El Niño Residuals Cause the C-Shaped Warming Pattern in the Pacific

In the recent model-data comparison of satellite-era sea surface temperature anomalies—appropriately titled Maybe the IPCC’s Modelers Should Try to Simulate Earth’s Oceans—we compared trend maps of modeled and observed sea surface temperature anomalies from 1982 to 2013. See Figure 1. The models showed a general warming of the Pacific with the highest warming rates in the tropics and in the northwest North Pacific. In the real world, the data showed a C-shaped warming pattern, with extensive warming along the Kuroshio-Oyashio Extension east of Japan and along the South Pacific Convergence Zone (SPCZ) east of Australia and New Zealand, and with little to no warming in the tropics or the Eastern Pacific. It has come to my attention that some persons believe the start and end dates are responsible for the C-shaped pattern; that is, they think the C-shaped pattern appears in the data trend map because the Reynolds OI.v2 sea surface temperature data start in an El Niño development year and end with an ENSO-neutral year (which was preceded by back-to-back La Niña events). Their assumption is wrong, of course. The warming pattern does not depend on the start and end years I’ve used for the trend maps. The warming pattern is caused by what Kevin Trenberth and others called “ENSO residual” effects in their 2002 paper The Evolution of El Niño and Global Atmospheric Surface Temperatures. It might be easier to think of El Niño residuals as leftovers from strong El Niño events.

Fig 1 - Trend Map Comparison

Figure 1


First, let’s confirm that the C-shaped warming pattern in the Pacific does not depend on the 1982 (El Niño development) start year and 2013 (ENSO-neutral) end year. And to do that we’ll reverse the extremes; that is, we’ll start in a year with La Niña conditions and end with El Niño. According to NOAA’s Oceanic NINO Index (ONI), 1984 began and ended in “official” La Niña conditions. Both trend maps in Figure 2 start in 1984. The 2009/10 El Niño evolved in 2009 and decayed in 2010, so I’ve presented trend maps with both 2009 and 2010 as end years: 2009 on the left and 2010 on the right. The C-shaped pattern appears in both maps. As noted earlier, starting the trend maps during an El Niño year and ending them during an ENSO-neutral year, used in the earlier post, did not cause the C-shaped spatial warming pattern in the Pacific Ocean. That pattern also exists if we start the trend map during a La Niña and end during an El Niño.

Fig 2 - Data Trend Map Comparison

Figure 2

That C-shaped warming pattern of the Pacific sea surfaces exists even if we start the trend analysis as far back as 1977. See Figure 3. That is the first year after the 1976 Climate Shift, which, as you’ll recall, raised the sea surface temperature anomalies of the East Pacific Ocean almost 0.2 deg C. I’ve presented trends from 2 sea surface temperature reconstructions for the period of 1977 to 2013 in Figure 3, NOAA’s ERSST.v3b on the left and UKMO’s HADISST on the right.

Fig 3 - Data Trend Map Comparison 1977-2013

Figure 3


We’ll return to the satellite-enhanced Reynolds OI.v2 sea surface temperature data for this part of the discussion. Figure 4 presents the sea surface temperature anomalies of the West Pacific Ocean. I’ve added a few notes to it. Since November 1981, the sea surface temperatures there warmed in two steps. The first step was in response to the 1986/87/88 El Niño and the second step was a response to the 1997/98 El Niño. After the 1997/98 El Niño, there was little to no longer-term warming there, just some year to year variations caused by the subsequent and lesser El Niño and La Niña events. Additionally, between the 1986/87/88 and 1997/98 El Niños, the sea surface temperature data for the West Pacific also show no warming. The big dip and rebound starting in 1991 is a response of the sea surface temperatures of the West Pacific Oceans to the eruption of Mount Pinatubo.

Figure 4

Figure 4

Kevin Trenberth of NCAR, who is known for his El Niño research, referred to these upward shifts in temperature as “big jumps” in his article for Royal Meteorological Society titled Has Global Warming Stalled? back in May 2013. (We discussed that article in the post Open Letter to the Royal Meteorological Society Regarding Dr. Trenberth’s Article “Has Global Warming Stalled?”.) Since then, Trenberth has confirmed strong El Niño events are responsible for the “big jumps”. Trenberth discussed the “big jumps” in his August 2013 interview on NPR . “1998” is a reference to the 1997/98 El Niño, of course (my boldface):

The oceans can at times soak up a lot of heat. Some goes into the deep oceans where it can stay for centuries. But heat absorbed closer to the surface can easily flow back into the air. That happened in 1998, which made it one of the hottest years on record.

Trenberth says since then, the ocean has mostly been back in one of its soaking-up modes.

“They probably can’t go on much for much longer than maybe 20 years, and what happens at the end of these hiatus periods, is suddenly there’s a big jump [in temperature] up to a whole new level and you never go back to that previous level again,” he says.

You can think of it like a staircase. Temperature is flat when a natural cool spell cancels out the gradual temperature increase caused by human activity. But when there’s a natural warm spell on top of the long-term warming trend, the story is dramatically different.

Kevin Trenberth is obviously still trying to keep alive the notion that greenhouse gases are responsible for the warming of the global oceans.

In Figure 5, I’ve added an arbitrarily scaled ENSO index to the graph (dotted purple curves) to confirm the timing of the upward steps. NINO3.4 sea surface temperature anomalies are a commonly used index for the timing, strength and duration of El Niño and La Niña events.

Figure 5

Figure 5

And in Figure 6, I’ve compared the West Pacific data to the sea surface temperature anomalies of two other subsets of the global oceans. The East Indian-West Pacific data was the first subset of the global oceans where I reported on the upward steps. That was more than 5 years ago. See the posts “Can El Niño Events Explain all of the Global Warming Since 1976?” Part 1 and Part 2. (The WattsUpWithThat cross posts are here and here for those who want to review the comments.) I later expanded the region where the sea surface temperature data show the upward shifts to include the South Atlantic, Indian and West Pacific Oceans, which is also shown in Figure 6. (See the map here for the location and scale of that subset.) The South Atlantic, Indian and West Pacific subset covers more than 50% of the surface of the global oceans. All three subsets of the global oceans show the same basic El Niño-caused upward shifts, and that makes sense since they share common data.

Figure 6

Figure 6


The following is a very brief description of how the upward steps are created. An El Niño event releases a colossal volume of warm water from the surface and, more importantly, from below the surface of the western tropical Pacific and spreads that warm water across the surface of the eastern tropical Pacific. In the cases of the 1997/98 El Niño and the 1987/88 portion of the 1986/87/88 El Niño, that warm water spread east as far as the west coast of the Americas. The El Niño does not “consume” all of the warm water that had traveled east, so after the El Niño peaks and the trades winds resume, the trade winds push the leftover warm surface water back to the West Pacific. And there is another phenomenon called a slow-moving Rossby wave that returns the leftover subsurface warm waters to the West Pacific. Ocean currents carry all of the leftover warm water poleward creating the C-shaped warming pattern in the Pacific…and into the Indian Ocean.

In the animation of sea level anomalies here (Animation 3-1 for my ebook Who Turned on the Heat?), an example of a slow moving Rossby Wave can be seen carrying leftover subsurface warm water, from east to west, at about 10N, following the 1997/98 El Niño.

Simply put, before the El Niño there was a huge amount of warm water stored below surface of the western tropical Pacific. While it was below the surface, it was excluded from the surface temperature record. During and after the El Niño, that warm water is now on the surface, raising the sea surface temperature of the global oceans (and raising land surface air temperatures in response). On the threads of blog posts over the years, the upward steps have been described by some persons as a ratcheting effect.


I created and collected a number of animations of the 1997/98 El Niño and its aftereffects for my ebook Who Turned on the Heat?. They are linked to and discussed in the blog post Animations Discussed in “Who Turned on the Heat?”.

Animation 6.1 presents a series of sea surface temperature anomaly maps before, during and after the 1997/98 El Niño. I’ve used maps of 12-month average sea surface temperature anomalies to minimize weather noise and the seasonal cycle in the data. Also included in the animation is a comparison graph that infills as the animation progresses. One of the datasets is a scaled ENSO index (NINO3.4 sea surface temperature anomalies) to show the timing of the 1997/98 El Niño and the trailing 1998-01 La Niña. The other dataset in the graph is the sea surface temperature anomalies of the East Indian and West Pacific Oceans. Also see Figure 6 above. So you can watch the upward shift take place in the East Indian and West Pacific data and also watch the C-shaped warming pattern form.


If the subject of long-term aftereffects of El Niño events is new to you, refer to the illustrated essay The Manmade Global Warming Challenge (42MB). It includes additional discussions of the upward shifts (the Trenberth “big jumps”) in sea surface temperatures.

In 2012, I published my e-book about the phenomena called El Niño and La Niña. It’s titled Who Turned on the Heat? with the subtitle The Unsuspected Global Warming Culprit, El Niño Southern Oscillation. It is intended for persons (with or without technical backgrounds) interested in learning about El Niño and La Niña processes and in understanding the natural causes of the warming of our global oceans for the past 30 years. It presents how the sea surface temperature data and ocean heat content data account for their warming—and there are no indications the warming was caused by manmade greenhouse gases. None at all.

Who Turned on the Heat? was introduced in the blog post Everything You Ever Wanted to Know about El Niño and La Niña……Well Just about Everything. The Free Preview includes the Table of Contents; the Introduction; the beginning of Section 1, with the cartoon-like illustrations; the discussion About the Cover; and the Closing.

Please buy a copy. (Paypal or Credit/Debit Card). You do not need to have a PayPal account. Simply scroll down to the “Don’t Have a PayPal Account” purchase option. It’s now sale priced at US$5.00.


The satellite-enhanced Reynolds OI.v2 sea surface temperature anomaly data used in this post is available through the NOAA NOMADS website. The trend maps were created at, and the ERSST.v3b and HADISST sea surface temperature data, are available through the KNMI Climate Explorer.


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Layman question: IF the middle of the oceans warmed up a tenth of a degree or so, admittedly a lot of energy, just how does that energy become focused to warm the atmosphere above by several whole degrees?

David L.

Richard111 on April 6, 2014 at 4:51 am
Layman question: IF the middle of the oceans warmed up a tenth of a degree or so, admittedly a lot of energy, just how does that energy become focused to warm the atmosphere above by several whole degrees?
By a process know as “Maxwell’s demon”
Is a course in thermodynamics required as part of the climatology curriculum?

Ron Clutz

Thanks again Bob for your clear explanations. I am struck by your Figure 5, showing such a negative correlation between the West Pacific and Nino3.4. Do I understand correctly that while La Ninas are on in Nino3.4, the SSTs throughout West Pacific are rising (+anomalies) and vice-versa for El Ninos?

Ron Clutz

Oh,I also meant to ask you Bob about your perspective on the outlook for El Nino in 2014.

Whilst accepting Bob’s description of the immediate cause for a step upwards I think one should go further if there are multiple successive such upward steps over decades or centuries.
I suggest that the reason for such long term stepping patterns, whether upward or downward, is changing solar activity levels altering global cloudiness so as to change the amount of solar energy entering the oceans.
That skews the balance between El Nino and La Nina dominance over time.
Thus, there has most likely been such upward stepping periodically since the LIA and most likely there was downward stepping from the MWP to the LIA.
Upward steps would occur from one positive phase of the Pacific Multi-decadal Oscillation during a time of increasing solar activity and from one negative phase to the next during a time of decreasing solar activity.
That proposition forms part of my New Climate Model.


C shaped warming? Are we doomed yet?

David L. says:
April 6, 2014 at 4:55 am
By a process know as “Maxwell’s demon”
ah, we make zee joke, no?


C-shaped? – something like the configuration of a Zulu army in attack mode …

James Strom

So the ENSO process is like a staircase. The earth has been around in its current configuration, or something close, for millions of years. If only upward traffic is allowed on the staircase, we would be pretty hot by now. But we’re not, so there must be operating modes of ENSO that we haven’t observed as yet.

Thanks, Bob. Good explanation.
You have shed bright light on ENSO, the most notable natural phenomenon going on the Pacific and Indian Oceans that affects the whole planet.
So much more is yet to be discovered abut the way the Sun’s energy enters the Earth climate system.


You have shown in past articles that the Pacific Ocean, pole to pole has a 30-35 year cycle . Surely a short term El Nino will have a different impact and development pattern if it occurs when the Pacific ocean is in the cooling mode than when it is in the warming mode and even different when it is in the transition mode from one to the other . Hence there tends to be more frequent and stronger El Ninos during the Ocean warming modes [1970-2000) and why El Ninos do not lower global atmosphere temperatures significantly during ocean cooling modes [ like 1895-1910]. Any comment?

Sweet Old Bob

RoHa at 6:27 am
When it becomes Pac Man….


The C-shaped warming pattern found in the observed data corresponds to the pattern of tectonic plates. See http://hisz.rsoe.hu/alertmap/index2.php for maps of the world that shows the plate boundaries and can be zoomed down to see the ocean floor. As the days go by, you’ll see icons denoting volcanic activity, earthquakes, and various other phenomena (the website is actually designed to show all kinds of disasters, natural and man-made) over the entire map. I propose that the C-shaped warming pattern is due to lava eruptions and mild volcanic activity. Such natural actions would make the water extremely hot in the immediate vicinity of the lava. As the heat travels toward the surface, the water temperature gradually warms up compared to ambient, the plume of heat cools down, and the formerly hot water is dispersed over a very wide area due to ocean currents and atmospheric winds. It seems reasonable to me that by the time the plume has reached the sea surface, the water over a very wide area could become warmer by 0.2 degrees C. Also remember that lava eruptions and mild volcanic activity each occur in a very small vicinity, but that many such spots occur over the course of a short time period (e.g., a day) and could therefore cause a gradual warming at the sea surface.


Again, this falls in the not-even-wrong category.
Your “residuals” is a direct result of more solar input to most of the tropics except eastern Pacific during El-Ninos.

a p

There are too many variables and too many unknowns for computer models didn’t you read about this problem?


You know Bob that if you have a sin pattern (wave like) and superimpose it on a positive rise over time, it would look like a series of steps.


We have discussed your flawed “theory” about La-Ninas warming the ocean several times.

Arno Arrak

Bob, I have no idea where your temperature data come from but they have no relation to reality. Get yourself some decent UAH and RSS satellite data and dump this junk you are using. There is no such thing as a step rise in the eighties and nineties. There is a step rise right after the super El Nino that raises global temperature by a third of a degree in only three years and then stops. That is why all twenty-first century temperatures are higher than twentieth, not because of ongoing warming as Hansen tries to sell you. There are five El Nino peaks in the eighties and nineties with slight random variations whose centers of gravity line up in a horizontal straight line from 1979 to early 1997. This defines the temperature trend, not your imagined boxes. The super El Nino is twice as high as these El,Ninos are but in your data you do not even notice its existence. It gets worse in the twenty-first century where the beginning of the high at 2002 is exaggerated but the La Nina of 2008 and the El Nino of 2010 have been demoted to unidentifiable squiggles. Plus, that so called “impact of eruption of Mount Pinatubo” is nothing more exotic than an ordinary La Nina. I suggest you give up using that 13 month filter and start using a transparent magic marker instead. Or Photoshop layers. Eruptions of stratovolcanoes do not cause volcanic cooling in the troposphere: their hot gases go straight into the stratosphere. Cooling follows in about two years after the eruption but it stays up there and never reaches ground level. I suggest you educate yourself in these matters. Its easy: just read my book with comprehension.


… and yes, it takes a while for the absorbed solar input to reach the surface so yes, it is out of phase and should be.

Matt Souders

Bob, this may be a stupid question…but if the climate were in an equilibrium state, what would the force be that drives the ocean back to a neutral temperature? In other words…why doesn’t the El Nino ratchet cause the ocean to spiral off into ever increasing levels of warmth?
It seems that Trenberth thinks you are correct about the ratchet effect on temperature…but thinks the general warming of the global oceans that leads to the increasing warmth of those subsurface warm waters that fuel an El Nino warming period is caused by AGW. What is your counter-argument to this theory?

Joel O'Bryan

two considerations of immense import are missing in Bob’s discussion of his analysis.
1) the importance of water vapor in the lower troposphere that feeds convection and thus vapoor into the stratosphere. (water vapor is the most potent GHG). A further figure on down-welling IR with fig 5 might provide the right segue into that meld. These individual phenomenon working in concert provide feedback may allow the emergent property of climate control to operate (homeostasis in the presence of perturbations).
2) the period 1960- 2002 is a period of steadily increasing solar maximums. The Earth’s climate and ocean systems are integrating that rising input during the analyzed 1980-2010 period here by Bob in the ENSO and SST data. We are now possibly on a downward solar activity that may lead to a Grand Minimum lasting 50-200+ years. 50 years from now a heat releasing super El Nino may be a creature of distant history. But even if we see a major cooldown by 2050, I’m confident homeostasis maintaining processes will adapt.

george e. conant

I have a question, these el nino and la nina events do have a known cycle through the centuries, and those big step ups can’t possibly be the only direction otherwise we would have boiling oceans long ago. The question is do we have records of big step downs ?


Are you you saying that deep ocean currents have no effect on ocean surface temperatures ?. Suggest you read material of Prof Wm Gray as well. Just look at the period from 1870-1910 . when ocean temperatures dropped despite the many El Ninos.

Greg Goodman

It’s interesting to compare figure 4 to this graph of the effect of the two major eruptions on the stratosphere. This initial effect is a warming ( aerosols blocking incoming solar causing a warming of the stratosphere). Once the aerosols have mostly been washed out the stratosphere taken on a set drop in temperature. In each case almost exactly 0.5K cooler than the level before the eruption.
It seems that the stratosphere gets ‘cleaned’ of something ( probably mainly ozone ) that leaves it more transparent and trapping less solar. The implication being that more energy makes it to the lower atmosphere.
If we look at figure 4 it seems that , though less clearly defined due to other variability, there is a surface warming that mirrors the stratospheric cooling.
The clichéd explanation is that volcanoes cause cooling but the evidence, beyond the two or three years of the initial impact, points to the opposite effect . It is clear that at least in the stratosphere there is a durable long term offset that is clearly attributable to the eruptions.
It looks like about 0.1K increase each time in SST.
It would seem unlikely that there is not a corresponding effect in the lower atmosphere, unless the climate system has very strong negative feedbacks that render it totally immune to changes in radiative forcing. Even a notable negative feedback would require some rise in temperature to drive the feedback response.
But that can’t be happening because, as we all know, the climate feedbacks are net positive and multiply any changes by a factor of about three. Don’t they??

Greg Goodman

lgl says: … and yes, it takes a while for the absorbed solar input to reach the surface so yes, it is out of phase and should be.
Like this you mean?


There’s an article on HockeySchtick that claims that El Niño’s are set off at the beginning of solar cycles. Always a skeptic, I plotted recent data and took a look. Sure enough, at the beginning of Cycles 23 and 24 an El Niño took place followd by a La Niña, and one of the El Niños was the Super-El Niño of 1998. Strong solar cycles set off strong El Niño’s, and it takes time along with weaker cycles to dissipate the retained heat. Of course the PDO and time-of-year also seem to influence the ENSO cycle.
The Article
My plot (vertical scale is arbitrary)

Joel O'Bryan

Matt Zouders wrote, “why doesn’t the El Nino ratchet cause the ocean to spiral off into ever increasing levels of warmth?”
Those continent size areas of warmer surface waters moving outward east, then north and south, bring with them enormous water vapor convective potential. As the El Nino wanes they spread out north and south to hemisperic ITZCs. Massive convective activity is a negative feedback response, both transporting and transferring the latent heat through the evaporation-condensation cycle. Of course the clouds associated with all this tropospheric water vapor also substantially slows surface heating from incident solar irradiation and increases albedo. All these processes are coupled and separating (de-convolving) one from the other leads to the likely erroneous outputs due to the current models’ inabilities to correctly simulate all these interactions. Clouds, both their creation and effects, have frequently been cited as one of the modelers’s main uncertainties.

Joel O'Bryan

Matt Souders, sorry, not Zouders.


C shaped. Hmmmm. I bet it tastes like chicken too.

Greg Goodman

Quick lash-up graph of inverted SST and TLS
Not surprisingly, oceans take a while longer to react, but it looks to be the same step behaviour.

Greg Goodman

“If memory serves, the relationship falls apart before the 1970s.”
If you just take two ten year events like that Pochas, you could conclude that volcanoes are linked to solar cycles. too.

Joe Bastardi has an interesting idea about the oncoming El Nino. Whereas prior events were caused by conditions in the ocean itself, and thus able to perpetuate growth, Joe suggests the current event is caused by conditions over the landmass of Asia generating winds favorable to El Nino formation. Because conditions over inland Asia change so drastically from winter to summer, the “favorable” conditions will abruptly become “unfavorable,” resulting in the El Nino abruptly terminating, despite the fact it will start out like gang-busters. (Or that’s how I understood the idea; I could have it screwed up.)
It will be interesting to watch this event, to see if this El Nino behaves differently because the PDO is “cold.”


Is it possible Bob, now that Kevin’s opinion is incomplete. He assumes that these el ninos cause upward steps and this has definitely been true since 1976, but el ninos and these steps are not new. CO2 doesn’t cause these steps. This phenomenon has likely been going on as long as we have had oceans (at the very least since the continents became landlocked 2.5 million years ago creating the Atlantic and Pacific oceans we know today).
My point is that these steps occurred during a long-term warm PDO phase. Now that this phase has gone cool. Isn’t it likely that these steps will now REVERSE and each successive el nino, or at least big el nino events (such as 1983, 1988 and 1997) will bring about more cooler SST temperatures and, thus, earth temperatures?

Greg Goodman

Bob your animation looked interesting , so I tried to reproduce it .
I don’t find anything like what you showed in the graph. The range variability in NINO34. is less than a degree, in the 80,180E, -60,60N zone it about three degrees.
Did you scale or normalise or something?