Guest post by Bob Tisdale
OVERVIEW
This post compares satellite-based Sea Surface Temperature (SST) anomalies to the hindcasts and projections of the multi-model mean of CMIP3 models. CMIP3 is the archive the IPCC used as the source of their models for AR4. The period being discussed runs from November 1981 to November 2011. This covers most of the recent warming period that began in the mid-1970s.
There are two modes of natural climate variability discussed in this post: the El Niño-Southern Oscillation (ENSO) and the Atlantic Multidecadal Oscillation (AMO). For those new to ENSO, refer to An Introduction To ENSO, AMO, and PDO – Part 1. And for those new to the AMO, refer to An Introduction To ENSO, AMO, and PDO — Part 2.
This post also illustrates the multiyear aftereffects of the 1986/87/88 and 1997/98 El Niño events on the Sea Surface Temperature anomalies of the Atlantic, Indian, and West Pacific Oceans. Those oceans cover approximately 67% of the surface area of the global oceans. I have presented the processes that cause the multiyear aftereffects of those ENSO events in numerous posts over the past few years, so they will not be discussed in detail in this post. For those interested in learning about those processes, I discussed them and illustrated them with time-series graphs and with animated maps of sea surface temperature anomalies and other variables, most recently, in a two-part series: ENSO Indices Do Not Represent The Process Of ENSO Or Its Impact On Global Temperature and Supplement To “ENSO Indices Do Not Represent The Process Of ENSO Or Its Impact On Global Temperature”.
NOTE: The data in this post have been adjusted for the effects of volcanic aerosols.
INTRODUCTION
In the recent series of posts that compare the IPCC hindcasts for 20th Century surface temperatures to observed surface temperatures (see here, here, here, and here), the only time period when models consistently agreed with observations was the late warming period, from 1976 to 2000. But even that is misleading, because it gives the incorrect impression that anthropogenic forcings such as Carbon Dioxide were responsible for the rise in surface temperatures. Illustrating the error in that assumption is relatively easy when Sea Surface Temperature anomaly data is adjusted for the impacts of major volcanic eruptions and when the global data is divided into two subsets: the East Pacific (coordinates of 90S-90N, 180-80W) and the Rest-Of-The-World (90S-90N, 80W-180). Refer to the map in Figure 1 for an illustration of those areas. And Figure 2 is a comparison of the Sea Surface Temperature anomalies for those two subsets.
Figure 1
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
Figure 2
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
DATA
The Sea Surface Temperature anomaly data used in this post is Reynolds OI.v2. It combines bias-corrected satellite observations for more complete coverage and in situ observations from buoys and ships. The Reynolds OI.v2 Sea Surface Temperature data covers the period of November 1981 to November 2011, or 30 years. The Reynolds OI.v2 data is available through the NOAA NOMADS website here. There is another reason why the Reynolds OI.v2 data is used in this post: Smith and Reynolds (2004) Improved Extended Reconstruction of SST (1854-1997)stated about the Reynolds OI.v2 data:
“Although the NOAA OI analysis contains some noise due to its use of different data types and bias corrections for satellite data, it is dominated by satellite data and gives a good estimate of the truth.”
The truth is a good thing.
We’ll also be using the multi-model mean of the Sea Surface Temperature data that was produced by the climate models in the CMIP3 archive, where CMIP3 stands for Phase 3 of the Coupled Model Intercomparison Project. CMIP3 is the archive the IPCC used as the source of climate model data for its 4th Assessment Report. The CMIP3 Sea Surface Temperature data, identified as TOS, is available through the Royal Netherlands Meteorological Institute (KNMI) Climate Explorer website, specifically at their Monthly CMIP3+ scenario runswebpage. We have discussed in the recent posts that the multi-model mean represents the natural and anthropogenic forced component of the IPCC’s climate model outputs. And during the period we’ll be evaluating, it is the IPCC’s contention that anthropogenic forcings are the cause of the rise in surface temperatures.
The last discussion about the data is how the adjustments were made to account for the volcanic aerosols. The observational and model mean data are adjusted for the effects of volcanic aerosols, which would have major impacts on how the data was perceived during and for a few years after the explosive volcanic eruptions of El Chichon (1982) and Mount Pinatubo (1991). To determine the scaling factor for the volcanic aerosol proxy, I used a linear regression software tool (Analyse-it for Excel) with global Sea Surface Temperature anomalies as the dependent variable and GISS Stratospheric Aerosol Optical Thickness data (Source ) as the independent variable. The scaling factor determined was 1.431. This equals a global SST anomaly impact of approximately 0.2 deg C for the 1991 Mount Pinatubo eruption. To simplify and standardize the adjustments I’ve applied the same scaling factor to both the observed Sea Surface Temperature data and the model outputs. And I used the same adjustments for all subsets. As you will see, it slightly overcorrects in some instances and under-corrects a little in others. But since the adjustments are the same for the model outputs and instrument-based observations, they have no impact on the trend comparisons.
EAST PACIFIC SEA SURFACE TEMPERATURE COMPARISON
Figure 3 compares the Sea Surface Temperature anomalies of the East Pacific Ocean (90S-90N, 180-80W) to the scaled Sea Surface Temperature anomalies of the NINO3.4 region of the equatorial Pacific (5S-5N, 170W-120W). NINO3.4 Sea Surface Temperature anomalies are a commonly used index of the frequency and magnitude of El Niño and La Niña events, and I’ve scaled them (multiplied them by a factor of 0.22) because the variations in Sea Surface Temperature in that area of the equatorial Pacific are about 4.5 times greater than those of the East Pacific Ocean. As illustrated, the Sea Surface Temperature anomalies of the East Pacific mimic the NINO3.4 Sea Surface Temperature anomalies.
Figure 3
Figure 4 compares the observed Sea Surface Temperature anomalies of the East Pacific to the CMIP3 Multi-Model Mean for the same coordinates. The first thing that stands out is the difference in the year-to-year variability. The observed variations in Sea Surface Temperature due to the ENSO events are much greater than those of the Multi-Model Mean. Keep in mind when viewing the model-observations comparisons in this post that the model mean is the average of all of the ensemble members. And since the variations in the individual ensemble members are basically random, they will smooth out with the averaging. The average, therefore, represents the forced component (from natural and anthropogenic forcings) of the models. And it’s the forced component of the model data we’re interested in illustrating and comparing with the observations in this post, not the big wiggles associated with ENSO.
Figure 4
The difference in the linear trends between the Multi-Model Mean and the observations is also extremely significant. That is the focus of this post. The linear trend of the Multi-Model Mean is 0.114 deg C per decade for the East Pacific Ocean. This means, based on the linear trend of the Multi-Model Mean, that anthropogenic forcings should have raised the East Pacific Sea Surface Temperature anomalies, from pole to pole, by more than 0.34 deg C over the past 30 years. But the observed Sea Surface Temperature anomalies have actually declined. The East Pacific Ocean dataset represents about 33% of the surface area of the global oceans, and the Sea Surface Temperature anomalies there have not risen in response to the forcings of anthropogenic greenhouse gases.
THE REST-OF-THE-WORLD COMPARISON
The Sea Surface Temperature anomalies and Multi-Model Mean for the Rest-Of-The-World (Atlantic, Indian, and West Pacific Oceans) from pole to pole are shown in Figure 5. The linear trend of the multi-model mean shows that the models have overestimated the warming by about 23%.
Figure 5
But even that is misleading, because the observed Sea Surface Temperature anomalies only rose in response to significant El Niño-La Nina events, and during the 9- and 11-year periods between those ENSO events, the observed Sea Surface Temperatures are remarkably flat. This is illustrated first in Figure 6, using the period average Sea Surface Temperature anomalies between the significant El Niño events, and second, in Figure 7, by showing the linear trends of the instrument-based observations data between the 1986/87/88 and 1997/98 El Niño events and between the 1997/98 and 2009/10 El Niño events.
Figure 6
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
Figure 7
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
As you will note, I’ve isolated the significant El Niño events of 1982/83, 1986/87/88, 1997/98, and 2009/10. To accomplish this, I used the NOAA Oceanic Nino Index (ONI) to determine the official months of those El Niño events. There is a 6-month lag between NINO3.4 SST anomalies and the response of the Rest-Of-The-World SST anomalies during the evolution phase of the 1997/98 El Niño. So I lagged the ONI data by six months and deleted the Rest-Of-The-World SST data that corresponded to the 1982/83, 1986/87/88, 1998/98, and 2009/10 El Niño events. All other months of data remain.
Note: The El Niño event of 1982/83 was counteracted by the volcanic eruption of El Chichon, so its apparent role in the long-term warming is minimal.
And what do the climate models show should have taken place during the periods between those ENSO events?
For the period between the 1986/87/88 and the 1997/98 El Niño events, Figure 8, the model mean shows a positive linear trend of 0.044 deg C per decade, while the observed linear trend is negative, at -0.01 deg C per decade. The difference of 0.054 deg C per decade is significant.
Figure 8
The difference between the linear trends is even more significant between the El Niño events of 1997/98 and 2009/10, as shown in Figure 9. The linear trend of the observations is basically flat, while trend of the models is relatively high at 0.16 deg C per decade.
Figure 9
Keep in mind that the model mean, according to the IPCC, represents the anthropogenically forced component of the climate models during the period of 1981 to 2011. Unfortunately for the models, there is no evidence of anthropogenic forcing in the East Pacific Ocean Sea Surface Temperature data or in the Sea Surface Temperature data for the Rest Of The World.
Let’s subdivide the Rest-Of-The-World data even more. This will illustrate why the Sea Surface Temperature anomalies between the significant ENSO events are flat.
THE NORTH ATLANTIC AND THE SOUTH ATLANTIC-INDIAN-WEST PACIFIC SEA SURFACE TEMPERATURE ANOMALY DATA
Figure 10 is a map that shows how the data for the additional discussions were subdivided. Basically, this was done to isolate the North Atlantic from the additional ocean basins in the Rest-Of-The-World data. And the observed Sea Surface Temperature anomalies for those two subsets are shown in Figure 11. As illustrated, the linear trend of the North Atlantic Sea Surface Temperature anomalies is significantly higher than the linear trend of the South Atlantic-Indian-West Pacific subset. This higher trend in the North Atlantic data is caused by the additional mode of natural variability known as the Atlantic Multidecadal Oscillation. And as we will see, the forced component of the models (the model mean) does not account for the additional variability in the North Atlantic attributable to the Atlantic Multidecadal Oscillation.
Figure 10
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
Figure 11
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
Note: The North Atlantic Sea Surface Temperature anomalies for datasets like the Atlantic Multidecadal Oscillation data are normally depicted by the coordinates of 0-70N, 80W-0. Here they include 0-90N, 80W-40E to capture the Mediterranean Sea and corresponding portion of the Arctic Ocean leftover from the other subsets. The additional surface area has little impacton the North Atlantic Sea Surface Temperature anomaly data presented here. But to differentiate it from the other versions of the North Atlantic data, I’ve called it “North Atlantic Plus” in the graphs.
“NORTH ATLANTIC PLUS” COMPARISON
The North Atlantic is the only ocean basin where the models underestimate the long-term trend of the satellite-era Sea Surface Temperature data. See Figure 12. (Also refer to Part 1 and Part 2of an earlier two-part post comparing the Reynolds OI.v2 Sea Surface Temperature dataset to the same CMIP3 Multi-Model Mean, but note that the data in those posts have not been adjusted for volcanic aerosols.) Based on the linear trends, the models have underestimated the warming of the North Atlantic by nearly 35%. Again, the North Atlantic has an additional mode of natural variability called the Atlantic Multidecadal Oscillation or AMO. It seems very obvious that the multi-model mean fails to hindcast and project this additional variability.
Figure 12
And for those interested, I’ve also provided graphs that compare the model mean and observed trends between the significant El Niño events. As shown in Figure 13, the models underestimate the warming that took place between the El Niño events of 1986/87/88 and 1997/98. And as illustrated in Figure 14, the models overestimated the rise in North Atlantic Sea Surface Temperatures between the 1997/98 and 2009/10 El Niño events.
Figure 13
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
Figure 14
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
Let’s take a look at the South Pacific, Indian, and West Pacific comparison. As many of you are aware, I like to save the best for last.
SOUTH ATLANTIC-INDIAN-WEST PACIFIC COMPARISON
Figure 15 compares long-term observed Sea Surface Temperature anomalies and the Multi-Model Mean for the South Atlantic, Indian, and West Pacific Oceans. This is basically the portion of the “Rest-Of-The-World” dataset that is not included in the “North Atlantic Plus” data. As illustrated, the trend of the Multi-Model Mean is about 62% higher than the trend of the observed data. That is, the forced component of the models has over predicted the rise in Sea Surface Temperature anomalies for this subset by a substantial amount.
Figure 15
But the long-term trends are again misleading. The South Atlantic-Indian-West Pacific Sea Surface Temperature anomalies only rise during the significant El Niño events of 1986/87, 1997/98, and 2009/10. Between those events, the Sea Surface Temperature anomalies drop.
Figure 16 compares the observed South Atlantic-Indian-West Pacific Sea Surface Temperature anomalies to the Multi-Model Mean between the 1986/87/88 and 1997/98 El Niño events. The anthropogenic forcings have driven the model-mean upwards during this period, but the linear trend of the observations show that Sea Surface Temperatures declined. And the difference of 0.093 deg C per decade is a major difference. But that’s small compared to the difference between the linear trends of the observations and the model mean for the period between the El Niño events of 1997/98 and 2009/10. That difference is almost 0.18 deg C per decade.
Figure 16
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
Figure 17
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
CLOSING COMMENT
As illustrated in the two earlier posts that use these same datasets (see here and here), the Multi-Model Mean of the CMIP3 coupled ocean-atmosphere climate models do not hindcast and project the Sea Surface Temperature anomalies in any ocean basin, when the data is presented on times-series basis and on a zonal mean (latitude-based) basis. (The model mean of the West Pacific subset may look good on a time-series basis, but not on a zonal mean basis.)
This post confirms the Multi-Model Mean (the forced component of the climate models) does a poor job of hindcasting and projecting the actual rise in global Sea Surface Temperature anomalies, when the data is broken down into two logical subsets: the East Pacific Ocean and the Rest-Of-The-World. The post also illustrates the very basic reasons for that rise.
The models used by the IPCC for their hindcasts and projections assume that anthropogenic greenhouse gases drove the rise in Sea Surface Temperature anomalies from November 1981 to present. This is illustrated by the model mean, which represents the forced component of the models.
But the Sea Surface Temperature anomalies of the East Pacific Ocean (90S-90N, 180-80W) have not risen in 30 years. Refer to Figure 18.
Figure 18
And for the Rest-Of-The-World (90S-90N, 80W-180), Figure 19, the Sea Surface Temperature anomalies only rose during, and in response to, the 1986/87/88, 1997/98, and 2009/10 El Niño events.
Figure 19
There is no evidence that anthropogenic greenhouse gases have had any impact on the East Pacific Sea Surface Temperature anomalies (90S-90N, 180-80W) or on the Sea Surface Temperature anomalies for the Rest Of The World (90S-90N, 80W-180).
ABOUT: Bob Tisdale – Climate Observations
SOURCES
The model mean data is found at the KNMI Climate Explorer Monthly CMIP3+ scenario runs webpage. The Reynolds OI.v2 Sea Surface Temperature anomaly data is available through the NOAA NOMADS website here. And the GISS aerosol optical depth data used to make the adjustments for volcanic aerosols can be found at the Stratospheric Aerosol Optical Thickness webpage, specifically this data.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
The only explanation is, that the “radiative forcings” in the models are just thick arows in K-H diagrams, something of unphysical character, not observed. On the other hand, we have a plenty of natural mechanisms to explain watts have been happening around.
For those who have not noticed, North Atlantic SST peaked around 2006 and now goes at the same rate down. Popcorn times ahead.
Thanks, Anthony.
And happy holidays to all.
Well, the response to that is going to be (with considerable uncertainty) “the anthropogenic heat gets stored up ‘in the pipeline’ somewhere and is ‘released’ during El Nino events” and they would take these graphs as “proof” of that.
I love your straight forward, well illustrated stories, no fudged data, no hype. Wonderful stuff Bob.
Bob – Thank you again for excellent analysis! The logical conclusion as a long time modeller is the GCM assumptions need a good bit of a look. My first step (if I was a GCM person) would be to see how climate sensitivity was handled then do some runs with it as a variable. I suspect that this would show a derived climate sensitivity much closer to that of LC2011 and SB2010 than any of the numbers in AR4. So I am not suprised that I’ve seen no analysis of this sort being done by consensus climate modellers.
I applied the same principle to the North Atlantic, North and Equatorial Pacific and found natural sources of the individual oscillations:
http://www.vukcevic.talktalk.net/PDOc.htm
or to put it simply
http://www.vukcevic.talktalk.net/AP.htm
Of course any climate or oceanographer scientist is free to dismiss it, until all data has been published, but that will happen in due course.
Nice. Thanks, Bob.
Bob,
Could additional GHGs in the air whether natural or not have contributed to the slight cooling in the East Pacific Ocean due to enhanced evaporative cooling caused by more energy in the air?
Apart from that, the failure of that region to warm up despite an active sun, less cloudiness globally and more CO2 could be telling us that the natural mechanisms of equator to pole energy transfer are well capable of changing their speed and capacity to prevent an overall increase in system energy content (when the oceans are included).
I have in mind the speed and size of the water cycle and the latitudinal positions of the permanent climate zones.
I have a bit of a problem with the idea that if you remove the El Niños, the trend of anomaly is flat. A staircase with treads and risers of 12″ each will have a slope of 45° but if you ignore the risers the ‘trend’ would be flat, but I don’t think you could convince many people that that was realistic.
This is all very interesting. But somebody help me out, as I am NOT a climatologist. The question in my mind is: WHY is El Nino step-wise warming a one-way street? Do we actually know what causes the El Nino warming? And if this is a cycle that balances out, what is the mechanism that would reverse the warming associated with El Nino cycles? Why is there no comparable hysteresis apparent in La Nina cycles??
I don’t think it is. For example, in figure 7 you see gradual cooling between events. What I believe happens during the conditions that cause an El Nino is that ocean circulation slows down a little. This allows surface temperatures to rise in places that might not be intuitive but are connected by ocean circulation patterns. Now mind you, that is my own personal speculation. But a El Nino event sees slack trade winds. Ocean circulation is due to winds. Reduced circulation MIGHT mean that the surface gets warmer. Now a La Nina event will directly cool the Eastern Pacific due to increased trade winds but will have less impact on places like the Arctic and the Med. Anyway, I believe it takes a while to get that circulation going again. IF that is true, if we got into a period of persistent La Nina conditions, we should see an increase in circulation patterns and possibly a cooling at the surface. I don’t know, the system is very complex.
Thanks again for another wonderful post, Mr. Tisdale. The graphs are great. Happy Holidays to you, Sir.
In other words, the reduced upwelling off the West coast of South America during an El Nino event might have circulation impacts that manifest in other places.
Bloke down the pub says:
December 19, 2011 at 1:48 pm
“I have a bit of a problem with the idea that if you remove the El Niños, the trend of anomaly is flat. A staircase with treads and risers of 12″ each will have a slope of 45° but if you ignore the risers the ‘trend’ would be flat, but I don’t think you could convince many people that that was realistic.”
Good point. The solution is that the risers are a permanent feature of the stairs, as would be an incremental increase caused by CO2, but no individual El Nino is a permanent feature of the oceans. Taking this point beyond anything Mr. Tisdale said, El Nino look to be causes here and not incremental increases in CO2 concentrations.
@Bloke down the pub and David
The is no rationale behind the assumption that El Nino events cause a trend. For the opposite take on this, that a look at:
http://www.skepticalscience.com/pics/SkepticsvRealistsv3.gif
From this page:
http://www.skepticalscience.com/going-down-the-up-escalator-part-1.html
Could additional GHGs in the air whether natural or not have contributed to the slight cooling in the East Pacific Ocean due to enhanced evaporative cooling caused by more energy in the air?
Stephen, ‘more energy in the air’ , ie higher air temperatures, will cause less evaporative cooling of the oceans.
The ocean surface is on average about 2C warmer than the atmosphere above it and this heat gradient drives heat transfer from the ocean to the atmosphere mostly by evaporation.
David says:
December 19, 2011 at 1:59 pm
But somebody help me out, as I am NOT a climatologist.
I am not either, but here is my simple guide to global warming/cooling anyway.
Oceans!
– There is no large extra heat input from the sun, it oscillates but not to a degree to cause either significant warming or cooling.
– Heat flux up to 30-40 degrees latitude is downwards, there is more heat in then out. Excess energy is taken pole-ward by ocean currents.
– Higher latitudes heat flux is upwards, i.e. more heat out than in, the deficit in heat is supplied by ocean currents from equatorial regions.
Atlantic’s Gulf stream and in the Pacific’s Kuroshio current take heat northwards. Rise in the volume and velocity of these currents takes more heat pole-wards, warming northern seas and lands; result global warming.
http://www.physicalgeography.net/fundamentals/images/oceancurrents.gif
Fall in volume and velocity of the two currents, less heat moved pole-ward, excess heat instead of going north is irradiated in the equatorial regions; result global cooling.
There is similar process in the Southern Hemisphere.
In the Pacific there is also east-west equatorial current system, which is linked to the pole-ward currents system.
There are three major drivers North Atlantic (Gulf stream – the AMO), North Pacific (Kuroshio current- the PDO) and Equatorial Pacific (Equatorial counter current- ENSO). Last two drivers operate a push-pull arrangement, hence synchronisation of the PDO and the ENSO.
http://www.vukcevic.talktalk.net/PDOc.htm
Sun provides the energy, CO2 doesn’t have any significant role to play.
Once the Earth’s axis is tilted sufficiently (Milankovic), the surplus heat taken North is insufficient to stop the Arctic’s excess ice build up; result the Ice age.
Sometime in the near future I shall provide data and explain mechanism of the three drivers mentioned above, till than if you can search for more acceptable hypothesis, if inclined to do so.
David says:
December 19, 2011 at 1:59 pm
“Do we actually know what causes the El Nino warming?”
Declining solar wind speeds: http://omniweb.gsfc.nasa.gov/tmp/images/ret_13923.gif
and volcanic aerosols.
Another useful study. Another brick in the wall of our defences against the gross alarmism pushed by the IPCC. But what a diversion of energy and talent, not just for correcting the shoddy science or hyperbole of that alarmism, but for the fact that it is also an act of rebellion against a powerful and reactionary political establishment! That is wearisome.
I think the reality is that if CO2-alarmism had never been invented, there is nothing at all in the weather of the past 30 years (to pick a time period of particular interest to the alarmists), that would have otherwise been highlighted as astonishing or as a source of unusual concern. And since ‘business as usual’ is not in general a big magnet for the media, we might still have had a decent and civil culture in the baby science of climatology. As it is, we have had a very unpleasant and multiply degrading 20 years or more (maybe the 1988 hearings are a handy marker for the clear onset of the degradation). A recovery path, other than the present generation of climate loud mouths (I cannot bring myself to call them leaders) merely fading into their dotages, is not at all clear to me. The prospect of their suddenly being deprived of their funding and their baubles and accolades does not seem plausible, but that prospect would hold out a tiny glimmer of hope for an earlier progress.
Stephen Wilde says: “Could additional GHGs in the air whether natural or not have contributed to the slight cooling in the East Pacific Ocean due to enhanced evaporative cooling caused by more energy in the air?”
Any answer would be conjecture. Suffice it to say that the Sea Surface Temperature record shows no evidence of an Anthropogenic Greenhouse Gas contribution.
Enjoy your holidays, Stephen.
So there has been no rise in SST of the East Pac in 30 yrs, throw in Antarctica and that’s about 27% of the surface in one slice from north to south. My question is, how has GLOBAL warming managed to jump from 80W to 180W without leaving a trace, is there less CO2 in the atmosphere there? It seems to me that this global warming is based on one period of 20 yrs from 1978 to 1998. Take that out or explain it naturally and the whole theory goes away. I believe that in 1998 the team were saying that natural variability like ENSO was just noise and would be swamped by CO2 but now they are saying that natural variability has managed to flatten the temp trend. Clearly the science of climate is very complicated but as others have pointed out, it’s not about the science, it’s politics.
David says: “WHY is El Nino step-wise warming a one-way street?”
Is it? It has been a one-way street for a few recent decades. However, from the 1940s to the late 1970s, the frequency and magnitudes of El Nino and La Nina events were such that La Nina events dominated by a slight margin. Global surface temperatures did not rise.
You asked, “Do we actually know what causes the El Nino warming?”
Unfortunately, that is an open question and I’d need you to be more specific. But if you’re looking for detailed descriptions of the source of warm water for El Nino events, of how an El Nino forms and then turns into a La Nina, what causes surface temperatures around the globe to vary in response to them, etc., those are covered in the following introduction post…
http://bobtisdale.wordpress.com/2010/08/08/an-introduction-to-enso-amo-and-pdo-%e2%80%93-part-1/
… and in the discussion of ENSO indices (this is one of my favorite posts):
http://bobtisdale.wordpress.com/2011/07/26/enso-indices-do-not-represent-the-process-of-enso-or-its-impact-on-global-temperature/
You asked, “And if this is a cycle that balances out, what is the mechanism that would reverse the warming associated with El Nino cycles?
A multidecadal period when La Nina events truly dominated? Since the 2007/08 ENSO season, La Nina events have outnumbered El Nino events 4 to 2. Is this the start of new period of La Nina domination? Dunno. I’m an observer who’s along for the ride.
You asked, “Why is there no comparable hysteresis apparent in La Nina cycles??”
We haven’t hit a multidecadal period from the 1850s to present (period of instrument temperature record) when La Nina events dominated by a wide margin. Something caused Sea Surface Temperature anomalies to drop significantly from the 1870s until 1910…
http://bobtisdale.files.wordpress.com/2011/12/figure-143.png
…and it wasn’t volcanic eruptions or solar according to the IPCC’s climate models:
http://bobtisdale.files.wordpress.com/2011/12/figure-191.png
You have to keep in mind that, before the 1950s, tropical Pacific Sea Surface source data (the measurements) are sparse enough that the ENSO-related data is sketchy. Before the opening of the Panama Canal in 1914, that data is very sparse and the datasets that infill missing data are presenting lots of assumed data. And tropical Pacific Sea Surface Temperature source data becomes nonexistent as you go further back in time.
“Do we actually know what causes the El Nino warming?”
I will say it probably isn’t the El Nino itself but it manifests after the El Nino. I am going to guess that it is the extreme La Nina conditions that tend to bracket the El Nino.
For example, we had a period from 1990 to about 1995 with positive conditions. As you can see in figure 7, rest of the world ocean temperatures dropped during that time. We had the Great Climate Change of 1976 after a prolonged period of negative conditions. You will notice that after the 1988 El Nino we had a rather deep La Nina event. Then we go back to El Nino conditions for a rather long time and the rest of the world cools off a bit. Then we get the 1998 very large El Nino. The rest of the world begins to cool off as that event falls off but then we go into a rather strong and long La Nina condition that prevents it from cooling off. Then we go to El Nino conditions from about 2003 to 2006 and I believe actually see a very slight cooling trend there.
Now there is one part of this graph in Figure 19 that I believe Mr. Tisdale misses. That is the strong La Nina condition is when the “rest of the world” actually heats up. If you look at figure 19, the trend he shows post-2010 El Nino is actually established BEFORE the 2010 El Nino and is established by the 2008 La Nina.
It is counter-intuitive in some respects but when the Pacific is cooling from La Nina, the ocean is actually GAINING energy. Large El Nino events are often immediately followed by large La Nina events. I believe it is these La Nina events that keep the energy levels up and prevent the temperatures from recovering back to the old trend. The very strong 2008 La Nina that occurred without a preceding very strong El Nino to hide its work reveals what is going on.
The post 2010 trend shown in figure 19 is actually established by the 2008 La Nina BEFORE that El Nino happens. 2009 rest of the world temperatures were already elevated before the 2010 El Nino happened.
During a La Nina event, the Eastern Pacific is cooling but it is also causing a warm anomaly in the Indian, and Western Pacific oceans. The same atmospheric pressure anomalies that cause an increase in trade winds across the Pacific cause a DECREASE in trade winds across the Atlantic. This is one reason why Atlantic tropical storms tend to increase in La Nina years. A La Nina condition often creates the analog of an El Nino condition in the Atlantic. There is reduced trade winds, higher sea surface temperature, lower wind shear conditions and a propensity for storm development. But the energy doesn’t balance because the Pacific is much larger than the Atlantic. If they were exactly the same size, a increase in energy in the Pacific would be balanced by a decrease in energy in the Atlantic and global ocean energy would remain at a net balance though redistributed somewhat.
So in a La Nina year you have: Cool Eastern Pacific with warm Indian and Western Pacific along with a warm Tropical Atlantic (and maybe a cool Northern Atlantic and Southern Atlantic) so Eastern Pacific temperatures drop but the sum of the rest of the world increases.
crosspatch says:
December 19, 2011 at 2:07 pm
WHY is El Nino step-wise warming a one-way street?
“”I don’t think it is. For example, in figure 7 you see gradual cooling between events. What I believe happens during the conditions that cause an El Nino is that ocean circulation slows down a little. (Redacted). Ocean circulation is due to winds. (Redacted). Anyway, I believe it takes a while to get that circulation going again. IF that is true, if we got into a period of persistent La Nina conditions, we should see an increase in circulation patterns and possibly a cooling at the surface. I don’t know, the system is very complex.””
Ocean circulation slows down during El Nino would be right, at least for most of the earths waters, Cooling of the surface during La Nina might be right, but IMHO Ocean circulation is not only due to winds e.g; upwelling, convective heat transfer. I’ve considered Ocean circulation causing La Nina/El Nino switch is due to earths physical black(for that matter white)-body radiation applied to transportation rules. The switch does follow solar radiation, and the variables (currents, volumes, air flow, etc, etc, etc) can be measured, predicatively. Moreover, with known hind-cast (cycles) (600 yr, 60 yr, 11 yr) it would be a very long bow to suggest that SST has anything much to do with CO2.
And that is what my Hero, Bob Tisdale says.