Tag Archives: ENSO

El Nino Season Two?

It is like that stabby lady in the bath tub in that movie.

Here, I’ll give you a more readable version of the graphic from NOAA:

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The chance of an the Pacific ENSO system being neutral, meaning, not adding extra heat to the atmosphere and not removing extra heat form the atmosphere, is about 50% from now through mid 2017.

But, the chance of a la Nina is pretty darn low, and the chance of an El Nino, which would add more heat to the atmosphere than the average year, is not only approaching 40% but it has been growing.

A second El Nino this close on the last one, which was a very severe El Nino, will not be as strong because there is that much heat stored up in the Pacific. A lot of it came out last time. But there is a fair amount left in there, so we could have a real, if not major, El Nino event this summer or fall.

Or not. This is really up in the air, as it were. But it is a little unusual to see a second El Nino this close in time, so I thought you might find this interesting.

Global Warming Over The Next Decade: Candidates take note. UPDATED

The Time Scales of Political and Climate Change Matter

The US is engaged in the laborious process of electing a new leader, who will likely be President for 8 years. Climate change has finally become an issue in US electoral politics. The climate policies of the next US President, and the Congress, will have a direct impact on the climate, because those policies will affect how much fossil carbon is put into the atmosphere over coming decades. So it is vital to consider what the climate may do during the next administration and the longer period that will include that administration’s effective legacy period, more or less the next decade starting now.

There is evidence that the ongoing warming of the planet’s surface is likely accelerate in the near future. Recent decades have seen the Earth’s surface temperatures go up at a relatively slower than average rate compared to earlier decades. The best available science suggests that this rate is about to increase. We can expect a series of mostly record breaking months and years that will add up to an alarmingly warm planet.

(The graphic showing continued global warming through 2015 at the top of the post is from here.)

The Rate Of Global Warming Is About To Increase

I wrote about this last February, in discussing a paper by Steinmann, Mann, and Miller, that said:

The recent slowdown in global warming has brought into question the reliability of climate model projections of future temperature change and has led to a vigorous debate over whether this slowdown is the result of naturally occurring, internal variability or forcing external to Earth’s climate system. … we applied a semi-empirical approach that combines climate observations and model simulations to estimate Atlantic- and Pacific-based internal multidecadal variability (termed “AMO” and “PMO,” respectively). Using this method [we show that] competition between a modest positive peak in the AMO and a substantially negative-trending PMO … produce a slowdown or “false pause” in warming of the past decade.

That research was also discussed by Chris Mooney and John Upton. John Upton updated this discussion earlier this week, noting,

Cyclical changes in the Pacific Ocean have thrown earth’s surface into what may be an unprecedented warming spurt, following a global warming slowdown that lasted about 15 years.

While El Niño is being blamed for an outbreak of floods, storms and unseasonable temperatures across the planet, a much slower-moving cycle of the Pacific Ocean has also been playing a role in record-breaking warmth. The recent effects of both ocean cycles are being amplified by climate change.

Why Does The Rate of Global Warming Vary?

This is pretty complicated, and even those who are on the cutting edge of this research are cautious in making links between their models and the on the ground reality of warming in the near future. The long term rise in surface temperature, which is what we usually refer to when using the term “Global Warming,” is not steady and smooth, but instead, it is rather squiggly. But the ups and downs that accompany the general upward trend are mostly caused by things that are known.

The sun provides the energy to warm the Earth’s surface, and this contribution changes over time, but the sun varies very little in its output, and thus has less influence than other factors. The sun’s energy warms the Earth mainly because our atmosphere contains some greenhouse gasses. The more greenhouse gas the more surface warmth. As humans add greenhouse gas (mainly CO2 released by burning fossil fuel) the surface temperature eventually rises to a higher equilibrium. But the variation in the sun’s strength is hardly observable.

Aerosols, also known as dust or in some cases pollution (or airborne particles) can reduce the surface temperature by intercepting some of the Sun’s energy on its way to the surface (I oversimplify). These aerosols come mainly from industrial pollution and volcanoes. The addition of a large amount of aerosol into the atmosphere by a major volcanic eruption can have a relative cooling effect but one that lasts for a short duration, because the dust eventually settles.

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There are many other important factors. Changes in land use patterns that cause changes in effectiveness of carbon sinks – places where atmospheric carbon (mainly CO2) is trapped in solid form by biological systems – increase atmospheric CO2. Melting glacial ice takes up heat and influences surface temperatures. And so on.

The biggest single factor that imposes a squiggle on the upward trending line of surface temperature is the interaction between the atmosphere and the ocean. Close to 100% of the extra heat added to the Earth’s system by global warming ends up in the world’s oceans. The heat is moved into the ocean because the surface warms up (from the sun) but surface water is constantly being mixed into lower levels of the ocean, and visa versa. When it comes to the Earth’s surface temperature, the ocean is the dog and the surface is the tail.

A famous, and now perhaps infamous, example of this interaction between ocean and air is the El Niño Southern Oscillation (ENSO). Here’s the simple version (see here for more detail). The equatorial Pacific’s surface is constantly being warmed by the sun. The surface waters are usually blown towards the west by trade winds. (Those trade winds are caused in part by the rotation of the Earth, and in part by the ongoing redistribution of excess tropical heat towards the poles). This causes warm water to move west, where it is potentially subducted into the ocean, moving heat into the sea. That heat eventually may work its way out of the ocean through various currents.

During many years, the ins and the outs are similar. During some years, La Niña years, the amount of heat moving into the ocean is larger, which can cause a small cooling influence on the planet. Every now and then, the reverse happens. This involves complicated changes in trade winds and ocean currents. A good chunk of the heat that has been stored in the Pacific now emerges and is added very abruptly, over a period of several months, to the atmosphere. This is an El Niño event. We are at this moment experiencing one of the strongest El Niño events ever recorded, possibly the strongest (we won’t know until it has been going a while longer.)

ENSO is one, in fact the biggest, example of atmosphere-ocean interaction that influences surface temperatures. But, ENSO is only one part of the interaction between the Pacific and the atmosphere. There is also a phenomenon known as the Pacific Multidecadal Oscillation (PMO). For its part, the Atlantic has the AMO, a similar system. These phenomena are characterized by a general transfer of heat either into or out of the ocean, with several years in a row seeing more heat move into the ocean, followed by several years in a row of more heat moving out of the ocean.

Though ENSO and the PMO are distinct processes, they may be related. I asked climate scientist Michael Mann if he views El Nino as part of the larger scale system of PMO, or if El Niño essentially rides on top of, or acts independently from PMO. He told me, “I would say the latter. At some level, the PMO really describes the long-term changes in the frequency and magnitude of El Niño and La Niña events, i.e. change in the behavior of ENSO on multidecadal timescales, and it will appear as multidecadal oscillation with an ENSO-like signature with some modifications due to the fact that certain processes, like gyre-advection and subduction of water masses, act on longer timescales and do they are seen with the PMO bot not El Niño or La Niña.”

The influence of ENSO on global surface temperatures is well illustrated in this graphic from Skeptical Science.


Here, the surface temperature anomaly is shown from the late 1960s to the present. The annual values are classified into years during which ENSO was neutral, or neutral with volcanic influences, La Nina years, and El Niño years with or without volcanoes. A separate trend line is shown for years that should be relatively warm (El Niño), relatively cool (La Niña), and years that should be about average.

The influence of the PMO is also apparent.

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This graphic shows the measurement of the Pacific Decadal Oscillation and the surface temperature anomalies. The data are averaged out over a two year cycle (otherwise the PDO would be way too squiggly to be useful visually). Notice that during periods when the PDO is positive (adding heat to the atmosphere) there tends to be a stronger upward trend of surface temperature, and when the PDO is negative, the surface temperature rises more slowly. Remember, a lot of other factors, such as aerosols, are influencing the temperature line, so this relationship is quite imperfect.

Also notice that both lines trend dramatically upward near the end of the graph. This reflects the last couple of years (including right now) of dramatically increasing surface temperatures, and an apparent positive shift in the PDO. Just as interesting is the negative PDO associated with a reduced upward trend in the surface temperatures, fondly known by many as the “Hiatus” or “Pause” in global warming, during the first part of the 20th century. Indeed, it is likely that this slowdown (not really a pause) in warming is largely a result of a higher rate of excess heat being plowed into the oceans, and less coming back out. This is also a period during which the ENSO system produced no strong El Niños.

But the PDO is, as noted, part of a larger phenomenon of ocean-atmosphere interaction. The study noted above by Steinman, Mann, and Miller takes a broad view of these oscillations and their impact on climate. In RealClimate, Mann writes,

We focused on the Northern Hemisphere and the role played by two climate oscillations known as the Atlantic Multidecadal Oscillation or “AMO” … and the … Pacific Multidecadal Oscillation or “PMO”… The oscillation in Northern Hemisphere average temperatures (which we term the Northern Hemisphere Multidecadal Oscillation or “NMO”) is found to result from a combination of the AMO and PMO.

…Our conclusion that natural cooling in the Pacific is a principal contributor to the recent slowdown in large-scale warming is consistent with some other recent studies…

…the state-of-the-art climate model simulations analyzed in our current study suggest that this phenomenon is a manifestation of purely random, internal oscillations in the climate system.

This finding has potential ramifications for the climate changes we will see in the decades ahead. As we note in the last line of our article,

Given the pattern of past historical variation, this trend will likely reverse with internal variability, instead adding to anthropogenic warming in the coming decades.

That is perhaps the most worrying implication of our study, for it implies that the “false pause” may simply have been a cause for false complacency, when it comes to averting dangerous climate change.

What Will Global Warming Do During The Next Decade?

Have political leaders and representatives been lukewarm on climate change over recent years in part because the climate change itself has been less dramatic than it could be? And, conversely, is it the case that the next couple of decades will see a reverse in both? I asked Michael Mann if his research indicated that the indicators such as the PMO, AMO, or the derived NMO, show that the oceans are about to contribute to a speedup in warming. He told me, “…both PMO and AMO contribute to NMO, but in recent decades PMO has been the dominant player, and yes, I would expect to see the recent turn toward El Nino-like conditions and enhanced hemispheric/global warming as an apparent upturn in the NMO, though it is always difficult if not impossible to diagnose true change in the low-frequency signal right at the end of a time series.”

Let’s have a closer look at the influence of the PDO on global surface temperatures. Since the human influence on the atmosphere has grown over time, we want to focus on more recent decades when the input of additional greenhouse gases had already risen to a high level. This graphic shows the NASA GISS surface temperature anomaly values (the dots) from 1980 to the present, but with some trend lines added in.

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(The NOAA GISS data are a running 12 month mean using the monthly data. Note that the trend lines added to this graph are meant to visually underscore the differences between time periods in the overall trend, and have no special statistical value.)

The black dots and the curvy trend line to the left represent a period of time when the PDO was positive, but also includes a depression in surface temperature because of the eruption of Mount Pinatubo. I made the trend line a “second order polynomial” instead of a regular straight line. A polynomial equation can capture internal curviness of a series of data.

(A polynomial equation that is of the same “order” as the number of points in the data set would, theoretically, zig and zag back and forth to account for each data point’s position which would be absurd. One must be careful with poylnomials. But a second order polynomial can honestly reflect a modest curviness in a series of data, and in this case, helps the line do its job at visually presenting a short term pattern.)

The second series of data, in blue, shows a period of mostly negative PMO, again, with a second order polynomial line drawn on it. This is the period of time that includes the so-called “hiatus” in global warming, when the upward trend of increasing surface temperature was somewhat attenuated. That attenuation was probably caused by a number of factors, and in fact, at least one of those factors had to do with inadequacies of the data itself, in that the measurements fail to account for extreme warming in the Arctic and parts of Africa. But the negative PMO, and likely, according to Steinmann, Mann and Miller, a larger scale relationship between atmosphere and ocean, seem to have somewhat flattened out the line.

But then we come to the third part of the data, in red. The ocean-atmosphere relationship has switched the other way. The PMO has been positive since the last part of 2013, and over a smaller and more recent time frame, we have been experiencing a strong El Niño.

This graphic does a nice job showing how short and medium term upward and downward trends eventually cancel out to produce a single upward trend in global surface temperature. Very short term shifts such as a given El Niño event or a given Volcanic eruption cause the most obvious squiggles. Somewhat longer term, multi-decade trends such as the PDO cause longer parts of the series of measurements to rise more or less quickly. But over nearly 40 years shown here, and longer periods, all the ups and downs average out to a single trend that can be reliably projected for a reasonable period of time.

Will More Rapid Global Warming Spur A More Effective Policy Response?

These ups and downs in the rate of warming are not important to the long term trend, but they are important because of their immediate effects on weather. And that is all that should matter. But these short and medium term trends, as well as even more immediate events such as individual storms, take on a greater importance that has nothing to do with the science of climate change itself. These changes affect the way politicians, advocates, and the general public, regard climate change, and serve to motivate or attenuate action on one side of the false debate or another.

We have known enough about climate change and its causes to have started the shift from fossil fuels to alternative strategies for producing energy long before 1980, but have in fact done very little to solve this problem. Initially, climate change seemed more like a thing of the future, and in fact, had relatively little impact on the most influential and powerful nations and people. Disruptions of weather patterns started to become more apparent around or just before 1980, but for the next few decades anti-science forces were well organized, and their efforts were enhanced, at the beginning of the 21st century, by the unthinking and unknowing process of air-sea interactions that reduced the rate of surface temperature increase even while weather patterns continued to become more and more chaotic.

But the truth is, a widespread flood in the American bottomlands defeats a snowball in the hands of a contrarian Senator. Eventually, more and more people in the US have been affected by inclement weather, and the frequency with which destructive storms of various kinds hammer the same subpopulation again and again has gone up. The symbolic snowball melts under the cold hard stare of voters who wonder how they are going to rebuild their lives after floods, severe storms, and droughts have taken away their property, in some cases their loved ones, and raised their insurance rates.

So the question emerges, will the next decade or so be a period of increased, or of attenuated, motivation from Mother Nature to act on climate change? The rational actor will act now, because we know that the greenhouse gas we pump into the atmosphere today changes the climate for decades to come. The reactionary actor with little capability or interest in thinking long term (i.e. most people) will be mollified by a decade with few severe storms, not much flooding, a seemingly secure food supply, and a snowball or two.

I left the projection of the future as a single estimate based on the past several decades (all the data shown on the graph). I could have imposed a more upward trending line, maybe a nice curve like these polynomials show, as an extension to the blue line. But since the graphic is going out a couple more decades, and the ups and downs average out over several decades, I think it is fair enough to use the linear projection shown by the red dotted line.

I’m not actually making a prediction of future global surface temperatures here. What I’m showing instead is that two things seem to be true. First, long term (over decades) global warming has happened and will likely to continue at about the same pace for a while. This has been going on long enough that by now we should viscerally understand that the squiggles are misleading. Second, the last couple of decades have been a period of reduced warming, but that period is likely over, and we are likely to experience an increased rate of warming.

Will surface temperatures during the term of the next POTUS squiggle about mostly above that red dotted line on this graph, or will those temperatures squiggle up and down above and below the line, or even below it? Based on the best available science, that first choice is most likely. Whomever ends up being POTUS, and the corresponding Congress, will be enacting (or failing to enact) policy during a period of surface temperature increasing at a rate higher than we have in recent years.

A vitally important known unknown, is what will the effects of such a rise in surface temperature be. We have various levels of confidence that storminess, changes in the distribution of rainfall, drought, and through the melting of glacial ice, sea level rise, are all important forms of climate disruption we are currently experiencing, and we should expect more of the same. The unknown is whether or not we should expect a dramatic acceleration of these changes in the short term future.

How will the insurance industry address an increase in widespread catastrophic damage caused by storms and floods? Will the government have to underwrite future losses, or will disaster insurance simply become something we can’t have? Will there be damage to our food production system that ultimately results in less certainly in the food supply, and how will we deal with that? The well known “reugee crisis” is a climate refugee crisis. But it may be a small one compared to what could happen in the future. Will we need to restrict development in mountain areas more subject to fires, and withdraw settlement from low lying areas along major rivers? How will we address more widespread and more severe killer heat waves?

The battle to preserve the use of fossil fuels exists at the state level in the US. Should we have a national effort to stop the legislatures in red states from putting the kibosh on local development of clean energy sources, either by energy utilities or individual home owners?

Sea level rise has already had several negative effects, but it is also is a longer term issue, and is perhaps among the most serious consequences of human greenhouse gas pollution. At some point, American politicians in some areas will be faced not with the question, “Will this or that Congressional district be represented by a Democrat or a Republican,” but rather, “Where the people who lived in this district go now that the sea is taking it?”

Over time, I think the social and political will to address climate change has grown, though very slowly. It might seem that the effects of climate change right now are fairly severe, with floods and fires and all that being more common. But while these effects are real and important, they have been minor compared to what the future is likely to bring. The anemic but positive growth of willingness to act has occurred in a political and physical climate that is less than nurturing of dramatic and effective action.

Whoever is elected president this time around, and the Congress, will serve during a period when the people’s will to act will transform from that inspired by activists pushing for change, to outcries of a larger number of desperate and suffering newcomers to the rational side of the climate change discussion.

Expect a sea change in the politics of science policy.

Added: See this recent post by Peter Sinclair, and his video:

An Improved Classification And Explanation For El Nino (New Research)

A new study seems to provide a better way to categorize El Nino climate events, and offers an explanation for how different kinds of El Nino events emerge.

El Nino is part of a large scale, very important climate phenomenon in the Pacific Ocean, generally referred to as the El Nino Southern Oscillation (ENSO). Over time (years) wind and water currents move heat into the upper levels of the Equatorial Pacific (La Nina). Then, over time (months) the heat comes back out – that is an El Nino. The effects can be dramatic. During El Nino years, trade winds and monsoons may behave differently than normal. How much precipitation falls and where it falls can change over large regions. Deserts become lakes, good croplands are drought stricken, sea levels change across large portions of the coast.

It is interesting to contemplate the following thought experiment (sorry, a bit of a digression). Imagine if all of the conditions associated with El Nino happened all the time, and had been happening for centuries. An El Nino that is always there is not really an El Nino. It is normal. Those parts that are dry would be dry; Plants and animals, including people, would be dry adapted there in physiology, ecology, and behavior. Same for wet places. It wouldn’t be a desert covered with a lake, it would just be a lake. It wouldn’t be a drought, but just a desert. Etc. The point of this is to underscore the real meaning of El Nino: change. It isn’t so much what it does, but rather, that this climate event’s effects are sudden, dramatic, and occasional.

El Nino has been off and on in the news over the last year or so because it looked like there was going to be a really big one in 2014, but it never materialized. (Even without an El Nino, which warms the surface of the Earth, 2014 was still a record breaking warm year.) Now, El Nino is in the news again because finally we kinda sorta are having one, and a future (this year and next) super double El Nino is being predicted.

Why is El Nino prediction so difficult, and why, when an El Nino happens, it may be very different from some other El Nino that happened before in its overall intensity and in the details of what it causes to happen elsewhere in the world?

You can hear them screaming. The climatologists. “Why? Why? WHY?!?!?” Because this is a really a big thing and it would be really nice to be better at predicting it.

A new study has taken an important step in understanding, and ultimately, predicting El Nino. “Strong influence of westerly wind bursts on El Nino diversity” by Chen et al, published in Nature Geoscience, makes two related points. First, the authors presupposed the existence of three kinds of El Ninos. It has long been thought that El Ninos can be classified into different categories, but the number and nature of those categories varies across groups of researchers. I asked the author if they tried using other a priori numbers for the El Nino categories. “Yes, we did try using other cluster numbers,” Dr. Chen told me. “If it’s set to 2, we would have the extreme El Nino and a broad cluster that include both the canonical and the warm-pool El Nino. If it’s set to 4, we would still see the 3 types we identified but with a 4th type that’s not well separated from the canonical El Nino. In any case we had only one type of La Nina. These discussions will be included in a long paper to be submitted to Journal of Climate.”

Chen et al used a method of modeling El Nino that is different than what is usually done and with this method successfully classified all of the El Nino events over a 50 year time period into these three categories. Second, Chen et al show that the main variable that determines what kind of El Nino happens is the intensity and location of westerly wind bursts (WWBs). I also asked if other variables used in their model (discussed below) were changed to see what would happen. Dr. Chen noted, “we did play with different model settings and parameters, and the outcome turned out to be fairly robust. We are very confident with our results.”

First a brief note on the method. The usual way of managing the complex phenomenon of El Nino … of measuring stuff and stuffing the measurements into a mathematical model … is called empirical orthogonal function (EOF) analysis. This involves measuring key variables across a grid covering the Pacific Equatorial region. Then you take the measurements and simplify how they are organized and turn a multidimensional time-space problem in to a one with fewer dimensions. There are different ways to do this but they all fall into the widely used methodology that included principle component analysis and other things you may be familiar with. You take something really complicated and derive simplified (somewhat) data that is more usable for characterizing a phenomenon or predicting the phenomenon’s behavior while at the same time not throwing away too much of the meaningful variation in the system. This method, however, if fairly linear and deterministic. A bunch of variables are thought to cause outcome A (which has variants), and this bunch of variables are combined so you have only X and Y causing A.

Chen et al applied a different (but well established) technique that presumes less about the linear nature of the model’s components and allows for complex interrelationships that may vary across conditions to remain. It is called fuzzy clustering method. In this method, the data are allowed to decide on their own (more or less) how they should be organized, and (this is the fuzzy part) individual bits of data are actually allowed to occupy more than one cluster. For many systems, the two methods would result in similar outcomes, but when a system is less linear the second method may be more realistic.

When this method is used, the role of WWBs turns out to be very important. This is not entirely new because we already knew that westerly winds across the Equatorial Pacific were important in ENSO cycles. The ENSO cycle involves, to simplify a bit, heat at the surface of the Pacific moving westward and then into the deep (but not to deep) ocean where it builds up. This process is maintained by currents and winds moving from east to west. It is a little like the air near your ceiling growing ever hotter if you burn wood in your stove; In that case the property of warm air rising causes the upper few feet of your living room to get much hotter than the floor. The Western Pacific gets hotter over time because winds and currents push the heat there.

This build up in heat (and other factors) eventually cause a change in the movement of heat and we see warm water moving east, surfacing, and transferring heat energy into the air. That is an El Nino.

From the abstract of the paper:

We propose a unified perspective on El Nin?o diversity as well as its causes, and support our view with a fuzzy clustering analysis and model experiments. Specifically, the interannual variability of sea surface temperatures in the tropical Pacific Ocean can generally be classified into three warm patterns and one cold pattern, which together constitute a canonical cycle of El Nin?o/ La Nin?a and its different flavours. Although the genesis of the canonical cycle can be readily explained by classic theories, we suggest that the asymmetry, irregularity and extremes of El Nin?o result from westerly wind bursts, a type of state-dependent atmospheric perturbation in the equatorial Pacific. Westerly wind bursts strongly affect El Nin?o but not La Nin?a because of their unidirectional nature. We conclude that properly accounting for the interplay between the canonical cycle and westerly wind bursts may improve El Nin?o prediction.

The authors demonstrate that accounting for WWBs does a better job of retroactively predicting the different kinds of El Nino events that have happened over the last fifty years. They conclude that El Nino may result from a combination of the built in see-saw effect of build up of ocean heat in the west and the reversal of movement of warm water on one hand and WWB perturbations, with the pattern of westerly winds affected by the oscillation itself. (I am over simplifying ENSO here, see below for resources on how it works.) Whether or not an El Nino happens is predicted by the classic oscillation model, but which kind of El Nino results is better predicted by the WWBs. From the study:

Such a scenario is appealing because it reconciles hotly debated issues related to the classification and genesis of various El Nin?o events, by killing three birds — diversity, asymmetry and extremes — with one stone. But one must not dwell on the simplicity of the picture painted here. Our intention is to emphasize the strong influence of WWBs on El Nin?o diversity, but not to downplay other processes that may play significant roles in El Nin?o dynamics and thus contribute to the complexity of its diversity.

The research reported here does not address, but may relate to, a set of questions that have been on my mind as I’ve watched El Nino and the discussion surrounding it develop over the last year or so. Is El Nino (or ENSO, more broadly) changing because of climate change? Since El Nino was already hard to predict, we can chalk up this last round of lousy predictions as El Nino being El Nino. But we might also ask the question, is it possible that as more surface and upper ocean heat enters the system, are there changes? Chen et all actually do note that “… real-time El Nin?o forecasting remains an elusive and formidable goal. This is probably because predictability estimates were mainly based on models dominated by a single mode of El Nin?o variability or on hindcast skills of relatively large El Nin?o events, whereas in reality El Nin?o has a variety of flavours, especially in the past decade” (emphasis added). So, these folks, referring to other research, note that El Nino has changed. Is this random variation with no important linear time dimension, or is it a “new normal” for the already normal-defying El Nino, or, perhaps, is it the first part of a period during which ENSO changes dramatically to a climate controlling phenomenon that acts differently in important ways?

Michael Tobis, an expert on atmospheric and ocean systems, suggested to me that “…the real action in climate change is where the warm water goes, not what the wind does. The wind will respond, and may reinforce or mitigate what the ocean does, true. But as the ocean water mass gets further from its recent near-equilibrium, eventually wind stress coupling becomes a smaller deal and the water will go where it will go.” Tobis also notes, and Chen et al acknowledge this may be important, that “the most salient feature in the oceans right now is the large and persistent warm blob in the eastern North Pacific.” This implies (i.e., causes me to speculate or, really, guess) that a warming ocean may shift the balance of what is important in driving, or resulting from, ENSO dynamics. That does not detract from Chen et al’s apparent ability to both classify and explain the differences between El Nino events with WWBs being the key factor.

I asked Dr. Chen to go out on a limb a bit to discuss what the future may hold as climate changes.

Question: With global warming, ocean heat (both at some depth and SST) has increased. Since heat in the ocean is a key variable in ENSO cycles, is it possible that El Nino dynamics would change in some important way, for example, of the three flavors of El Nino, the relative likelihood of which flavor manifesting changing? Is there evidence that such a change may have already occurred, thus the dismal level of predicability of 2014/5? Or, would you expect such a change in the future? My gut feeling is that El Nino dynamics is a barely stable metastable system that is in sufficiently weak equilibrium that it could change to a different equilibrium if important inputs are changed a lot.

Answer: I think your gut feeling is right, in the sense that El Nino is changing under global warming. The questions are how and why. Observations over the last 15 years seem to indicate that the system is now dominated by the warm-pool El Nino, while some people use IPCC model projections to argue that in the future the extreme El Nino will become more frequent. These are still open questions.

Second version of the same question: I’ve heard El Nino/ENSO described as a quasi equilibrium. The essential feature of this system is shifting back and forth between recharge and discharge of ocean heat. Is a different system imaginable where this is not a cyclic system, but rather, a steady state system (such as we see with the Atlantic Conveyor or other climate systems) with heat going in (somewhere) and coming out (somewhere else) more or less steadily? Since we are entering global temperature levels not seen in a long time (and thus only represented in ancient paleo records of lower quality) it seems like it can’t be ruled out (other than it being a rather extreme idea)

Answer: In the recent history and perhaps also during many periods in the past, ENSO did behave like a self-sustaining oscillation. However, it is quite possible that the system might enter a steady state — a permenant El NIno or La Nina state — when external forcing changes.

Question: Figure 4 (see top of post) seems to show something rather astonishing (aside from that figure’s use to demonstrate WWB and WWV association with different kinds of El Nino): WWB in 2014 was very high and uniquely so. Why? Other than the apparent fact that this WWB was not followed by a strong El Nino (a key point of your paper) is there anything else interesting about this?

It all depends on the interplay between the WWB and the basic cycle (measured by WWV). Only when the former occurs at the right phase of the latter a large El Nino will take place. It is true that WWBs were very strong in 2014, but only in the early year, not over the entire spring season. Further experiments will be needed to clarify whether or not the relationship between WWB and WWV will change under global warming.

It will certainly be interesting to see, over the next 24 months or so, if we end up having a strong El Nino, a double El Nino, or if we have lapsed into an extended period of what some are calling El Annoyingo.

For more information about El Nino:

Is a Powerful El Niño Brewing in the Pacific Ocean?

Fishing in pink waters: How scientists unraveled the El Niño mystery

El Niño/Southern Oscillation (ENSO) Technical Discussion

El Niño: How it works, how we observe it

Check out: The First Earth Day, an epoch journey into politics, explosions, folk music, and old boats floating on stinking rivers.

New Research Suggests Global Warming Is About To Heat Up

A paper just published in Science Magazine helps explain variation we see in the long term Carbon-pollution caused upward trend Earth’s surface temperatures. The research also, and rather ominously, suggests that a recent slowdown in that trend is likely to reverse direction in the near future, causing the Earth’s surface temperature to rise dramatically.

The graph shown above represents the ongoing warming of the Earth’s surface owing to the increased atmospheric concentration of human generated greenhouse gas pollution, mainly CO2. But, have a look at the following graph of changes in concentration of CO2 in the Earth’s Atmosphere:


As you can see, the increase in CO2 is very steady, while the changes in Earth’s surface temperature is very squiggly. Why? In particular, the Earth’s surface temperatures seem to undergo a series of rapid increases or decreases, and now and then, seem to squiggle up and down along a slowly ascending plateau, as has been happening recently. Climate science deniers have taken this recent slowing in the increase of temperature as a signal that the link between CO2 concentrations and global surface temperatures is a hoax. But real climate scientists focus instead on actually explaining, rather than making up stories about, this variation.

There are several different factors that may cause the shorter term squiggles that we see superimposed on the longer term warming trend. The sun’s energy varies over decades, and this contributes a small amount to the variation. Aerosols (dust), either from human activities or volcanic activity, can produce a cooling effect, and this effect varies across time. If you look at the graph of temperatures, you’ll see a strong downward trend associated with the vast eruption of Mount Pinatubo in 1991, for example. A third source of variation in the upward march of the Earth’s temperature is not really a source of cooling or heating at all, but rather, a shift in where the heat goes. The graph on the top of this post is of “surface temperature,” which is a combination of land-based thermometers at roughly head-height, located at weather stations around the world, and sea surface temperatures. But well over 90% of the heat added to the Earth’s system by the human-caused greenhouse effect actually ends up in the ocean. A small percentage of variation in how much heat goes into, or comes out of, the ocean can cause a large variation in the “surface temperature.” You can think of the surface temperature measurements as a relatively small tail attached to a rather large dog, where the dog is the ocean and the tail is the land based thermometers and the sea surface. (I’ve developed this analogy here.)

That the behavior of the ocean is important can be understood by noting that while surface temperature increase has slowed in recent years, the temperature in the top couple of kilometers of the world’s oceans has continued to increase apace. You can also look at the relationship between the squiggle of the surface temperature curve and El Niño and La Niña events. The former are periods of time when the Pacific ocean is sending heat out into the atmosphere, and the latter are periods of time when the Pacific is sucking more heat in. The following graphic from Skeptical Science illustrates this nicely.


“ENSO” refers to the El Niño-La Niña cycling. The top line, in red, represents the change over time in surface temperature just during El Niño periods, while the blue line, along the bottom, represents change over time in surface temperature just using La Niña years. As you can see, many of the ups and downs in the long term surface temperature trend seem to represent ENSO variation.

Now, to the recently published study. The paper is “Atlantic and Pacific multidecadal oscillations and Northern Hemisphere temperatures” by Byron Steinmann, Michael Mann, and Sonya Miller, and is published in tomorrow’s Science. (Yes, I have a time machine.) From the abstract:

The recent slowdown in global warming has brought into question the reliability of climate model projections of future temperature change and has led to a vigorous debate over whether this slowdown is the result of naturally occurring, internal variability or forcing external to Earth’s climate system. To address these issues, we applied a semi-empirical approach that combines climate observations and model simulations to estimate Atlantic- and Pacific-based internal multidecadal variability (termed “AMO” and “PMO,” respectively). Using this method, the AMO and PMO are found to explain a large proportion of internal variability in Northern Hemisphere mean temperatures. Competition between a modest positive peak in the AMO and a substantially negative-trending PMO are seen to produce a slowdown or “false pause” in warming of the past decade.

The research (also reviewed here by Chris Mooney) combines observational data (temperature records and the indices for the AMO and PMO) with sophisticated modeling techniques to parse out the contributions of the Pacific and Atlantic oceans, the big dogs of climate change (the Pacific being the much bigger dogs) on surface temperature variability. Essentially, they are trying to determine how much of the squiggling, specially the recent slowing down of temperature increase, is accounted for by “internal variability” as opposed to “forcings.” The former includes the interactions of the surface and the ocean. “Forced” variation is, according to Michael Mann, means “… governed by drivers, be they human (increased greenhouse gas concentrations, sulphate pollutants) or natural (volcanoes, solar output changes). The internal variability is what’s left, it is the purely natural oscillations in the system that have no particular cause, just as weather variations on daily timescales have no particular cause, they just happen.”

One of the findings of this paper, important in climate research but perhaps a bit esoteric, is that the Pacific and Atlantic have mostly independent effects as sources of internal variation. This is not really new, but confirmed by this work. More exactly, treating them as independent provided good results.

But the most important finding is summarized in the following figure, taken from Figure 3 and also reproduced in a writeup by author Mann at Real Climate:


This shows the AMO, PMO, and the derived (combining the two) NMO values over time. Assume that the highest and lowest values are close to the maximum and minimum that these measures normally reach. Note that there is something of a periodicity in these values. That there would be makes sense. These values represent the way in which the oceans interact with the air, and we know that although there is not perfect periodicity (regularity) in that relationship, historically, every year the ocean is in a phase of removing heat from the atmosphere there is an increased chance of a reversal in that relationship. Now, step back from the contentious issue of climate change for a moment, and imagine that these are values of a blue chip stock you are thinking of investing in. Remember the cardinal rule of getting rich on the stock market: Buy low, sell high! Now, decide if you want to put your hard earned money ito the AMO or the PMO. Clearly, the PMO is at a minimum. Buy now because it is going to go up soon!

Remembering that the PMO was found to be a much bigger source of internal variability than the AMO, and that it is a major player in determining surface temperatures, this can only mean one thing. Things are going to heat up soon. Study author Michael Mann told me, “The PMO appears to be very close to a turning point, based on the historical pattern. So we don’t expect it to continue to plunge downward. We expect a turning point soon.” In his summary of the work in Real Climate, Mann notes that “the most worrying implication of our study [is] that the “false pause” may simply have been a cause for false complacency, when it comes to averting dangerous climate change”

We just had the warmest calendar year on record. Last month, January 2015, was probably the second warmest January on record. Using a 12 month moving average (like in the graph at the top of this post), the last 12 months were the warmest 12 months on record. I hear rumors that February, the month we are in, is relatively warm. We have been seeing signs of the Pacific belching out more heat lately, with El Niño threatening. This could all be a very short term trend, as we expect to happen frequently with the general upward march of surface temperatures owing to greenhouse gas pollution. But this latest paper indicates that it might not be; it could be the beginning of a longer upward trend. Whatever effects of surface warming you might be concerned with — increased storms, drought, more rapid melting of glacial ice, killer heat waves — expect more over the next decade than we have over the last decade. And we had quite a bit of that over the last decade.

El Nino and Global Warming: Graphics

Here are a couple of helpful graphics looking at global warming in relation to ENSO events. During La Nina years, we expect the earth to cool(ish). During El Nino years we expect the earth to warm(ish). This pattern sort of cycles over several years, with neutral years in between (it isn’t a very regular cycle). The influences of the tropical Pacific, manifest as La Nina and El Nino periods is then, of course, superimposed over the longer term warming trend caused by increase of greenhouse gases in the atmosphere. Technically, 2014, which was the warmest year during the instrumental record beginning in the 19th century, was a neutral year, though there were some El Nino tendencies.

This graph, from Climate Central, helps show this relationship:

Original caption: Global annual average temperature anomalies (relative to the 1961-1990 average) for 1950-2013, based on an average of the three data sets from NASA, NOAA and the U.K. Met Office. The January-to-October average is shown for 2014. The colouring of the bars indicates whether a year was classified as an El Niño year (red), an ENSO neutral year (grey) or a La Niña year (blue).
Original caption: Global annual average temperature anomalies (relative to the 1961-1990 average) for 1950-2013, based on an average of the three data sets from NASA, NOAA and the U.K. Met Office. The January-to-October average is shown for 2014. The colouring of the bars indicates whether a year was classified as an El Niño year (red), an ENSO neutral year (grey) or a La Niña year (blue).

Dana Nuccitelli is the master of animated climate change graphs. He has produced a graph that shows the surface temperature record for only La Nina years, only El Nino years, and all the years together, in a way that makes the point. The original graphic can be found here, and further discussion of it can be found here. Here is the moving GIF … but if it doesn’t move for you go to one of the provided links and get to the original version.


So, are we going to have an El Nino, or what?

Officially, 2014 closed without an official El Nino. Probably. If you went back in a time machine to the spring, and told El Nino watchers that, they would be a little surprised, but they would also say something like, “Yeah, well, you know, we keep saying this is hard to predict.”

Despite the fact that for the most part there was not an official El Nino declared, a subset of El Nino conditions have been around, off and on, for many months. To officially declare an El Nino, a number of things have to add up, and while some of those things developed, the standard was not met. A few weeks ago, the Japan Meteorological Agency did retroactively say that there had been an El Nino, but others are not really going along with that. Some agencies are saying something similar but with less certainty.

Over the last few days, a number of new statements about El Nino have come out, and it looks like we are not too likely to see a large El Nino in 2015, but maybe a weak one. Or maybe none. (But some who watch this phenomenon have quietly suggested there could be a strong one.) Here are some of those statements.

Let’s start with the Australian Bureau of Meteorology ENSO Wrap-Up:

Tropical Pacific Ocean moves from El Niño to neutral
Issued on 20 January 2015
Since late 2014, most ENSO indicators have eased back from borderline El Niño levels. As the natural seasonal cycle of ENSO is now entering the decay phase, and models indicate a low chance of an immediate return to El Niño levels, neutral conditions are considered the most likely scenario through into autumn.

Central tropical Pacific Ocean surface temperatures have fallen by around half a degree from their peak of 1.1 °C above average in late November. Likewise, the Southern Oscillation Index has weakened to values more consistent with neutral conditions, while recent cloud patterns show little El Niño signature. As all models surveyed by the Bureau favour a continuation of these neutral conditions in the coming months, the immediate threat of El Niño onset appears passed for the 2014–15 cycle. Hence the ENSO Tracker has been reset to NEUTRAL. The Tracker will remain at NEUTRAL unless observations and model outlooks indicate a heightened risk of either La Niña or El Niño developing later this year.

From NOAA’s climate prediction center, from a statement issued on January 8th, 2015:

Although the surface and sub-surface temperature anomalies were consistent with El Niño, the overall atmospheric circulation continued to show only limited coupling with the anomalously warm water. The equatorial low-level winds were largely near average during the month, while upper-level easterly anomalies continued in the central and eastern tropical Pacific. The Southern Oscillation Index (SOI) remained slightly negative, but the Equatorial SOI remained near zero. Also, rainfall remained below-average near the Date Line and was above-average over Indonesia (Fig. 5). Overall, the combined atmospheric and oceanic state remains ENSO-neutral.

Similar to last month, most models predict the SST anomalies to remain at weak El Niño levels (3-month values of the Niño-3.4 index between 0.5oC and 0.9oC) during December-February 2014-15, and lasting into the Northern Hemisphere spring 2015 (Fig. 6). If El Niño were to emerge, the forecaster consensus favors a weak event that ends in early Northern Hemisphere spring. In summary, there is an approximately 50-60% chance of El Niño conditions during the next two months, with ENSO-neutral favored thereafter (click CPC/IRI consensus forecast for the chance of each outcome).

And now a shout out from NOAA, January 15th:


(I thought they were going to stop using all caps.)

From the International Research Institute for Climate and Society, Columbia University, IRI ENSO forecast:

During December 2014 through early January 2015 the SST exceeded thresholds for weak Niño conditions, although the anomaly level has weakened recently. Meanwhile, only some of the atmospheric variables indicate an El Niño pattern. Most of the ENSO prediction models indicate weak El Niño conditions during the January-March season in progress, continuing through most or all of northern spring 2015.

And now a few pullouts from the January 19th ENSO: Recent Evolution, Current Status and Predictions report from NOAA, a PDF file chock full of graphics and stuff put out every month.

This table (of ONI Index values) puts the current year in context of previous El Nino (red) and La Nina (blue) seasons. It is interesting to look at how long it has been since the last strong El Nino event. Most of 2012, and all of 2013 and 2014, qualify as being enough of anything by this measure to call it anything other than Neutral.

Screen Shot 2015-01-20 at 10.07.36 AM

This graphic summarizes the chance of El Nino over coming months.

Screen Shot 2015-01-20 at 10.08.03 AM

ENSO Alert System Status: El Niño Watch
ENSO-neutral conditions continue.
Positive equatorial sea surface temperature (SST) anomalies continue across
most of the Pacific Ocean.
There is an approximately 50-60% chance of El Niño conditions during the
next two months, with ENSO-neutral favored thereafter.

So, did we have an El Nino? Not officially, though some features that make up this phenomenon were present, off and on, over the last several months. Will we have an El Nino? Well, the indications we are having now are not too different than what we have been having, so who knows? My personal opinion is that the last year and the coming months together are going to have to be looked at carefully to determine if the way in which El Nino is measured need to be tweaked. But, that is nothing new, there is an ongoing conversation among climatologists about this.

The graphic at the head of the post is from “Fishing in pink waters: How scientists unraveled the El Niño mystery.”