat content in the western Pacific develop as they progress eastward across the equatorial Pacific, often with a dipole pattern across the Pacific, and then with anomalies progressing off the equator to higher latitudes. Zhang and Levitus [1996] found links only to the North Pacific, perhaps reflecting the available data, while our results reveal strong links to both hemispheres. The SST evolution lags somewhat behind that of the subsurface ocean and is damped by surface fluxes and transports out of the region by the atmosphere, emphasizing the dominant role of the surface wind stress and ocean dynamics and advection in producing the local ocean heat content and SST anomalies. This damping of the ocean signal, however, forces the atmospheric anomalies. Moreover, this aspect also emphasizes that in cold La Nina conditions the surface fluxes of heat are going into the ocean relative to the mean and are warming the ocean, although not locally as the heat is redistributed by currents.”
There are many more discussions of the diabatic and adiabatic processes throughout the paper. But El Nino events do cause SST anomalies outside of the tropical Pacific to rise. These can be seen in comparison graphs of NINO3.4 SST anomalies and the SST anomalies of the ocean basins, Figures 4 through 7. The North Atlantic comparison is shown above In Figure 1.
Through changes in atmospheric circulation and through the redistribution of warm water by ocean currents, El Nino events cause SST anomalies to rise.
The next post is the discussion of ENSO discharge/recharge. Trenberth et al provide an overview of this on page 16, paragraph 57, for those who want to read ahead. That post will also reinforce the processes that cause the SST anomalies of the East Indian and West Pacific to linger through the La Nina events and cause the bias that is mistaken for anthropogenic warming of the oceans.
Figure 1 is a copy of the most recent .gif animation of the equatorial Pacific temperature anomalies. It ends with the November 9, 2009 pentad. The magnitude of the subsurface anomalies (up to 6 deg C plus) have some bloggers concerned that the 2009/10 El Nino will reach super El Nino levels, comparable to the 1982/83 and 1997/98 El Nino events. This leads to an obvious question…
HOW DO THE CURRENT SUBSURFACE ANOMALIES COMPARE TO PAST EL NINO EVENTS?
I have not found an archive of the subsurface equatorial Pacific temperature graphics at the CPC website, but the European Centre for Medium-Range Weather Forecasts (ECMWF) website has the equatorial subsurface temperature anomaly cross-sections archived here: http://www.ecmwf.int/products/forecasts/d/charts/ocean/reanalysis/xzmaps/Monthly/
The graphics also include the Indian and Atlantic Ocean cross-sections. The archive starts in January 1959, and the most current month is October 2009. Unfortunately, it’s the recent elevated subsurface anomalies that concern some, and they rise significantly over the past few weeks, so the October monthly graphic really does not capture that recent surge. But ECMWF also presents daily “real time” views that start in February 2007. http://www.ecmwf.int/products/forecasts/d/charts/ocean/real_time/xzmaps/
So for this visual comparison of current conditions to past major El Nino events I’ll use the recent daily view and the historic monthly views.
To put the recent subsurface anomalies into perspective, here are .gif animations of the daily view for November 13, 2009 compared to the November graphics of major El Nino events since 1970. Again, keep in mind that these .gif animations compare monthly values for November to a daily value near to the middle of November 2009.
Also, this is only a visual comparison, nothing more. You'll also note that the monthly graphics of the earlier El Nino events appear to be more mature. That is, their warm anomalies reach as far east as the continental land mass, but the current warm anomalies are still a significant distance away. Is the current El Nino late to develop or is that difference in apparent development a function of the daily versus monthly views? Dunno.
The comparison of the current graphic to November 1997 (near the peak of the El Nino of the Century) is shown in Figure 3. The current anomalies are nowhere close to it. http://i35.tinypic.com/2hpmv83.gif
Figure 3
The SST anomalies of the 1982/83 El Nino peaked near to the NINO3.4 SST anomalies of the 1997/98 El Nino. The current subsurface anomalies appear lower than the November 1982 values, Figure 4. http://i35.tinypic.com/25rh5aw.gif
Figure 4
Third on the list of major El Nino events was the 1972/73 El Nino, and the current subsurface anomalies appear to fall short of its November 1972 values, as shown in Figure 5. http://i36.tinypic.com/2vabfk0.gif
Figure 5
The peak SST anomalies of the 1991/92 El Nino are next, and the current anomalies appear higher. Refer to Figure 6. http://i34.tinypic.com/2egafqt.gif
Figure 6
Next for your viewing pleasure is November 1986 (part way into the 1986/87/88 El Nino). The current values also appear a little stronger than it, too, Figure 7. http://i37.tinypic.com/15gp6w8.gif
Figure 7
THE BIG IF
So if these comparisons of subsurface anomalies can be used as a predictor of the peak SST anomalies, the current El Nino would peak somewhere between the 1991/92 El Nino and the 1972/73 El Nino. Will it? Dunno. I don’t make predictions. The current El Nino may have some surprises in store.
################## …And It Will Be Exploited By Those Who Fail To Understand The Reasons For The Rise
UPDATE (January 22, 2010): Corrected typo in paragraph after Figure 11. 1956 should have read 1856.
UPDATE (November 10, 2009): For those who prefer decades in terms of ordinal instead of cardinal year names, the only impact it has on this post is the average temperatures in Table 1: http://i35.tinypic.com/a26r80.jpg
Table 1 in that form may appear a bit premature, but with the El Nino this winter, I don’t believe the 2000s will be cooler than the 1990s.
The rest of the post is unaffected. There will be bloggers who, in the next few months, will jump all over the cardinal decade of 2000 to 2009 being warmer than 1990 to 1999. In fact, I’ve already seen evidence of it.
INITIAL NOTES
For some visitors to this blog, this post will be a merging and rehashing of a few of my earlier posts. But this post is different in a very important way. I have attempted to simplify the discussion of El Nino-caused step changes for those with less technical backgrounds.
The following narrated video “Visualizing El Nino” from the NASA/Goddard Space Flight Center Scientific Visualization Studio provides an excellent overview of the 1997/98 E; Nino, one of the El Nino events that created the aftereffects illustrated in this post.
I have provided links to the referenced studies and to the posts that provide more detailed explanations at the end of the following. They do not appear within the general discussion of this post.
Many of the illustrations in the following are .gif animations, with 5- to 10-second pauses between cells.
GLOBAL TEMPERATURES THIS DECADE WILL BE THE WARMEST ON RECORD
It became apparent a number of years ago that the current decade, the 2000s, would have the highest surface temperature since the start of the instrument temperature record. Prior to now, the record decade for Global Surface Temperature Anomalies, Global Lower Troposphere Temperature (TLT) Anomalies, and Global Sea Surface Temperature (SST) anomalies had been the 1990s. Table 1 shows the average 1990s and 2000s (to date) temperature anomalies furnished by different suppliers, and the difference between the two decades. And with the end of this decade drawing near, one should expect to hear of this new record time and time again. There are those who will exploit this in the next few months and in the years to come. Those parties will, of course, blame anthropogenic greenhouse gases for the rise. http://i38.tinypic.com/2ptz5gp.png
Table 1
THOSE WHO TRUMPET THE ELEVATED TEMPERATURES WILL FAIL TO ACKNOWLEDGE THE NON-LINEAR RELATIONSHIP BETWEEN THE EL NINO-SOUTHERN OSCILLATION (ENSO) AND GLOBAL TEMPERATURES
There have been a number of recent research papers that have illustrated a linear relationship between El Nino-Southern Oscillation (ENSO) and global temperature. These papers contradict what is clearly visible in the instrument temperature record, and that is, that the relationship between ENSO and global temperature is non-linear. In a comparison of global temperatures and natural variables, the researchers scale one of the ENSO indices, and after adjusting for other natural variables such as solar irradiance and volcanic aerosols, the researchers claim the difference between those natural variables and global temperatures must be caused by the increase in anthropogenic greenhouse gases. A simplified example of these comparisons is shown in Figure 1; it compares global SST anomalies and scaled NINO3.4 SST anomalies, one of the ENSO indices. It also shows their linear trends. I’ve excluded volcanic aerosol and solar adjustments to simplify the illustration. Note how the Global SST anomaly trend is increasing while the NINO3.4 SST anomaly trend is decreasing. As noted earlier, there are those who would like you to believe that the difference in those trends is caused by anthropogenic greenhouse gases. http://i34.tinypic.com/3589pj9.png
Figure 1
MULTIYEAR AFTEREFFECTS OF ENSO ARE VISIBLE AS STEP CHANGES IN THE SST RECORDS
The first dataset to be discussed is the sea surface temperature (SST) anomalies of the East Indian and West Pacific Oceans. This dataset represents approximately 25% of the global ocean surface area between 60S and 65N. A sizeable area, as can be seen in Figure 2. http://i34.tinypic.com/iwrz39.png
Figure 2
Figure 2 also shows the location of the NINO3.4 region of the equatorial Pacific. Its coordinates are 5S-5N, 170W-120W. Climate change researchers use this and other similar datasets when studying the magnitudes of El Nino and La Nina events and how often those events occur. Meteorologists also monitor NINO3.4 SST anomalies and other ENSO indexes to help them forecast the impacts of the current event on regional climate, hurricanes, etc. The SST anomalies of the NINO3.4 area of the Pacific correlate well with global temperature measurements. That is, when the SST anomalies of the NINO3.4 area rise during an El Nino event, global SST anomalies, and global TLT anomalies, and global surface temperature anomalies typically rise by lesser amounts. Researchers assume this relationship is constant, that it is linear, but as will be shown in the following, it is not linear. The global response to La Nina events is not the same as it is to El Nino events. This will be clearer as the discussion progresses.
Keep in mind that it is not only the SST anomalies of the NINO3.4 that rise and fall during El Nino and La Nina events. As can be seen in the video “Visualizing El Nino” above, the SST anomalies entire tropical Pacific are impacted.
Of the 9 official El Nino events since November 1981 (the start year of the SST dataset used to illustrate the effect), only two of these specific major traditional El Nino events occurred, one in 1986/87/88 and the other in 1997/98. See Figure 3, which is a .gif animation of the time-series graph of NINO3.4 SST anomalies. The other significant traditional El Nino in 1982/83 was counteracted by the volcanic eruption of El Chichon. http://i37.tinypic.com/2la6640.gif
Figure 3
Links to the individual cells of Figure 3:
Link to Figure 3 Cell A: http://i33.tinypic.com/9pw0no.png
Link to Figure 3 Cell B: http://i36.tinypic.com/apigjq.png
Link to Figure 3 Cell C: http://i35.tinypic.com/2yorexg.png
Something very curious happens in the East Indian and West Pacific area of the global oceans shown in Figure 2. The SST anomalies of the East Indian and West Pacific Oceans rise in steps in response to specific El Nino events. These particular El Nino events are major events that are traditional in nature, as opposed to El Nino Modoki (pseudo El Nino events), and they are also El Nino events that have not been impacted by explosive volcanic eruptions, such as El Chichon in 1982 and Mount Pinatubo in 1991.
Figure 4 is a .gif animation of two datasets presented in different ways. Cell A is a graph that compares the SST anomalies of the NINO3.4 region of the equatorial Pacific to the SST anomalies of the East Indian and West Pacific Oceans. The NINO3.4 SST anomalies have been scaled (multiplied by a factor of 0.2 in this case) so that the changes in them during the El Nino events of 1986/87/88 and 1997/98 are approximately the same magnitude as the responses in the East Indian and West Pacific Oceans. Note how the SST anomalies of the East Indian and West Pacific Oceans had little response to the 1982/83 El Nino. As discussed earlier, that El Nino was counteracted by the sunlight-blocking volcanic aerosols of the explosive eruption of El Chichon. Note also that there is a dip in the East Indian and West Pacific SST anomalies in 1991 and a rebound a few years later. That dip and rebound is caused by the eruption of Mount Pinatubo. In Cell B, linear trend lines have been added to the same datasets to show the relationship presented by researchers who assume the relationship between ENSO and global temperature is linear. The linear trends skew perspective and hide the actual cause of the rise in SST anomalies of the East Indian and West Pacific Oceans. In Cell C, I’ve included the average East Indian and West Pacific SST anomalies for the period before the 1986/76/88 El Nino, the period between the 1986/76/88 and 1997/98 El Nino events, and the period after the 1997/98 El Nino. These averages highlight the step changes that occurred in this portion of the global ocean. Again, these step changes are aftereffects of the 1986/87/88 and 1997/98 El Nino events. http://i37.tinypic.com/smrt44.gif
Figure 4
Links to the individual cells of Figure 4:
Link to Figure 4 Cell A: http://i33.tinypic.com/2cparf4.png
Link to Figure 4 Cell B: http://i38.tinypic.com/dz5go.png
Link to Figure 4 Cell C: http://i33.tinypic.com/14wu8pk.png
As you will note, the multiyear aftereffects aren’t true step changes. The SST anomalies for the East Indian and West Pacific Oceans don’t remain at the new higher temperatures indefinitely. They do, however, remain at higher levels (failing to respond fully to the La Nina) until the next series of lesser El Nino events drive the temperatures back up again, helping to maintain the higher levels. (The effects are easier to describe as step changes, which is why I refer to them that way.)
It is important to notice that the response of the East Indian and West Pacific Oceans to 1998/99/00 La Nina was not the same as the response to the El Nino that came before it. The SST anomalies for this area of the global oceans rose as would be expected in response to the El Nino, but it did not respond fully to the La Nina phase. Global SST response to La Nina events is not always the same as it is to El Nino events. And this difference between how Global SST responds to El Nino and La Nina events causes Global SST to rise.
These step changes in the East Indian and West Pacific Ocean SST anomalies are important for a number of reasons. First, the oceans represent approximately 70% of the surface area of the globe, and SST anomalies are included in the calculation of global surface temperature by GISS, Hadley Centre, and NCDC. Refer again to Table 1. In fact, the NCDC’s Optimum Interpolation SST dataset (OI.V2) used in Figure 4 has been included by the Goddard Institute for Space Studies (GISS) in their GISTEMP product since 1982. Second, these step changes are not reproduced by climate models. They also are not acknowledged by the scientific community--if they were, the papers listed at the end of this post would not illustrate a linear relationship between ENSO and global temperature. I have searched but have been unable to find any scientific paper that discusses these step changes. Third, the step changes bias the global SST anomalies upward and give the impression of a gradual increase in SST anomalies. This can be seen in a comparison graph of the SST anomalies of the East Indian and West Pacific Oceans, the SST anomalies of the “Rest of the World” (East Pacific, Atlantic, and West Indian Oceans), and the combination of the two, Figure 5. The period since 1996 is unique in the last 40+ years. There haven’t been any major volcanic eruptions to add noise to the data. This is why the data in Figure 5 starts in 1996. http://i38.tinypic.com/2ezjk9s.png
Figure 5 (Note: The time period listed in Figure 5 is wrong. The data in that graph does not start in November 1981. It runs from January 1996 to September 2009.)
Note how in Figure 5 the East Indian and West Pacific SST anomalies linger at the elevated levels while the SST anomalies for the “Rest of the World” are mimicking the variability of the NINO3.4 SST anomalies, shown in Figure 3. (That is, the SST anomalies for the “Rest of the World” are responding as researchers expect to both El Nino and La Nina events.) Over the next few years, ocean currents “mix” the elevated SST anomalies of the East Indian and West Pacific Oceans with the depressed SST anomalies of the “Rest of the World” oceans, dropping one and raising the other, until they intersect in 2003. This is more than 4 years after the end of the 1997/98 El Nino. Because the Global SST anomalies are a combination of the two, they are biased upward by the elevated East Indian-West Pacific SST anomalies and by the mixing with the waters of the “Rest of the World”. This gives the false impression of a gradual increase in global SST anomalies.
In other words, the effects of the major traditional El Nino events can linger for at least 4 years, causing gradual increases in global sea surface temperatures during that time. This gradual increase is incorrectly attributed to anthropogenic sources.
These effects are also discussed and illustrated in my video “The Lingering Effects of the 1997/98 El Nino”.
MULTIYEAR AFTEREFFECTS OF ENSO ARE ALSO VISIBLE AS STEP CHANGES IN THE TLT RECORDS
Since 1979, two groups have analyzed the satellite-based Microwave Sounding Unit (MSU) radiometer data to determine atmospheric temperatures at different levels. These groups are Remote Sensing Systems (RSS) and the University of Alabama in Huntsville (UAH). We’ll be using the data from RSS in this discussion. One dataset, the Lower Troposphere Temperature (TLT) anomalies, correlate well with the global surface temperature anomalies determined from direct land and sea surface temperature observations.
Lower Troposphere Temperature (TLT) anomalies also show upward step changes in response to the significant traditional 1986/87/88 and 1997/98 El Nino events. And similar to the discussion of sea surface temperatures above, only a portion of the global TLT anomalies show clear signs of these upward steps. In this case, it’s the latitude band of 20N to 82.5N or the Mid-To-High Latitudes of the Northern Hemisphere. Refer to Figure 6 for the area of the globe included within these latitudes. It represents in the neighborhood of 33% of the global surface area. http://i34.tinypic.com/id7h4k.png
Figure 6
The graph in Figure 7 compares the NINO3.4 SST anomalies to the Lower Troposphere Temperature (TLT) anomalies of the Mid-To-High Latitudes of the Northern Hemisphere. The scaled NINO3.4 SST anomalies are used again as a reference for the timing and magnitude of significant traditional El Nino events. As you can see, the TLT anomaly data for this area of the globe is noisy, but it is obvious that the TLT anomalies rose since 1979, a rise that is normally attributed to manmade greenhouse gases. http://i35.tinypic.com/2coiln8.png
Figure 7
A common technique used to reduce data noise is to smooth it by calculating the average of a number of months before and after a given month, and to calculate this average for each month for the entire length of the dataset. (The same technique was used in Figure 5.) The TLT anomaly data in Figure 8 has been smoothed with a 13-month running average filter. Note how, when compare to Figure 7, there is much less noise in the smoothed data. Figure 8 is another .gif animation. It illustrates the TLT anomaly data for the Mid-To-High Latitudes of the Northern Hemisphere and the scaled NINO3.4 SST anomalies from different points of view. Cell A illustrates the data without any comments. Depending on your perspective, you can see a gradual rise in the TLT anomaly dataset that’s disrupted by ENSO events and volcanic eruptions or you can see three periods of relatively flat TLT anomalies that are punctuated by ENSO and volcanic eruptions with two major step increases caused by the 1986/87/88 and 1997/98 El Nino events. In Cell B, the impacts of the two major volcanic eruptions are noted. These are the 1982 eruption of EL Chichon and the Mount Pinatubo eruption in 1991. As with the SST data, the El Chichon eruption counteracted the impact of the 1982/83 El Nino. But the lesser El Nino in 1991/92 was no match for the Mount Pinatubo eruption, and TLT anomalies made a substantial drop. The TLT anomalies rebounded a few years later as the volcanic aerosols in the stratosphere dissipated. Cell C shows the positive linear trend of the TLT anomalies for the Mid-To-High Latitudes of the Northern Hemisphere and it shows the negative trend in the SST anomalies of the NINO3.4 region of the equatorial Pacific. The difference between the two, as discussed earlier, is attributed by researchers to anthropogenic greenhouse gases. However, the attribution is unfounded when the global data is broken down into smaller subsets. The heat released by significant El Nino events can and do cause step changes in the TLT anomalies of the Mid-To-High Latitudes of the Northern Hemisphere. This is clearly visible when the average temperatures before and after those significant El Nino events are displayed on the graph, Cell D. http://i35.tinypic.com/j0f89k.gif
Figure 8
Links to the individual cells of Figure 8:
Link to Figure 8 Cell A: http://i37.tinypic.com/30rraky.png
Link to Figure 8 Cell B: http://i37.tinypic.com/2yjocr9.png
Link to Figure 8 Cell C: http://i38.tinypic.com/2jcdc13.png
Link to Figure 8 Cell D: http://i37.tinypic.com/2ue1jz8.png
It is primarily those two shifts in the Mid-To-High Latitude TLT Anomalies of the Northern Hemisphere that cause the upward trend in Global TLT Anomalies.
DO ANTHROPOGENIC GREENHOUSE GASES FUEL EL NINO EVENTS?
The source of heat for El Nino events is the Tropical Pacific, and there is no evidence that greenhouse gases have a significant effect on the Ocean Heat Content (OHC) anomalies of the Tropical Pacific. Refer to Figure 9. It is also a .gif animation. Cell A shows the comparison graph of Tropical Pacific OHC, scaled NINO3.4 SST anomalies, and scaled Sato Index of Stratospheric Aerosol Optical Thickness. The Sato Index data is presented to illustrate the timing of explosive volcanic eruptions. Like the other comparisons in this post, the NINO3.4 SST anomalies are used to illustrate the timing and magnitude of El Nino and La Nina events. The OHC dataset was created by the National Oceanographic Data Center (NODC). It presents OHC to depths of 700 meters. This OHC data was introduced with the Levitus et al (2009) paper “Global Ocean Heat Content 1955-2008 in light of recently revealed instrumentation problems”. Cell B highlights the two decade-long declines in Tropical Pacific OHC. Cell C calls attention to the upward surges (steps) in Tropical Pacific OHC that occurred during the multiyear La Nina events that followed the 1972/73 and 1997/98 El Nino events. And Cell D highlights a curious rise in Tropical Pacific OHC that occurred in the few years leading up to the 1997/98 El Nino. I have searched for but have not found any scientific paper that discusses this sudden surge that fueled the 1997/98 El Nino. http://i36.tinypic.com/dpzu6h.gif
Figure 9
Links to the individual cells of Figure 9:
Link to Figure 9 Cell A: http://i33.tinypic.com/2gwys1t.png
Link to Figure 9 Cell B: http://i37.tinypic.com/kamom.png
Link to Figure 9 Cell C: http://i35.tinypic.com/w075g6.png
Link to Figure 9 Cell D: http://i34.tinypic.com/10e28ic.png
An additional note about Figure 9: Note how the OHC dips during the El Nino events and rebounds during the La Nina events. The El Nino discharges heat from the Tropical Pacific, and the La Nina recharges the heat. This is accomplished by variations in total cloud amount. If the La Nina is not being impacted by volcanic aerosols and if the La Nina lasts for more than one year, ocean heat content rises above its previous level, creating the upward step.
The changes in Tropical Cloud Amount Percentage mimic NINO3.4 SST anomalies. Refer to Figure 10. That is, when NINO3.4 SST anomalies rise, Tropical Pacific Cloud Amount increases, and when NINO3.4 SST anomalies drop during the La Nina phase, Tropical Pacific Cloud Amount decreases. Less cloud cover means more downward shortwave radiation (visible sunlight) is able to warm the Tropical Pacific. In Cell C of Figure 10, the sudden drop in Tropical Pacific Cloud Amount in 1995 is highlighted. As noted above, it appears this decline in cloud amount fueled the 1997/98 El Nino. http://i37.tinypic.com/24wztqe.gif
Figure 10
Links to the individual cells of Figure 10:
Link to Figure 10 Cell A: http://i35.tinypic.com/4rxele.jpg
Link to Figure 10 Cell B: http://i36.tinypic.com/2z4d6hc.jpg
Link to Figure 10 Cell C: http://i36.tinypic.com/34obno7.jpg
NATURAL VARIATIONS IN THE NORTH ATLANTIC SST ALSO CONTRIBUTED TO THE DIFFERENCE IN GLOBAL TEMPERATURE BETWEEN THE 1990s AND THE 2000s
The SST anomalies of the North Atlantic Ocean are also impacted by another natural variable, the Atlantic Multidecadal Oscillation or AMO. The AMO is a semi-periodic variation (50 to 80 years) in the SST anomalies of the North Atlantic that has its basis in Thermohaline Circulation (THC) or Atlantic Meridional Overturning Circulation (AMOC). These variations are visible in the reconstruction of North Atlantic SST from 1567 to 1990, Figure 11. This dataset was created by Gray et al (2004) “Atlantic Multidecadal Oscillation (AMO) Index Reconstruction”. (IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2004-062. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.) http://i36.tinypic.com/wld5kl.jpg
Figure 11
For the period of the instrument temperature record, the AMO is presented as detrended North Atlantic SST anomalies. Refer to Figure 12, which is also a .gif animation. Cell A of Figure 12 illustrates the AMO data calculated by the NOAA Earth System Research Laboratory (ESRL) from January 1856 to March 2009. The data has been smoothed with a 37-month filter to remove the noise. Cell B notes that the AMO is a naturally occurring variation in the SST anomalies of the North Atlantic. And Cell C illustrates the average AMO SST values for the 1990s and the 2000s. The difference between these two averages represents the contribution of the AMO to the rise in North Atlantic SST Anomalies from the 1990s to the 2000s. Keep in mind that, while the North Atlantic covers only a surface area that is approximately 15% of the global oceans, the AMO is also known to also impact the surface temperatures of Europe and North America and the SST of the Eastern Tropical Pacific. http://i38.tinypic.com/oj4bqg.gif
Figure 12
Links to the individual cells of Figure 12:
Link to Figure 12 Cell A: http://i37.tinypic.com/mwqeqh.jpg
Link to Figure 12 Cell B: http://i34.tinypic.com/kaqtjq.jpg
Link to Figure 12 Cell C: http://i35.tinypic.com/2gtddn7.jpg
CLOSING
There is little doubt that the decade of the 2000s will have higher land surface, sea surface, and lower troposphere temperature anomalies than the 1990s. There will be those who will wrongly attribute the rise from decade to decade to anthropogenic greenhouse gases, when it is very apparent that the actual cause is the lingering effects of the 1997/98 El Nino event. Attempts will be made to contradict the obvious by those who fail to acknowledge or comprehend the multiyear aftereffects of significant traditional El Nino events. They will present numerous unfounded arguments. Here are a few that have been tried.
Argument 1: The short-term global warming of El Nino events are countered by the short-term global cooling of the La Nina events that follow them.
What The Instrument Temperature Record Shows: That’s true for only parts of the globe and for some El Nino events. It is not true, however, for the SST anomalies of the East Indian and West Pacific Oceans and for the TLT anomalies of the Mid-To-High Latitudes of the Northern Hemisphere. Refer to Figures 4 and 8. The effects of the 1986/87/88 and the 1997/98 El Nino lingered through the La Nina events that followed them in those datasets. This created the appearance of gradual rises in global SST and TLT anomalies.
Argument 2: Global warming caused by anthropogenic greenhouse gases is responsible for the increase in the number of major El Nino events since 1975. (This argument is normally made by someone referring to an ENSO Index that starts in 1950.)
What The Instrument Temperature Record Shows: There are multidecadal variations in the frequency and magnitude of ENSO events. This can be seen by smoothing the NINO3.4 SST anomalies from 1870 to 2009 with a 121-month filter. Refer to Figure 13. During epochs when the frequency and magnitude of El Nino events outweigh the frequency and magnitude of La Nina events, global temperatures rise. And during epochs when the frequency and magnitude of La Nina events outweigh the frequency and magnitude of El Nino events, global temperatures drop. http://i43.tinypic.com/33agh3c.jpg
Figure 13
Argument 3: El Nino events don’t create heat.
What The Instrument Temperature Record Shows: During El Nino events, warm water that had been stored below the surface of the western tropical Pacific (in the Pacific Warm Pool) sloshes to the east and rises to the surface. Tropical Pacific SST anomalies increase in response. In this way, more heat than normal is released from the tropical Pacific to the atmosphere. But El Nino events not only release heat into the atmosphere, they also shift atmospheric circulation patterns (Hadley and Walker Circulation, surface winds, cloud cover). These shifts in the circulation patterns and cloud cover cause surface temperatures and OHC outside of the tropical Pacific to rise.
It is important to note that the vast majority of the warm water that sloshes east during the El Nino had been stored below the surface before the El Nino. While below the surface (to depths of 300 meters) it was not included in the instrument temperature record. But during the El Nino, that warm water has been relocated to the surface and is included in the surface temperature record. So, El Nino events relocate warm water from an area that was not included in the calculation of global temperature to the surface where it is included.
Argument 4: Climate models used by the IPCC reproduce these El Nino-induced step changes.
What The Climate Models Show: Most of the climate models (GCMs) used by the IPCC in AR4 for hindcasting 20th Century climate do not bother to model ENSO. Those that make the effort do not model it well. The frequency, magnitudes, linear trends, and multiyear aftereffects of those models do not match the surface temperature record. The step changes that exist in the instrument temperature record, which are the bases for the much of the rises in global temperatures, do not exist in the model outputs of the 20th century.
If and when GCMs can reproduce the past frequency and magnitude of ENSO events, if and when GCMs can reproduce the multiyear aftereffects of ENSO events, which are these El Nino-induced step changes (including the ones that also appear in the OHC records), then GCMs may have some predictive value. At present they cannot reproduce ENSO or its multiyear aftereffects. At present they have no value.
This failure of GCMs to properly account for the multiyear impacts of major El Nino events (and other natural variables such as the North Atlantic Oscillation) can be seen in a graph of the actual rise in global OHC versus the projected rise forecast by GISS, Figure 14. The GCM used by GISS based its projection on the rise in Ocean Heat Content during the 1990s, assuming the trend would continue at that pace. But during the 1990s, the vast majority of the rise in OHC was caused by the combined effects of ENSO and the North Atlantic Oscillation, and these are natural variables that the GISS GCM did not model. Since 2003, Global Ocean Heat Content has been relatively flat, while the GISS projection reaches to unrealized levels. http://i37.tinypic.com/i6xtnl.png
Figure 14
PAPERS THAT PORTRAY A LINEAR RELATIONSHIP BETWEEN ENSO AND GLOBAL TEMPERATURES
In a good portion of this post, I’ve illustrated that the relationship between ENSO and global temperatures is not linear. The following is a list of papers that portray a linear relationship even though the instrument temperature record indicates otherwise. There are likely more of them in existence, and there will likely be more of them in the future.
Comments that are political in nature or that have nothing to do with the post will be deleted. #### The Smith and Reynolds SST Posts DOES NOT LIST ALL SST POSTS. I stopped using ERSST.v2 data for SST when NOAA deleted it from NOMADS early in 2009.
Please use the search feature in the upper left-hand corner of the page for posts on specific subjects. #### NOTE: I’ve discovered that some of the links to older posts provide blank pages. While it’s possible to access that post by scrolling through the history, that’s time consuming. There’s a quick fix for the problem, so if you run into an absent post, please advise me. Thanks. #### If you use the graphs, please cite or link to the address of the blog post or this website.
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