I’ve moved to WordPress. This post can now be found at Multidecadal Changes In Sea Surface Temperature
#########################Longer Title: Do Multidecadal Changes In The Strength And Frequency Of El Niño and La Niña Events Cause Global Sea Surface Temperature Anomalies To Rise And Fall Over Multidecadal Periods?
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UPDATE (November 19, 2010): I’ve added a clarification about the running total of scaled NINO3.4 SST anomalies and its implications. I changed a paragraph after Figure 13, and added a discussion under the heading of “What Does The Running Total Imply?”
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OVERVIEW
This post presents evidence that multidecadal variations in the strength and frequency of El Niño and La Niña events are responsible for the multidecadal changes in Global Sea Surface Temperature (SST) anomalies. It compares running 31-year averages of NINO3.4 SST anomalies (a widely used proxy for the frequency and magnitude of ENSO events) to the 31-year changes in global sea surface temperature anomalies. Also presented is a video that animates the maps of the changes in Global Sea Surface Temperature anomalies over 31-year periods, (maps that are available through the GISS Map-Making web page). That is, the animation begins with the map of the changes in annual SST anomalies from1880 to 1910, and it is followed by maps of the changes from 1881 to 1911, from 1882 to 1912, etc., through 1979 to 2009. The animation of the maps shows two multidecadal periods, both containing what appears to be a persistent El Niño event, one in the early 1900s and one in the late 1900s to present, and between those two epochs, there appears to be a persistent La Niña event.
INTRODUCTION
A long-term (1880 to 2009) graph of Global Surface Temperature anomalies or Global Sea Surface Temperature (SST) anomalies (Figure 1) often initiates blog discussions about the causes of the visible 60-year cycle. The SST anomalies rise from early-1910s to the early-1940s, drop from the early 1940s to the mid-1970s, then rise from the mid-1970s to present. Natural variables like the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO) are cited as the causes for these variations.
http://i51.tinypic.com/119z1ux.jpgFigure 1
Note: HADISST data was used for the long-term SST anomaly graphs in this post. The exception is the GISS SST data, which is a combination of HADISST data before the satellite era and Reynolds OI.v2 SST data from December 1981 to present.
THE PDO CANNOT BE THE CAUSE
The SST anomalies of the North Pacific region used to calculate the PDO are inversely related to the PDO over decadal periods. This was shown in the post An Inverse Relationship Between The PDO And North Pacific SST Anomaly Residuals. This means that the SST anomalies of the North Pacific contribute to the rise in global SST anomalies during decadal periods when the PDO is negative and suppress the rise in global SST anomalies when the PDO is positive. The PDO, therefore, cannot be the cause of the multidecadal rises and falls in global SST anomalies. That leaves the AMO or another variable.
MULTIDECADAL CHANGES IN GLOBAL SST ANOMALIES
If we subtract the annual global SST anomalies in 1880 from the value in 1910, the difference is the change in global SST anomalies over that 31-year span. Using this same simple calculation for the remaining years of the dataset provides a curve that exaggerates the variations in global SST anomalies. This dataset is identified as the “Running Change (31-Year) In Global SST Anomalies” in Figure 2. The data have been centered on the 16th year.
http://i55.tinypic.com/2cndnq1.jpgFigure 2
Why 31 years? A span of 31 years was used because it is approximately one-half the apparent cycle in the datasets, and it should capture the maximum trough-to-peak and peak-to-trough changes that occur as part of the 60-year cycle. Using 31 years also allows the data to be centered on the 16th year, with 15 years before and after.
The curve of the “Running Change (31-Year) In Global SST Anomalies” is very similar to the curve of annual NINO3.4 SST anomalies that have been smoothed with a 31-year filter. Refer to Figure 3. (NINO3.4 SST anomalies are commonly used to illustrate the frequency and magnitude of El Niño and La Niña events. For readers new to the topic of El Niño and La Niña events, refer to the post An Introduction To ENSO, AMO, and PDO – Part 1.) Both datasets are centered on the 16th year. Considering how sparse the SST measurements are for the early source data, the match is actually remarkable at that time.
http://i55.tinypic.com/zmgv9l.jpgFigure 3
Let’s take a closer look at that relationship. The purple curve represents the running 31-year average of annual NINO3.4 SST anomalies, and it shows that, for example, at its peak in 1926, the frequency and magnitude of the El Niño events from 1911 to 1941 were far greater than the frequency and magnitude of La Niña events. The blue curve, on the other hand, portrays the change in global SST anomalies based on a 31-year span, and it shows, at its peak in 1926 that global SST anomalies rose more from 1911 to 1941 than it did during the other 31-year periods in the early 20th century. Skip ahead a few decades to 1960. Both curves reached a low point about then. At 1960, the purple curve indicates the frequency and magnitude of La Niña events from 1945 to 1975 outweighed El Niño events. And over the same period of 1945 to 1975, annual global SST anomalies dropped the greatest amount. Afterwards, the frequency and magnitudes of El Niño events increased (and/or the frequency and magnitude of La Niña events decreased) and the multidecadal changes in global SST anomalies started to rise, eventually reaching their peak around 1991 (the period of 1976 to 2006).
Since Global SST anomalies respond to changes in NINO3.4 SST anomalies, this relationship implies that the strengths and frequencies of El Niño and La Niña events over multidecadal periods cause the multidecadal rises and falls in global sea surface temperatures. In other words, its shows that global sea surface temperatures rose from 1910 to the early 1940s and from the mid-1970s to present because El Niño events dominated ENSO during those periods, and it shows that global sea surface temperatures dropped from the early 1940s to the mid 1970s because La Niña events dominated ENSO.
This apparent relationship contradicts the opinion presented by some climate studies that ENSO is only noise, that ENSO is only responsible for the major year-to-year wiggles in the global SST anomaly curve. Refer back to Figure 1. Examples of these studies are Thompson et al (2009) “Identifying Signatures of Natural Climate Variability in Time Series of Global-Mean Surface Temperature: Methodology and Insights” and Trenberth et al (2002) “Evolution of El Nino–Southern Oscillation and global atmospheric surface temperatures".
Link (with paywall) to Thompson et al (2009):
http://journals.ametsoc.org/doi/abs/10.1175/2009JCLI3089.1
Link to Trenberth et al (2002):
http://www.cgd.ucar.edu/cas/papers/2000JD000298.pdf
Keep in mind, when climate studies such as Thompson et al (2009) and Trenberth et al (2002)attempt to account for El Niño and La Niña events in the global surface temperature record they scale an ENSO proxy, like NINO3.4 SST anomalies, and subtract it from the Global dataset, removing the major wiggles. They then assume the difference, which is a smoother rising curve, is caused by anthropogenic greenhouse gases.
The relationship in Figure 3 (that the multidecadal variations in strength and frequency of ENSO events are responsible for the rises and falls in global sea surface temperature) also contradicts the basic premise behind the hypothesis of anthropogenic global warming, which assumes that the rise in global sea surface temperatures since 1975 could only be caused the increase in anthropogenic greenhouse gases.
The first question that comes to mind: shouldn’t a multidecadal rise in Sea Surface Temperatures require an increase in radiative forcing? The answer is no, and I’ll discuss this later in the post. Back to Figure 3.
Once more, the relationship in Figure 3 illustrates that multidecadal variations in the frequency and magnitude of El Niño and La Niña events cause the multidecadal changes in SST anomalies. But how do I verify that this is the case, and how do I illustrate it for those without science backgrounds? Again, for those who need to brush up on El Niño and La Nina events, refer to the post An Introduction To ENSO, AMO, and PDO – Part 1.
THE ANIMATION OF MULTIDECADAL CHANGES IN SST ANOMALIES
The Goddard Institute of Space Studies (GISS) Global Map-Making webpage allows users to create maps of global SST anomalies and maps of the changes in global SST anomalies (based on local linear trends) over user-specified time intervals. Figure 4 is a sample map of the changes in annual SST anomalies for the 31-year period from 1906 to 1936. In the upper right-hand corner is a value that represents the change in annual SST anomalies over that time span. GISS describes the value as, “Temperature change of a specified mean period over a specified time interval based on local linear trends.” And as far as I can tell, these local linear trends are weighted by latitude. I downloaded the GISS maps of the changes in annual global SST anomalies, starting with the interval of 1880 to 1910 and ending with the interval of 1979 to 2009, with the intent of animating the maps, but the data they presented was also helpful.
http://i56.tinypic.com/21ou8lg.jpgFigure 4
Figure 5 shows the curve presented by the GISS Multidecadal (31-year span) Changes In Global SST anomalies for all those maps, with the data centered on the 16th year. Comparing it to the “Running Change (31-Year) In Global SST Anomalies” data previously calculated, Figure 6, illustrates the similarities between the two curves. The GISS data from the maps presents a much smoother curve.
http://i53.tinypic.com/14j50et.jpgFigure 5
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http://i51.tinypic.com/9hq83s.jpgFigure 6
And if we compare the curve of the GISS Multidecadal (31-year span) Changes In Global SST anomalies from those maps to the NINO3.4 SST anomalies smoothed with a 31-month filter, Figure 7, we can see that the multidecadal changes in Global SST anomalies lag the variations in strengths and magnitudes of ENSO events. The lag prior to 1920 appears excessive, but keep in mind that the early source SST measurements are very sparse. The fact that there are similarities in the curves in those early decades says much about the methods used by researchers to infill all of that missing data.
http://i54.tinypic.com/9gvyh0.jpgFigure 7
THE VIDEO
The animations are presented in two formats in the YouTube video titled “Multidecadal Changes In Global SST Anomalies”. The first format is as presented by GISS, with the Pacific Ocean split at the dateline. That is, the maps are centered on the Atlantic. Refer back to Figure 4. The second format is with the maps rearranged so that the major ocean basins are complete. Those maps are centered on the Pacific. With the maps centered on the Pacific, the animation shows what appear to be two (noisy) multidecadal El Niño events separated by a multidecadal La Niña event.
As noted in the video, the long-term El Niño and La Niña events appear in the patterns, not necessarily along the central and eastern equatorial Pacific. For those not familiar with the SST anomaly patterns associated with ENSO, refer to Figure 8. It is Figure 8 from Trenberth et al (2002) “Evolution of El Nino–Southern Oscillation and global atmospheric surface temperatures". Link to Trenberth et al (2002) was provided earlier.
Figure 8 shows where Sea Surface Temperatures warm and cool during the evolution (the negative lags) of an ENSO event, at the peak of an ENSO event (zero lag), and during the decay of ENSO events (the positive lags). The reds indicate areas that are positively correlated with ENSO events, and the blues are areas that are negatively correlated. That is, the red areas warm during an El Niño and the blues are the areas of that cool during an El Niño. During a La Niña event, the reds indicate areas that cool, and the blues indicate areas that warm.
http://i55.tinypic.com/z1f6o.jpgFigure 8
And for those wondering why the ENSO events don’t always appear along the equatorial Pacific in the animated maps, keep in mind that the maps are showing the multidecadal changes in SST anomalies based on linear trends. The long-term linear trend of the equatorial Pacific SST anomalies are incredibly flat, meaning there is little trend. Refer to Figure 9, which shows the annual NINO3.4 SST anomalies and linear trend from 1900 to 2009.
http://i56.tinypic.com/2ag0u2u.jpgFigure 9
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http://www.youtube.com/watch?v=O_QopFYSyGE
Video 1
And here’s a link to a stand-alone version of the video. The only difference is that the following version includes a detailed introduction, discussion, and conclusion, which are presented in this post. It’s about 5 minutes longer.
http://www.youtube.com/watch?v=SMKA_uG3zK0
Link To Stand-Alone Version Of Video
DOES THE VIDEO AND DATA PRESENT MORE THAN MULTIDECADAL VARIABILITY IN GLOBAL SST ANOMALIES?
Yes. This has actually been stated a number of times, but the following explanation may be helpful.
One of the arguments presented during discussions of multidecadal variations in global SST anomalies is that the Atlantic Multidecadal Oscillation (AMO) is detrended and that it strengthens or counteracts the basic long-term rise in global SST anomalies. However, the data associated with the GISS maps used in the video are based on linear trends. And Figure 7 shows that the Global SST anomalies rose from 1910 to 1944 and from 1976 to 2009 because El Niño events dominated, and dropped from 1945 to 1975 because La Niña events dominated.
That is, the animation of the GISS maps and the data GISS provides with those maps show that the trends in global sea surface temperature are driven by the multidecadal variations in the strengths and magnitudes of El Niño and La Niña events. The “GISS Multidecadal (31-year span) Changes In Global SST anomaly” data peaked in 1931 at 0.39 deg C. Refer back to Figure 5. That is, from 1916 to 1946, global SST anomalies rose 0.39 deg C (based on local linear trends). That equals a linear trend of 0.13 deg C per decade. And the “GISS Multidecadal (31-year span) Changes In Global SST anomaly” data peaked in 1989 at 0.41 deg C, and that equals a trend of 0.137 deg C per decade from 1974 to 2004. Let’s look at the “Raw” Global SST anomaly data. The linear trends of the “Raw” Global SST Anomalies for the same periods, Figure 10, are approximately 0.12 deg C per decade. Again, the peaks in the “GISS Multidecadal (31-year span) Changes In Global SST anomaly” data represent the periods with the greatest linear trends, and, as shown in Figure 7, they lag the peaks of the multidecadal variations in NINO3.4 SST anomalies.
http://i56.tinypic.com/343r903.jpgFigure 10
Note: The highest trend in the later epoch of the GISS-based “change data” is about 5% higher than the highest trend in the earlier warming period. And that’s not unreasonable considering the early period was so poorly sampled. Again, the similarities in trends between the two epochs speaks highly of the methods used by the researchers to infill the data
A NOTE ABOUT THE NORTH ATLANTIC
Oceanic processes such as Atlantic Meridional Overturning Circulation (AMOC) and Thermohaline Circulation (THC) are normally cited as the cause of the additional multidecadal variability of North Atlantic SST anomalies. This additional variability is presented in an index called the Atlantic Multidecadal Oscillation or AMO. The AMO data are simply North Atlantic SST anomalies that have been detrended. As discussed in the post An Introduction To ENSO, AMO, and PDO -- Part 2, the NOAA Earth System Research Laboratory (ESRL) Atlantic Multidecadal Oscillation webpage refers readers to the Wikipedia Atlantic Multidecadal Oscillation webpage for further discussion. And Wikipedia’s description includes the statement, “While there is some support for this mode in models and in historical observations, controversy exists with regard to its amplitude…” The phrase “some support” does not project or instill a high level of confidence.
Early in this post we prepared a dataset that illustrated the “Running Change (31-Year) In Global SST Anomalies” by subtracting the annual SST anomalies of a given year from the SST anomalies 30 years later and repeating this each year for the term of 1880 to 2009. We can prepare the “Running Change (31-Year) In North Atlantic SST Anomalies” using the same simple method. Those two datasets (based on global and North Atlantic SST anomalies) are shown in Figure 11. The “Running Change (31-Year) In North Atlantic SST Anomalies” dataset appears simply to be an exaggerated version of the “Running Change (31-Year) In Global SST Anomalies”.
http://i52.tinypic.com/72yjwj.jpgFigure 11
And comparing the “Running Change (31-Year) In North Atlantic SST Anomalies” to the NINO3.4 SST anomalies smoothed with a 31-year filter, Figure 12, shows that the NINO3.4 SST anomalies lead the multidecadal changes in North Atlantic SST anomalies.
http://i54.tinypic.com/besbvb.jpgFigure 12
Putting Figures 11 and 12 into other words, the AMO appears to simply be the North Atlantic exaggerating the cumulative effects of the variations in the frequency and magnitude of ENSO. During epochs when El Niño events dominate, the SST anomalies of the North Atlantic rise more than the SST anomalies of the other ocean basins, and when La Niña events dominate, the North Atlantic SST anomalies drop more than the SST anomalies for the rest of the globe.
Why? The South Atlantic (not a typo) is the only ocean basin where heat is transported toward the equator (and into the North Atlantic). So warmer-than-normal surface waters in the South Atlantic created by the changes in atmospheric circulation during an El Niño should be transported northward into the North Atlantic (and vice versa for a La Niña). This effect seems to be visible in the animation of Atlantic SST anomalies from September 23, 2009 to November 3, 2010, Animation 1. (Note: By the start of the animation, September 2009, the 2009/10 El Niño was well underway.) Unfortunately, there is a seasonal component in those SST anomaly maps, and it’s difficult to determine whether the seasonal component is enhancing or inhibiting the appearance of northward migration of warm waters. Rephrased as a question, is the seasonal component in the SST anomalies creating (or detracting from) an illusion that makes it appear that the warm SST anomalies are migrating from the South Atlantic to the North Atlantic?
http://i55.tinypic.com/jzbdqe.jpgAnimation 1
The northward migration of warm waters from the South Atlantic to the North Atlantic also appears to be present in the following animation of the correlation of NINO3.4 SST anomalies with Atlantic SST anomalies at time lags that vary from 0 to 12 months, Animation 2. Again the correlation maps show areas that warm (red) or cool (blue) in response to an El Niño and the positive lags represent the number of months following the peak of the El Niño. Three month average NINO3.4 and Atlantic SST anomalies were used.
http://i52.tinypic.com/2gtai6d.jpgAnimation 2
Another reason the North Atlantic exaggerates the effects of ENSO is because the North Atlantic is open to the Arctic Ocean. El Niño events cause increases in seasonal Arctic sea ice melt during the following summer. It would also seem logical that El Niño events would increase the seasonal Greenland glacial melt as well. Refer again to Animation 2. Starting around the 9-month lag, positive correlations (warm waters during an El Niño) migrate south from the southern tip of Greenland, and starting around the 4-month lag from the Davis Strait, along the west coast of Greenland. Is that from glacial ice melt in Greenland and Arctic sea ice melt, with the melt caused by the El Niño? They're correlated with NINO3.4 SST anomalies.
Regardless of the cause, in the North Atlantic, there are significant positive correlations with NINO3.4 SST anomalies 12 months after the peak of the ENSO event, and for at least 6 months after the ENSO event has ended. And this means that the El Niño event is responsible for the persistent warming (or cooling for a La Niña event) in the North Atlantic.
MYTH: EL NIÑO EVENTS ARE COUNTERACTED BY LA NIÑA EVENTS
One of the common misunderstandings about ENSO is that La Niña events are assumed to balance out the effects of El Niño events.
The fact: correlations between NINO3.4 SST anomalies and global sea surface temperatures are basically the same for El Niño and La Niña events; that is, El Niño and La Niña events have similar effects on regional sea surface temperatures; they are simply the opposite sign.
But that does not mean the effects of the El Niño event will be counteracted by the La Niña event that follows. First problem with that logic: La Niña events do not follow every El Niño event. That’s plainly visible in instrument temperature record. Refer to the Oceanic Niño Index (ONI) (ERSST.v3b) table. Also an El Niño event may be followed by a La Niña event that lasts for up to three years. And sometimes there are multiyear El Niño events, like the 1986/87/88 El Niño.
The easiest way the show that La Niña events do not counteract El Niño events is by creating a running total of annual NINO3.4 SST anomalies. If La Niña events counteracted El Niño events, a Running Total would return to zero with each El Niño-La Niña cycle. Refer to the Wikipedia webpage on Running total. The running total of NINO3.4 SST anomalies (to paraphrase the Wikipedia description) is the summation of NINO3.4 SST anomalies which is updated each year when the value of a new annual NINO3.4 SST anomaly is added to the sequence, simply by adding the annual value of the NINO3.4 SST anomaly to the running total each year. I’ve scaled the NINO3.4 SST anomalies by a factor of 0.06 before calculating the running total for the comparison graph in Figure 13.
http://i53.tinypic.com/29fcjl2.jpgFigure 13
And what the Running Total shows is that El Niño and La Niña events do not tend to cancel out one another. There are periods (from 1910s to the 1940s and from the mid 1970s to present) when El Niño events dominated, and a period when La Niña events dominated (from the mid-1940s to the mid-1970s). And with the scaling factor, the running total does a good job of reproducing the global SST anomaly curve. Global temperature anomalies can also be reproduced using monthly NINO3.4 SST anomaly data. This was illustrated and discussed in detail in the post Reproducing Global Temperature Anomalies With Natural Forcings.
UPDATE- The original paragraph has been crossed out and the updated version follows.
Figure 13 appears to imply that 6% of each El Niño and La Niña event remains within the global surface temperature record and that it is this cumulative effect of ENSO events that raises and lowers global Sea Surface Temperatures. Let’s examine that later in the post.
So that’s two ways, using sea surface temperature data, that the multidecadal rises and falls in global sea surface temperatures appear to be responses to the frequency and magnitude of El Niño and La Niña events.
HOW COULD THE OCEANS WARM WITHOUT AN INCREASE IN RADIATIVE FORCING?
Someone is bound to ask, how could the global Sea Surface Temperatures rise over multidecadal periods without an increase in radiative forcing? The answer is rather simple, but it requires a basic understanding of why and how, outside of the central and eastern tropical Pacific, sea surface temperatures rise and fall in response to ENSO events. Refer back to Figure 8, which includes the correlation maps from Trenberth et al (2002), and note that there are areas of the global oceans outside of the central and eastern equatorial Pacific that warm and cool in response to ENSO events. During an El Niño event, the warming outside of the eastern and central equatorial Pacific is greater than the cooling, and global SST anomalies rise.
But why do global SST anomalies rise outside of the eastern and central tropical Pacific during an El Niño event?
There are changes in atmospheric circulation associated with ENSO events, and these changes in atmospheric circulation cause changes in processes that impact surface temperatures. Let’s look at the tropical North Atlantic as an example. Tropical North Atlantic SST anomalies rise during an El Niño event because the trade winds there weaken and there is less evaporation. This is discussed in detail in the paper Wang (2005), "ENSO, Atlantic Climate Variability, And The Walker And Hadley Circulation." Wang (2005) link:
http://www.aoml.noaa.gov/phod/docs/Wang_Hadley_Camera.pdf
Reworded, the reduction in trade wind strength due to the El Niño causes less evaporation, and since there is less evaporation, tropical North Atlantic sea surface temperatures rise. The weaker trade winds also draw less cool water from below the surface. So there are two effects that cause the Sea Surface Temperatures of the tropical North Atlantic to rise during El Niño events. And, of course, the opposite would hold true during La Niña events.
Again for example, during multidecadal periods when El Niño events dominate, the tropical North Atlantic trade winds would be on average weaker than “normal”, there would be less evaporation, less cool subsurface waters would be drawn to the surface, and tropical North Atlantic sea surface temperatures would rise. The western currents of the North Atlantic gyre would spin the warmer water northward. Some of the warm water would be subducted by Atlantic Meridional Overturning Circulation/Thermohaline Circulation, some would be carried by ocean currents into the Arctic Ocean where it would melt sea ice, and the remainder would be spun southward by the North Atlantic gyre toward the tropics so it could be warmed more by the effects of the slower-than-normal trade winds. Similar processes in the tropical South Atlantic also contribute to the warming of the North Atlantic, since ocean currents carry the warmer-than-normal surface waters from the South Atlantic to the North Atlantic.
Refer again to the correlation maps in Figure 8. Those are snapshots of monthly SST anomaly correlations. If those patterns were to persist for three decades due to a prolonged low-intensity El Niño event, global SST anomalies would rise. And the opposite would hold true for a prolonged La Niña event.
Let’s look at the average NINO3.4 SST anomalies during the three epochs of 1910 to 1944, 1945 to 1975, and 1976 to 2009. As shown in Figure 14, the average NINO3.4 SST anomalies were approximately +0.15 deg C from 1910 to 1944; then from 1945 to 1975, they were approximately -0.06 deg C; and from 1976 to 2009, the NINO3.4 SST anomalies were approximately 0.2 deg C. This is a very simple way to show that El Niño events dominated the two periods from 1910 to 1945 and from 1976 to 2009 and that La Niña events dominated from 1945 to 1975.
http://i56.tinypic.com/zxmsg8.jpgFigure 14
Figure 15 compares annual Global SST anomalies to the average NINO3.4 SST anomalies for those three periods. Global SST anomalies rose from 1910 to 1944 because El Niño events dominated, and because the SST anomaly patterns (caused by the changes in atmospheric circulation) associated with El Niño events persisted. Because La Niña events dominated from 1945 to 1975, and because the SST anomaly patterns associated with La Niña events persisted, Global SST anomalies dropped. And Global SST anomalies rose again from 1976 to 2009 because El Niño events dominated, and because the SST anomaly patterns associated with El Niño events persisted.
http://i55.tinypic.com/33cwt4j.jpgFigure 15
The fact that the rise in global Sea Surface Temperature anomalies since the early 1900s can be recreated without an increase in radiative forcing implies a number of things, one being that anthropogenic greenhouse gases do nothing more than cause a little more evaporation from the global oceans.
UPDATE – The following discussion (What Does The Running Total Imply?) has been added.
WHAT DOES THE RUNNING TOTAL IMPLY?
Earlier I wrote, Figure 13 [which was the comparison graph of global SST anomalies versus the running total of scaled NINO3.4 SST anomalies] appears to imply that 6% of each El Niño and La Niña event remains within the global surface temperature record and that it is this cumulative effect of ENSO events that raises and lowers global Sea Surface Temperatures. But is that really the case?
Keep in mind that the running total is a simple way to show the rise in global SST anomalies can be explained by the oceans integrating the effects of ENSO. It does not, of course, explain or encompass many interrelated ENSO-induced processes taking place in each of the ocean basins. Each El Niño and La Niña event is different and the global SST anomalies responses to them are different. For example, the South Atlantic SST anomalies remained relatively flat for almost 20 years, but then there was an unusual warming Of The South Atlantic during 2009/2010. Why? I have not found a paper that explains why South Atlantic SST anomalies can and do remain flat, let alone why there was the unusual rise. In this post, the gif animation of NINO3.4 SST anomaly correlation with North Atlantic SST anomalies, Animation 2, showed that the response of the North Atlantic can persist far longer than the El Niño or La Niña, but if I understand correctly, this type of analysis will emphasize the stronger events. What happens during lesser ENSO events? And there’s the East Indian and West Pacific Ocean. In January 2009, I began illustrating and discussing how the East Indian and West Pacific Oceans (60S-65N, 80E-180 or about 25% of the global ocean surface area) can and does warm in response to El Niño AND La Niña events. The first posts on this cumulative effect were Can El Nino Events Explain All of the Global Warming Since 1976? – Part 1, and Can El Nino Events Explain All of the Global Warming Since 1976? – Part 2. And the most recent post was La Niña Is Not The Opposite Of El Niño – The Videos. The Eastern Pacific Ocean is, of course, dominated by the ENSO signal along the equator. However, because of the North and South Pacific gyres, the East Pacific also influences and is influenced by the West Pacific, which can warm during El Niño and La Niña events. And there’s the Indian Ocean with its own internal variability, represented in part by the Indian Ocean Dipole (IOD). The decadal variability of the IOD has been found to enhance and suppress ENSO, and, one would assume, vice versa.
HOW MUCH OF THE RISE IN GLOBAL TEMPERATURES OVER THE 20TH CENTURY COULD BE EXPLAINED BY THE GLOBAL OCEANS INTEGRATING ENSO?
As shown in Figure 13 and as discussed in detail in the post Reproducing Global Temperature Anomalies With Natural Forcings, virtually all of the rise in global surface temperatures from the early 1900s to present times can be reproduced using NINO3.4 SST anomaly data. The scaled running total of NINO3.4 SST anomalies establishes the base curve and would represent the integration of ENSO outside of the eastern and central equatorial Pacific. Scaled NINO3.4 SST anomalies are overlaid on that curve to represent the direct effects of ENSO on the eastern and central equatorial Pacific. Add to that scaled monthly sunspot data to introduce the 0.1 deg C variations is surface temperature resulting from the solar cycle and add scaled monthly Stratospheric Aerosol Optical Depth data for dips and rebounds due to volcanic eruptions, and global surface temperature anomalies can be reproduced quite well. Refer to Figure 16, which is Figure 8 from the post Reproducing Global Temperature Anomalies With Natural Forcings.
http://i42.tinypic.com/2zqufzp.jpgFigure 16
Basically, that was the entire point of this post. One of the mainstays of the anthropogenic global warming hypothesis is that there are no natural factors that could explain all of the global warming since 1975. But this post has shown that ALL of the rise in global sea surface temperatures since 1900 can be explained by the oceans integrating the effects of ENSO.
CLOSING
This post presented graphs and animations that showed Global SST anomalies rose and fell over the past 100 years in response to the dominant ENSO phase; that is, Global SST anomalies rose over multidecadal periods when and because El Niño events prevailed and they fell over multidecadal periods when and because La Niña events dominated. Basically, it showed that the oceans outside of the central and eastern tropical Pacific integrate the impacts of ENSO, and that it would only require the oceans to accumulate 6% of the annual ENSO signal (Figure13) in order to explain most of the rise in global SST anomalies since 1910. And the post provided an initial explanation as to why and how the global oceans could rise and fall without additional radiative forcings. It also showed that the Atlantic Multidecadal Oscillation (AMO) appears to be an exaggerated response to the dominant multidecadal phase of ENSO. Hopefully, it also dispelled the incorrect assumption that La Niña events tend to cancel out El Niño events.
SOURCES
The HADISST data used in this post is available through the KNMI Climate Explorer:
http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere
The maps used in the video are available from the GISS map-making webpage:
http://data.giss.nasa.gov/gistemp/maps/
39 comments:
Great work. Very well explained and illustrated. Kudos upon kudos!
The clearest explanation yet of ENSO effects.
1) If ENSO "causes" global warming, why has this not been going on for thousands of years? Why has it suddenly started, and when can it be expected to stop? ENSO fails to explain the beginning, or to predict the termination, of the trend.
2) You have shown a correlation, but how do you prove causation? How do you separate the increase in global temperature from a corresponding increase in ENSO strength or frequency, and say that one is the cause of the other, and not vice versa (or that both are artifacts of another process)?
Without physics and mechanisms, this is equivalent to proving that the decrease in pirates is the cause of global warming.
Bob, I suspect you will find the paper by Lee and McPhaden very interesting. They look at the central Pacific and find that SSTs have been increasing during El Ninos but not at other times.
They write "it is the increasing amplitude of El Niño events that causes a net warming trend of SST in the CP region."
www.co2science.org/articles/V13/N46/C1.php
DB
Anonymous: You asked, “If ENSO ‘causes’ global warming, why has this not been going on for thousands of years?”
The assumption in your question is that this process has not been going on for “thousands of years.”
You asked, “Why has it suddenly started, and when can it be expected to stop? ENSO fails to explain the beginning, or to predict the termination, of the trend.”
Again, your question and statement assume that this is a new climatic process.
You asked, “You have shown a correlation, but how do you prove causation?”
This should have been clear in the post and in the graphs. The multidecadal changes in Global SST anomalies lagged the variations in the frequency and magnitude of ENSO events, meaning ENSO leads. The processes (the changes in Hadley and Walker circulation, the teleconnections, etc.) that cause SST anomalies outside of the tropical Pacific to vary in response to ENSO events are well studied and well documented. I provided a link to Wang (2005) in the post and it could serve as a starting point for your studies.
You asked, “How do you separate the increase in global temperature from a corresponding increase in ENSO strength or frequency, and say that one is the cause of the other, and not vice versa (or that both are artifacts of another process)?”
Again, the lead-lag relationship (ENSO leading, with global temperatures responding). Also, NINO3.4 SST anomalies have been incredibly flat since the start of the 20th century. Refer back to Figure 9.
http://i56.tinypic.com/2ag0u2u.jpg
And if you can document the "another process" you're referring to that varies the frequency and magnitude of ENSO events, which, in turn, causes the global oceans to integrate the effects of ENSO and create what we know to be the global sea surface temperature record, feel free to document it all and post it on your blog. Send me a link and I’ll be happy to comment.
And if you feel that Ocean Heat Content somehow alters the strength and frequency of ENSO events, I'll contradict you with the OHC data. There are three posts on this blog that show that the rise in Ocean Heat Content is actually the global oceans responding to ENSO for most ocean basins. A shift in sea level pressure (North Pacific Index) has the greatest impact on the North Pacific, and ENSO, variations in SLP (North Atlantic Oscillation)and the AMO are what drives OHC in the North Atlantic. Those posts use the NODC OHC data, and that's the dataset associated with Levitus et al (2009). All you have to do is divide the global oceans into logical subsets to determine that primary drivers.
You wrote, “Without physics and mechanisms, this is equivalent to proving that the decrease in pirates is the cause of global warming.”
You must be a new visitor to this blog. The mechanisms are well described and documented in a multitude of earlier posts. I elected not to clutter the end of this one with links. If you’d like me to provide you with the links, feel free to ask.
And hasn't the pirate thingy been used elsewhere recently? Originality please.
Anonymous: You asked, “If ENSO ‘causes’ global warming, why has this not been going on for thousands of years?”
The assumption in your question is that this process has not been going on for “thousands of years.”
You asked, “Why has it suddenly started, and when can it be expected to stop? ENSO fails to explain the beginning, or to predict the termination, of the trend.”
Again, your question and statement assume that this is a new climatic process.
You asked, “You have shown a correlation, but how do you prove causation?”
This should have been clear in the post and in the graphs. The multidecadal changes in Global SST anomalies lagged the variations in the frequency and magnitude of ENSO events, meaning ENSO leads. The processes (the changes in Hadley and Walker circulation, the teleconnections, etc.) that cause SST anomalies outside of the tropical Pacific to vary in response to ENSO events are well studied and well documented. I provided a link to Wang (2005) in the post and it could serve as a starting point for your studies.
You asked, “How do you separate the increase in global temperature from a corresponding increase in ENSO strength or frequency, and say that one is the cause of the other, and not vice versa (or that both are artifacts of another process)?”
Again, the lead-lag relationship (ENSO leading, with global temperatures responding). Also, NINO3.4 SST anomalies have been incredibly flat since the start of the 20th century. Refer back to Figure 9.
http://i56.tinypic.com/2ag0u2u.jpg
And if you can document the "another process" you're referring to that varies the frequency and magnitude of ENSO events, which, in turn, causes the global oceans to integrate the effects of ENSO and create what we know to be the global sea surface temperature record, feel free to document it all and post it on your blog. Send me a link and I’ll be happy to comment.
And if you feel that Ocean Heat Content somehow alters the strength and frequency of ENSO events, I'll contradict you with the OHC data. There are three posts on this blog that show that the rise in Ocean Heat Content is actually the global oceans responding to ENSO for most ocean basins. A shift in sea level pressure (North Pacific Index) has the greatest impact on the North Pacific, and ENSO, variations in SLP (North Atlantic Oscillation)and the AMO are what drives OHC in the North Atlantic. Those posts use the NODC OHC data, and that's the dataset associated with Levitus et al (2009). All you have to do is divide the global oceans into logical subsets to determine that primary drivers.
You wrote, “Without physics and mechanisms, this is equivalent to proving that the decrease in pirates is the cause of global warming.”
You must be a new visitor to this blog. The mechanisms are well described and documented in a multitude of earlier posts. I elected not to clutter the end of this one with links. If you’d like me to provide you with the links, feel free to ask.
And hasn't the pirate thingy been used elsewhere recently? Originality please.
DB: Thanks for the link to Lee and McPhaden (2010), but I beat you to the punch on that one. Here's a link to my comments:
http://bobtisdale.blogspot.com/2010/08/on-lee-and-mcphaden-2010-increasing.html
Regards
"Thanks for the link to Lee and McPhaden (2010), but I beat you to the punch on that one."
Ah, I missed that one. I guess that's what happens when you go on vacation in August.
DB
“Natural variables like the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO) are cited as the causes for these variations.”
----------------
My take on this statement is that part of the reason for the mis-application of causation stems from the areal misrepresentation of the maps usually used, for example, the Figure 4 map of the post. The equatorial Pacific Ocean is a much larger area than either the N. Pacific or the N. Atlantic so intuitively I think the larger area ought to impact the smaller areas. Not only is the EQ. Pacific larger but it also receives a more constant and intense solar input.
Could it be that those championing the PDO or the AMO have an interest in their favorite ocean being of recognized importance in the scheme of things?
Thanks for the effort and also the internal links. I had to go re-read a few things.
Hi Bob,
While I continue commend you for the great amount time and effort you put into your research work, it's probably no surprise that I don't agree with your position here.
In your opinion, which event comes always comes first, changes in the strength and frequency of ENSO or atmospheric chemical, physical, and general circulation changes, possibly through some external above-ground, forcing parameter? While there are times that ENSO can be a main driver, there are times and events when I see the changes happening the other way around through independent and unrelated, external forcing agents. Are the cyclical features of ENSO always a major causation agent like you are suggesting here, or can they also be a response to some external forcing that can create changes in another media (e.g., the atmosphere) first before it ever reaches or effects the ocean?
Let's just use for an example an external force outside of the internal ENSO cycle forces, such as a significant increase in volcanic activity, that creates an increase in particulate matter in the atmosphere that leads to a decrease in global atmospheric and oceanic temperatures in the short-term. Then as the particulate matter decreases in the atmosphere over a relatively short-period of time but a significant amount of greenhouse gases emitted by the significant volcanic activity remains in the atmosphere and ultimately causes global atmospheric and oceanic temperatures to gradually increase. In this case, the atmospheric changes and responses appear to have occurred first before any ocean temperature effects were likely noted through many times in the recent and distant past.
Is your conclusion, based on this new analysis, that the changes in the long-term ENSO cyclical pattern and the noted global atmospheric and oceanic temperature changes over that same time could actually cause an increase in volcanic activity that ultimately produces those changes in the atmospheric chemistry and particulate matter and that the resultant changes in the cyclical decrease and eventual increase in atmospheric and oceanic temperatures? Because if you feel that changes in the strength and frequency of ENSO is the ultimate driver of oceanic and atmospheric temperatures over time, you appear to be saying that those same changes in strength and frequency of ENSO actually initiated the increase in the volcanic activity, which we know is not a very reasonable conclusion based on historical records and known geological events.
If however, you agree that ENSO and oceanic and atmospheric temperatures are actually affected by an increase in volcanic activity both in the short-term (increase in atmospheric particulates) and long-term (increase in atmospheric greenhouse gases), is it not unreasonable to conclude that the ENSO cycles are also affected by similar changes in the atmosphere due to an increase in man made pollution just like the response you see with the atmospheric pollution from the natural volcanic activity? After all, the particulates and gases from both types of external sources (volcanic activity and manmade) are the same and the atmospheric and oceanic (ENSO) responses to both should also be the same. There is nothing special about either pollution source.
Therefore, the changes in the strength and frequency of ENSO can be a response to those example external (highly independent) forces and not necessarily the other way around in all (natural) cases like you are trying to postulate here.
Dennis H.
I don't "champion" the PDO and AMO, I am just an independent physicist who knows the "consensus" touted to the public is broadly incompetent, and not just in climate science. Like you, I just want to cut through to the heart of things. So I note without championing that
htt://www.appinsys.com/globalwarming/pdo_amp.htm
shows a graph, apparently by Joe D'Aleo, comparing U.S. temperatures vs. PDO + AMO, that seems to show these two together govern those particular temperatures, over the period 1905 to 2000, with an R-square value of 0.85. Make of it what you will, I am just learning.
Supposing all you have written is correct, there is still the question of the overall trend in the data of 0.4 - 0.5 ºC temperature increase per century. Do you know of any definite data indicating whether the trend is due to a recovery from the Little Ice Age, or more fundamentally, just an increase in the relevant activity of the Sun in the last hundred and some years, or what (previously unknown, massive undersea volcanic eruptions, perhaps -- a joke, I'm joking, aaah, don't hit)? (If it's the latter, there is always someone to say, "the Sun is out of control", but if the former -- if people can agree that past solar activity caused the Little Ice Age, and the Medieval Warm period before that -- it's just the climate system returning to "normal" after an extended cool period, after an extended warm period -- just cycles around a mean). Science needs to cast off apocalyptic "explanations" (like the runaway "greenhouse effect"), they are juvenile fantasies.
Harry Dale Huffman: I Have a canned reply for each time Joe D'Aleo's AMO+PDO graph appears in a post at WUWT. It reads:
Unfortunately, the PDO and AMO are not similar datasets and cannot be added or averaged. The AMO is created by detrending North Atlantic SST anomalies, while the PDO is the product of a principal component analysis North Pacific SST anomalies, north of 20N. Basically, the PDO represents the pattern of the North Pacific SST anomalies that are similar to those created by El Niño and La Niña events. If one were to detrend the SST anomalies of the North Pacific, north of 20N, and compare it to the PDO, the two curves (smoothed with a 121-month filter) appear to be inversely related:
http://i52.tinypic.com/fvi92b.jpg
I’ll have to update the discussion of this in the Introduction to the PDO post:
http://bobtisdale.blogspot.com/2010/09/introduction-to-enso-amo-and-pdo-part-3.html
###
And you asked, "Supposing all you have written is correct, there is still the question of the overall trend in the data of 0.4 - 0.5 ºC temperature increase per century. Do you know of any definite data indicating whether the trend is due to..."
I have found nothing certain. It's one of the topics that's still debated by many. But this post does explain trend, not only multdecedal variability.
Hi Dennis: No surprise that you do not agree.
You wrote, "If however, you agree that ENSO and oceanic and atmospheric temperatures are actually affected by an increase in volcanic activity both in the short-term (increase in atmospheric particulates)..."
Much of this post dealt with the multidecadal frequency and magnitude of ENSO events. Where did I write that the multidecadal variations in the frequency and magnitude of ENSO events were impacted by volcanic aerosols? I didn't.
You asked, “In your opinion, which event comes always comes first, changes in the strength and frequency of ENSO or atmospheric chemical, physical, and general circulation changes, possibly through some external above-ground, forcing parameter?”
There is no doubt that volcanic aerosols can outweigh the impact of a major El Niño event. El Chichon and the El Niño of 1982/83 are an prime example. However, there is no evidence that a major volcanic eruption suppresses the ENSO event itself, just its effects om atmospheric circulation. And there is no evidence that suggests that volcanic aerosols suppress the frequency and magnitude of later ENSO events. In fact, to the contrary, if memory serves me well, there’s a paper with Mann as one of the authors that notes a major El Niño event follows a major volcanic eruption within 5 to 6 years, but there was little confidence expressed by the authors in their results.
You concluded, “Therefore, the changes in the strength and frequency of ENSO can be a response to those example external (highly independent) forces and not necessarily the other way around in all (natural) cases like you are trying to postulate here.”
All of your speculation and supposition does not appear to be supported by data. Did the 1982 and 1991 eruptions of El Chichon and Mount Pinatubo suppress the strength and frequency of El Niño events in the latter part of the 20th century, Dennis?
John F. Hultquist said, "Could it be that those championing the PDO or the AMO have an interest in their favorite ocean being of recognized importance in the scheme of things?"
And some bi-oceanic people want to combine the AMO and PDO. When favored explanations don't hold up to closer scrutiny, some people can become quite angry with the people who present the evidence to the contrary. Just ask Leif Svalgaard.
Bob,
In reply to your question:
"Did the 1982 and 1991 eruptions of El Chichon and Mount Pinatubo suppress the strength and frequency of El Niño events in the latter part of the 20th century"
Here is a web link from the fellow skeptic info web site, ICECAP:
http://icecap.us/images/uploads/Volcanism_and_Climate.pdf
That ICECAP story on volcanism and climate response stated the following:
"Volcanic eruptions can override El Nino warming. The volcanic cooling associated with the major eruptions in 1982 and 1991 were able to minimize and then offset the warming with the super El Nino of 1982/83 and the El Ninos of the early 1990s on a global basis."
So in effect, the atmospheric response was able to minimize (or enhance) the effects of the peaks (or valleys) of the ENSO cycles.
Again the response to the volcanoes (or any similar pollution source) occurred in the atmosphere first and not the other way around. ENSO does not initiate the atmospheric response to the volcanoes or other similar (manmade) atmospheric pollution sources as you are suggesting. The ocean ENSO response occurs after the changes already occurred in the atmosphere due to the interaction of those pollution sources, whose cycles or forcings are independent of the ENSO cycles.
Dennis H.
Dennis: Again, I confirmed that the effects of volcanic eruptions can outweigh the effects of El Nino events. But there is no evidence that volcanic eruptions alter the frequency and magnitude of ENSO events. There is a significant difference.
Bob,
Here is another link on the effects on volcanism and the atmospheric response:
http://www.global-climate-change.org.uk/2-6-3.php
The last paragraph in that link states the following: "Volcanic activity has the ability to affect global climate on still longer time scales. Over periods of millions or even tens of millions of years, increased volcanic activity can emit enormous volumes of greenhouse gases, with the potential of substantial global warming (Pickering & Owen, 1994; Rampino & Volk, 1988). However, the global cooling effects of sulphur dioxide emissions (Officer & Drake, 1983) will act to counter the greenhouse warming, and the resultant climate changes remain uncertain. Much will depend upon the nature of volcanic activity. Basaltic outpourings release far less sulphur dioxide and ash, proportionally, than do the more explosive (silicic) eruptions."
Over the past 100 years or so, our manmade sources of the same pollutants show a continued increase in greenhouse gases (GHG's) while the amount of the regulated criteria pollutants, like the GHG countering SO2 emissions, have been greatly reduced in the atmosphere due to the passage of the Clean Air Act in 1970. The end result since then is there has been a reduced countering effect of the GHG's of these manmade pollutants, and thus the noted increase in global temperatures. This is all independent of the natural ENSO cycles and thus may be influencing those same ENSO cycles by how much solar radiation is reaching the ocean surface through chemistry and general atmospheric circulation pattern changes.
Dennis H.
Dear Bob,
The analysis of the running total of Nino 3.4 SSTs is fascinating.
One question: does it work for other SST data sets (and averaging periods), or is it something special in HadISST or your choice of anomaly period?
I ask because 1950-79 seems a strange choice for a base year and HadISST is a unique statistical analysis of the available data.
Cheers,
Nebuchadnezzar
Dennis: First: I'm not discussing epochs of millions of years, just 130 years. And I'm presenting evidence that the oceans integrate ENSO. It's never been presented or discussed in a paper, yet.
Also, are we dealing with the same levels of CO2, etc.? You may not be comapraing apples to apples.
Nebuchadnezzar: The simple integral (running total) of NINO3.4 SST anomalies also works with HADSST2 and, of course, with the Trenberth and Stepaniak NINO3.4 SST anomaly data since its based on HADSST2.
And, not to worry, in the event that the Hadley Centre elects to change their methods for HADSST3, lets say by not reinserting the sampled data back into the interpolated data, the NINO3.4 SST anomalies as they exist now can be easily reproduced from ICOADS data.
Regards
Thanks Bob,
And the base period? I guess that might change things a little.
Nebuchadnezzar
Nebuchadnezzar: Regarding the base years, I discovered the effect using the Trenberth and Stepaniak NINO3.4 data. I was trying to determine if La Nina events cancelled out El Nino events, as is widely believed. Their use of 1950-1979 base years was discussed in Trenberth (1997) "The Definition of El Nino":
ftp://grads.iges.org/pub/kjin/BADGER/1021/Trenberth-1997-BAMS(ElNino.Define).pdf
Trenberth writes, "Figure 1 shows the 5-month running mean SST time series for the Niño 3 and 3.4 regions relative to a base period climatology of 1950–79 given in Table 1. The base period can make a difference. This standard 30-year base period is chosen as it is representative of the record this century, whereas the period after 1979 has been biased warm and dominated by El Niño events (Trenberth and Hoar 1996a)."
There's no reason for me to hide that the base years are necessary for the running total to recreate the global temperature anomaly curve. In fact, I'm sure someone could write a program that could find more ideal base years.
The Hadley Centre could use the concept of the oceans integrating ENSO to verify what periods need to be reexamined. For example, the 1945 discontinuity wouldn't appear so out of place if the peak around 1943/44 didn't exist. But the spike in 1943/44, which is most prevalent in the Indian Ocean, exists in areas that are well sampled. Is it justifiable there? Could it be an aftereffect of the three year El Nino that came before it? That would be a lot of warm water released to the surface.
Nebuchadnezzar: A follow up to my earlier reply regarding base years: IMO, selecting the proper base years so that the running total reproduces the underlying global temperature anomaly curve makes more sense that rearranging manufactured aerosol datasets in climate models to recreate the mid-century flattening of the curve.
Sir,
Maybe you can use these:
http://www.dmi.dk/dmi/index/klima/klimaet_indtil_nu/temperaturen_i_groenland.htm
http://met.no/?module=Articles;action=Article.publicShow;ID=882
Best regards
Thanks Bob,
I can see that the grounds for choosing that period sound sensible; it is in Trenberth's words "representative of the 20th century".
However, if you did use the whole twentieth century (1901-2000 or similar) it wouldn't just be representative of the 20th century, it would actually be the 20th century. If you did this, the running total would come out as zero, wouldn't it?
It's certainly interesting that it comes out looking like the global average if you choose the base-period just right, but I guess I'm left wondering, what's really so special about the period 1950-79?
Thank you for this exciting post. I reconstructed your operations and got the same result. Anyway... I have some maybe helpful suggestions. The 31-year SST-difference makes some sense, anyway it's some kind of "constructed". I calculated the yearly difference between NH (extratropics) and SH (also extratropics) in GISS data and the resuling series is very similar to the AMO (look http://www.dh7fb.de/reko/dtnhsh ). After generating a plot with this difference (I called it "HMO" with H for hemispheric) and the global-series from GISS you can see, that almost all warming in the last 30 years comes from the NH. See http://www.dh7fb.de/reko/ensogiss . In green is marked the 30 years running Mean of ENSO 3.4 temps after transforming the record 15 years into the future. The correlation is R= 0.62 between the unsmoothed series of "HMO" and the 15y- transformed record of 30 y running Mean of the Nino 3.4 .So it could be, that the global temperatures are controlled by the ENSO-Mean with a timelag of about 15 years.
best wishes!
Frank
What is the justification for assuming that, when "integrating" the ENSO events, that the mean of all the data should be non-zero? Without the constant non zero mean, no trend would emerge in the data to mimic the long term of the global SST.
Indeed, shouldn't one try and determine ENSO conditions long before the instrumental record, average to the present, and then integrate? Would not that make more sense? Indeed, if you did that you could still possibly get a trend in the last 150 years, but no trend over a record the length of a hypothetical ENSO record from pre-instrumental times.
Here's a thought, instead of integrating ENSO, differentiate the global SST's and compare that to ENSO. This is a comparison which is essentially mathematically equivalent, and avoids pesky arbitrary constant terms.
I guess I missed it, but what drives these oscillations?
My apologies to all for the delay in moderating and replying to the comments.
Anonymous (November 21, 2010 4:57 AM): Thank you for the links. (I used google to translate them. Thank you, google.) Anthony Watts at wattsupwiththat would be interested in the link to the discussion on surface station locations.
Anonymous (November 21, 2010 7:21 AM): You asked, “I guess I'm left wondering, what's really so special about the period 1950-79?”
It seems only to establish the right ratio of positive to negative anomalies, and that ratio allows the running total to reproduce the global temperature anomaly curve. We can also shift NINO3.4 data of other base years until the right ratio is established.
Frank: Thanks for the discussion about “hemispheric dipole”. Regarding your graph, the lag (or divergence) that seems to work its way into the data in the 1960s could be the result of the Southern Ocean SST data. It’s really just the climatology (basically a noisy flat line) before 1960s then it rises and plateaus and then falls again in the 1990s.
Andrew: You concluded your questions with, “Here's a thought, instead of integrating ENSO, differentiate the global SST's and compare that to ENSO. This is a comparison which is essentially mathematically equivalent, and avoids pesky arbitrary constant terms.”
I’ll do that in a follow-up to this post. Thanks. In the mean time, here’s a graph from a very early post that compares the annual change in HADCRUT3GL and the Trenberth NINO3.4 SST anomalies that have been scaled.
http://i30.tinypic.com/15rl7qo.jpg
sykes.1: You asked, “I guess I missed it, but what drives these oscillations?”
Assuming you’re asking about ENSO (El Niño and La Niña events), that’s one of the unanswered questions in climate science. A relaxation of the Pacific trade winds initiates an El Niño event, and a La Niña event typically follows an El Niño event as the Pacific tries to return to a “normal” state. But there are many factors that can cause the trade winds to relax, and there are many factors that can cause the strengths of individual ENSO events to be different. In fact, the general thought is that each ENSO event is subtly different as are the global responses. And that’s one of the reasons that climate modelers have very little luck trying to reproduce the ENSO record of the 20th century. Sorry I couldn’t give you a definite answer.
Andrew said "Here's a thought, instead of integrating ENSO, differentiate the global SST's and compare that to ENSO. This is a comparison which is essentially mathematically equivalent, and avoids pesky arbitrary constant terms."
The pesky arbitrary constant is the interesting thing that makes the integrated series look like the global temperature record.
If you differentiate the global temperature record then it's almost certain to look like the ENSO time series because this is the strongest mode of year to year variability.
What Bob's saying that's interesting and perhaps controversial is that global temperature change can be almost completely explained by the integrated Nino time series. That's why I'm worried about the choice of base years. Bob's justification seems to be that it's the right period to use because it gives the right answer, which just leads us round in circles.
Nebuchadnezzar
Nebuchadnezzar says: “Bob's justification seems to be that it's the right period to use because it gives the right answer, which just leads us round in circles.”
The base years of 1950-1979 are only required to make the running total work. The curve of the 31-year average NINO3.4 SST anomalies used for the comparisons to multidecadal changes in SST anomalies in Figures 3, 7, and 12 is not dependent on base years. And the years portrayed by each map (not the base years) are the only selection made for the maps of the multidecadal changes in SST anomalies used in the video.
Regardless, adjusting or selecting data to provide the right answer is commonplace in the present state of climate science. GISS admitted that the Lean (2000) TSI reconstruction was obsolete but used it anyway to help recreate the rise in the early 20th century global temperatures. The Hoyt and Schatten TSI reconstruction was prepared specifically for the same reason, so that it explained the rise in the global temperature in the early 20th century. I recall discussions about how the aerosol datasets being used by climate modelers were prepared only to explain the mid-century dip in global temperatures. There are a multitude of adjustments made to climate models so that the output meets the modeler’s expectations.
The concepts and bases for them are not dependent the running total. What I’ve shown in a number of past posts is that the East Indian and West Pacific Oceans are warmed by El Niño and La Niña events and that the warmings are cumulative. In an earlier and this post I’ve shown that the ENSO signal persists in the North Atlantic for a number of reasons and that this may explain the additional variability of the AMO. And in this post I’ve shown, because of these ENSO-induced processes, that ENSO COULD explain all (or part) of the rise in global temperatures from the early 1900s to present.
Regards
Andrew and Nebuchadnezzar: In addition to a graph of NINO3.4 SST anomalies and the first derivative of global SST's, what other specifics do you want from the comparison--correlation?
Bob-I tend to think that it never hurts to include all the information one can get, but It's your blog, it's up to you. :)
Anyway, thanks for the graph of the SST derivative. As I thought, the ENSO and it are clearly very similar in their behavior.
It's clear that the ENSO events definitely have long term impacts. You seem to be the only one even trying to develop models of that effect, so kudos there. Just offering some advice on there construction, makes me feel like an important participant. :)
"If you differentiate the global temperature record then it's almost certain to look like the ENSO time series because this is the strongest mode of year to year variability."
It does, and this is an interesting statement.
1. SST'=ENSO
2. Obviously the integral of SST'=SST
3. then from 1 and 2 SST=integral of ENSO
lgl-Actually, you calculus is a little off my friend. it's more like:
1. d/dt SST ∝ ENSO
2. the integral of d/dt is equal to the SST by the fundamental theorem of calculus
3. There fore, the integral of ENSO is proportional to SST
Andrew,
But just a little. "It is very likely that most of the temperature increase the last century was caused by ENSO"
And of course there is the offset of around 0.00025 on the SST' so,
1. d/dt SST = 0.011*ENSO+0.00025
3. SST = 0.011*(integral of ENSO) + 0.00025t, where t is months since 1880.
How much off this time Andrew?
This is brilliant!!! And this matches exactly what I've been looking at using the NOI data (SST for EL nino region 3.4) from NOAA (available since 1950). Namely, what struck me is that since the el nino from 1958, each peaking el nino thereafter has been stronger than the previous one, until the 1997/1998 el nino:
1958 1.7
1973 2.1
1983 2.3
1998 2.5
(2010 1.8: trend reversal! see below)
Doing simple linear regression; the la nina peaks from 1958 to 1998 produce a slope (increase) of 0.0017/month with an R2 of 0.97.
That said, looking at la ninas since the 1950s; these increased in strength until the one in 1974:
1950 -1.7
1956 -2.0
1974 -2.1
and have since then decreased (the peak la ninas that is) until the most recent one in 2008:
1974 -2.1
1989 -1.9
2000 -1.6
2008 -1.4
Interestingly, the decrease in la nina peaks from 1974 to 2008 is also 0.0017/month with an R2 of 0.97.
I only picked the strongest consecutive enso events since the others can be regarded as "noise".
The fact that both the el nino and la nina peaks increased and decreased, respectively, with the exact same slope make me believe there is an underlying mechanism that causes this: the pacific decadal oscillation (PDO).
Adding PDO events (warm to cold reversals, vice versa, phase shifts, etc) to the NOI data we instantly see the following events coincide:
The 2008 la nina coincides exactly with the PDO GPTC.
The 1998 el nino coincides exactly with the PDO phase shift from warm to cold.
The 1988 la nina coincides exactly with the highest PDO (LPTC) since 1934.
The 1977/78 el nino coincides exactly with the PDO phase shift from cold to warm.
The 68/69 la nina coincides exactly with PDO's phase reversal. The 55/56 la nina coincides exactly with the lowest PDO value since 1900.
Note: the PDO cycle is exactly related to the sun's orbital motion (torque) cycle.
Apparently not all enso events coincide with all significant PDO changes, but the key (peak) events do, and thus it can be deducted that the enso cycle, therefore, also coincides with the sun's orbital motion (torque) cycle.
In addition, between 1950 and 1977 there were 126 la nina seasons (months) and 75 el nino seasons: PDO was cold.
Between 1977 and 1998 there were 53 el nino seasons and 27 la nina seasons: PDO was warm.
Hence, it is obvious that the enso cycle is highly correlated with the PDO, which in turn is highly correlated to the sun's torque cycle. This has been confirmed by Dr Theodor Landscheidt! In addition, it appears to me that we've entered a trend reversal in enso strength; going from a el nino dominated 40 yr period that ended in 1998 to a la nina period of several decades that started in 2008.
All this also coincides exactly with the climate change we've experienced since 1977 (when the PDO shifted from cold to warm, ending in 1998 when the PDO shifted from warm to cold: in 1998 the highest global temperatures have been recorded and have since not been broken... 2010 may become the highest on record but only, in my opinion due to the 2009/2010 el nino we've experienced). Subtract the effect of the el nino and it won't be the highest or 2nd highest temperature, but even lower....
Now if global temperatures continue to rise, while we continue to be in the PDO cold phase that peaked in 2007 and will last till 2016, that's when anthropogenic climate change is real, to me!
references:
PDO: http://jisao.washington.edu/pdo/
PDO and Solar torque cycle: Trends in Pacific Decadal Oscillation
Subjected To Solar Forcing: http://www.john-daly.com/theodor/pdotrend.htm
Solar Activity Controls El Niño and La Niña: http://www.john-daly.com/sun-enso/sun-enso.htm
global atmospheric temp trends: http://www.drroyspencer.com/2010/11/oct-2010-uah-global-temperature-update-0-42-deg-c/
lgl-Your math looks good to me :)
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