UPDATE July 2, 2011: I’ve modified the wording of the second paragraph after Figure 4.
INTRODUCTION
I’ve written numerous posts that describe the Pacific Decadal Oscillation (PDO), what the PDO represents, and, just as important, what it does not represent. For those new to the PDO and for those needing a refresher, refer to An Introduction To ENSO, AMO, and PDO — Part 3.
IceCap recently published a post about the PDO. One of the illustrations in that post confirms a point I have been making: that the PDO does not represent the Sea Surface Temperatures of the North Pacific. And I’ve added a few additional comments and clarifications about the IceCap post.
In my post An Introduction To ENSO, AMO, and PDO — Part 3, the discussions of the PDO patternwere about the spatial pattern. But the word pattern can also be time-related and, therefore, it could pertain to the PDO’s “behavior in time”. A recent discussion on a blog thread gave me the impression that the multiple meanings of the word pattern could be the cause of some of the confusion about the PDO.
Also, much of the post An Introduction To ENSO, AMO, and PDO — Part 3discussed and illustrated the fact that the PDO does not represent the Sea Surface Temperature Anomalies of the North Pacific. There is another factor that may lead to some of the continued misunderstandings about the PDO. The PDO data is standardized. This could greatly exaggerate the magnitude of its variations. Could the standardization also inflate its perceived importance?
I had also wanted to include the errors in the SkepticalScience post It’s Pacific Decadal Oscillation . The SkepticalScience post was obviously written by someone who never plotted the Sea Surface Temperature anomalies of the North Pacific, who misunderstands how the PDO is calculated and what it represents, and who misunderstands or elects to misrepresent climate oscillations. But this post is long, so I’ll present the Skeptical Science errors in a separate post.
THE ICECAP PDO POST
Figure 1 is a screen cap of the opening of Joe D’Aleo’s post about the PDO at IceCap. I’ve included the screen cap because if you were to click on the post title Is the PDO real or a skeptic inventionat IceCap the link does not bring you to the post; it links to a .pdf document titled “THE PDO.” Most of the IceCap post and the linked .pdf document appear to be the same, but their opening paragraphs and the titles are different.
Figure 1
That aside, most of the IceCap post is intended to confirm the existence of the PDO, which is something I don’t dispute. If you’ve watched any of the SST .gif animations or videos I’ve prepared, the positive and negative PDO spatial patterns are very visible. And they should be; the PDO spatial pattern is the most prevalent of the many that form in the North Pacific SST anomalies. The IceCap post also mentions using the Pacific Decadal Oscillation in weather forecasts. Since there are a number of papers that describe weather patterns associated with the PDO, I imagine the PDO data is a useful index for meteorologists.
But one of the points that I have illustrated and discussed a number of times is that the PDO does not represent the Sea Surface Temperature anomalies of the North Pacific, north of 20N. The IceCap post includes a group of PDO- and ENSO-related maps, Figure 2. And those maps actually illustrate that the PDO does not represent the Sea Surface Temperature (SST) anomalies of the North Pacific.
Figure 2
I’ve modified the illustration, Figure 3, by highlighting the area used to calculate the PDO data and by covering the rest of the maps with text. The PDO is not calculated from the SST data south of 20N, so all of that additional visual information exaggerates the surface area represented by the PDO.
Figure 3
My text in Figure 3 reads: In The Positive (Warm) Phase Map Of The PDO Shown Above Left, The Sea Surface Temperature Anomaly For The North Pacific North Of 20N Appears To Be Negative. That Is, The Negative SST Anomalies Cover A Greater Surface Area And They Are More Intense Than The Positive Anomalies. The Opposite Holds True For The Map On The Right-Hand Side. How Then Could A Positive (Warm) Phase Of The PDO Raise Global Surface Temperatures, And Vice Versa?
Someone is bound to note that the IceCap post does not mention that the PDO has an impact on Global surface temperatures. Agreed. Their post doesn’t. This part of my discussion is about the common belief that the sign of the PDO dictates whether global temperatures rise or fall. Since the sign of the PDO does not represent the Sea Surface Temperature of the North Pacific the belief is unfounded.
In past posts, I’ve presented that there is an inverse relationship between the PDO and the Sea Surface Temperature (SST) Anomalies of the North Pacific. This can be shown with a graph that compares the PDO data and the difference between the SST anomalies of the North Pacific north of 20N and global SST anomalies. For simplicity sake, we’ll use the term “North Pacific Residual” for the data that’s calculated as the North Pacific SST anomalies minus the Global SST anomalies. Refer to Figure 4. We’ll use the North Pacific Residual in the comparison graph because one of the steps taken to calculate the PDO is to subtract Global SST anomalies from the SST anomalies of each 5 degree by 5 degree grid of the North Pacific north of 20N. Both datasets in Figure 4 have been smoothed with 121-month running average filters. Other than the agreement between the multidecadal variations in the two curves, there are a couple of things to note about the graph. First, the PDO data has been inverted; that is, it’s been multiplied by a negative number. Second, the PDO data has also been scaled by a factor of 0.2. That was an arbitrarily chosen round number I used to bring the variations of the PDO down into line with the North Pacific Residual data. But let’s look at the scaling in another way: the multidecadal variations in the PDO data are five times higher than the actual variations in the North Pacific Residual data in that graph. One might conclude the PDO data exaggerates the actual multidecadal variations in North Pacific SST anomalies. More on that later.
Figure 4
Figure 4 is taken from the post An Inverse Relationship Between The PDO And North Pacific SST Anomaly Residuals.
CORRECTION: I have modified the wording of the next paragraph. Note the strikes through the 2 “a” and the replacements with “the”.
The SST anomaly data for the North Pacific is part of the Global Surface Temperature data, but the PDO data is not. This inverse relationship between the PDO and the SST anomaly data of the North Pacific directly contradicts the assumption that a positive (warm) PDO is responsible a the rise in global temperatures or that a negative (cold) PDO is somehow responsible for a the drop in global temperatures.
The IceCap post attempts to resurrect the argument that there is no clear evidence that ENSO drives the PDO. IceCap bases their brief discussion on a quote from the 14-year old Mantua et al (1997) paper “A Pacific interdecadal climate oscillation with impacts on salmon production.” The IceCap post reads, “The authors made no claim as to which (PDO or ENSO) was the chicken and which the egg.” And IceCap includes a quote from Mantua et al (1997):
“The ENSO and PDO climate patterns are clearly related, both spatially and temporally, to the extent that the PDO may be viewed as ENSO-like interdecadal climate variability (Tanimoto et al. 1993; ZWB). While it may be tempting to interpret interdecadal climatic shifts as responses to individual (tropical) ENSO events, it seems equally conceivable that the state of the interdecadal PDO constrains the envelope of interannual ENSO variability.”
That paragraph from Mantua et al (1997) appears to contradict a paper they reference. Mantua et al (1997) calculate the PDO using a method that was presented in Zhang et al (1997) ENSO-like Interdecadal Variability: 1900–93. In Zhang et al (1997), the PDO was identified as “NP”, and they use Cold Tongue Index SST anomalies (CT) as the El Niño-Southern Oscillation (ENSO) proxy. Zhang et al (1997) note:
“Figure 7 shows the cross-correlation function between CT and each of the other time series in Fig. 5. The lag is barely perceptible for TP and G and it increases to about a season for G – TP and NP, confirming that on the interannual timescale the remote features in the patterns shown in Fig. 6 are occurring in response to the ENSO cycle rather than as an integral part of it…”
It would be difficult for the PDO to drive ENSO if ENSO leads the PDO by a season and if the PDO spatial pattern is a “response to the ENSO cycle rather than…an integral part of it.”
In the 14 years since Mantua et al (1997) was published, there have been a number of papers that confirm that ENSO drives the PDO. In ENSO-Forced Variability of the Pacific Decadal Oscillation, Newman et al (2004) also found that the PDO lags ENSO. They describe cell d of their Figure 1 as:
“ENSO also leads the PDO index by a few months throughout the year (Fig. 1d), most notably in winter and summer. Simultaneous correlation is lowest in November– March, consistent with Mantua et al. (1997). The lag of maximum correlation ranges from two months in summer (r ~ 0.7) to as much as five months by late winter (r ~ 0.6). During winter and spring, ENSO leads the PDO for well over a year, consistent with reemergence of prior ENSO-forced PDO anomalies. Summer PDO appears to lead ENSO the following winter, but this could be an artifact of the strong persistence of ENSO from summer to winter (r = 0.8), combined with ENSO forcing of the PDO in both summer and winter. Note also that for intervals less than 1yr the lag autocorrelation of the PDO is low when the lag autocorrelation of ENSO (not shown) is also low, through the so-called spring persistence barrier (Torrence and Webster 1998).”
And the first sentence of the Conclusions of Newman et al (2004) reads (their italics):
“The PDO is dependent upon ENSO on all timescales.”
My post An Introduction To ENSO, AMO, and PDO — Part 3 included the same discussions of those two papers under the heading of DOES THE PDO DRIVE ENSO?
A more recent paper, Shakun and Shaman (2009) “Tropical origins of North and South Pacific decadal variability” also confirms that the PDO is an aftereffect of ENSO. In addition to the PDO, they use the acronym PDV for Pacific Decadal Variability.
The Shakun and Shaman (2009) Conclusions read:
“Deriving a Southern Hemisphere equivalent of the PDO index shows that the spatial signature of the PDO can be well explained by the leading mode of SST variability for the South Pacific. Thus, PDV appears to be a basin-wide phenomenon most likely driven from the tropics. Moreover, while it was already known PDV north of the equator could be adequately modeled as a reddened response to ENSO, our results indicate this is true to an even greater extent in the South Pacific.”
These papers confirm my statements from past posts that the PDO is an aftereffect of ENSO. And that brings us to the two tables from the IceCap post, which I have merged into one graphic, Figure 5. IceCap introduces the tables by stating:
“During the positive phase see the dominance of more frequent, stronger, longer La Ninas and the positive PDO mode, more frequent, stronger and longer El Ninos.”
There is an obvious error in that sentence. It should begin with “During the negativephase…”
Figure 5
Now I do realize that IceCap has not stated that the positive PDO is responsible for the more frequent, stronger and longer El Niño events and vice versa, but they implied it. And that contradicts the papers above. Since the PDO is an aftereffect of ENSO, a period when El Niño events dominated would cause the PDO to be positive, and vice versa for epochs when La Niña events dominate.
A SIMPLE DESCRIPTION OF HOW THE PDO SPATIAL PATTERN IS FORMED
To reinforce the discussion above, the following is a simple explanation of the processes that cause the PDO spatial pattern during ENSO events.
A positive PDO spatial pattern is characterized by SST anomalies in the eastern North Pacific that are higher than the SST anomalies in the central and western North Pacific. That positive PDO pattern is created by the response of the North Pacific SST anomalies to an El Niño event. Changes in coupled ocean-atmosphere processes, resulting from the El Niño, can cause an increase in the SST anomalies in the eastern North Pacific. Since the El Niño causes a reversal of trade winds in the western tropical Pacific, less warm water than normal is spun up into the western and central North Pacific (an area called the Kuroshio-Oyashio Extension or KOE), and SST anomalies of the western and central North Pacific drop. The initial drop in the western and central North Pacific is also driven by the changes in coupled ocean-atmosphere processes that are caused by the El Niño. The reverse holds true during a La Niña in the eastern North Pacific. For the western and central North Pacific during a La Niña, the leftover warm water from the El Niño also gets spun up into the KOE, adding to the warm waters being brought there by the increased strength of the trade winds, both of which raise SST anomalies there.
There are differences between the PDO and an ENSO proxy such as NINO3.4 SST anomalies from time to time. (NINO3.4 SST anomalies are a commonly used proxy for the frequency and magnitude of El Niño and La Niña events.) The reason for this is that other factors can impact how the North Pacific SST anomalies respond to ENSO events. These other factors include shifts in sea level pressure in the North Pacific and a phenomenon called The Reemergence Mechanismalong the Kuroshio-Oyashio extension (KOE). Aerosols from explosive volcanic eruptions should also account for some of the differences between the PDO and an ENSO proxy, though I have never seen this discussed in any papers.
CAN THE MULTIPLE MEANINGS OF THE WORD PATTERN ADD TO THE CONFUSION ABOUT THE PDO?
The Joint Institute for the Study of the Atmosphere and Ocean Joint Institute for the Study of the Atmosphere and OceanJoint Institute for the Study of the Atmosphere and Ocean (JISAO) Pacific Decadal Oscillation (PDO) webpage is a primary source for PDO information and data. Two maps are used by JISAO to illustrate the spatial patterns that can exist during the warm and cool phases of the PDO, Figure 6. I’ve highlighted the area of the North Pacific represented by the Pacific Decadal Oscillation. It is the area north of 20N, and only that area. The word “pattern” in the opening paragraph on that webpage refers to the “spatial climate fingerprint” of the North Pacific north of 20N, not the multidecadal variability of its data. As discussed previously in this post, when the PDO data is positive (warm phase), the SST anomalies in the eastern North Pacific are warmer than those in the western and central North Pacific, and when the PDO is negative (cool phase), the SST anomalies in the eastern North Pacific are cooler than the SST anomalies in the western and central north Pacific.
Figure 6
Farther down on the JISAO PDO webpage, the PDO is described as:
The “Pacific Decadal Oscillation” (PDO) is a long-lived El Niño-like pattern of Pacific climate variability. While the two climate oscillations have similar spatial climate fingerprints, they have very different behavior in time.
Again, the word pattern is being used to describe spatial characteristics of the SST anomalies.
As discussed in An Introduction To ENSO, AMO, and PDO — Part 3, the phrase “El Niño-like pattern” does NOT mean that the North Pacific (north of 20N) has a separate El Niño-like event.It refers to the fact that a typical El Niño event creates a spatial pattern in the North Pacific where it is warmer in the east than it is in the central and western portions, and a typical La Niña event will create the opposite pattern, cooler in the east than it is toward the center and west of the North Pacific.
Figure 7 is a time-series graph that compares the PDO and NINO3.4 SST anomalies (a commonly used proxy for the frequency and magnitude of El Niño and La Niña events). Both datasets have been smoothed with a 121-month filter. Keep in mind that the NINO3.4 SST anomalies represent exactly that, the SST anomalies of an area of the tropical Pacific called the NINO3.4 region, which is bordered by the coordinates of 5S-5N, 170W-120W, while the PDO does not represent the SST anomalies of the North Pacific. The PDO is a statistically manufactured dataset. As illustrated, the multidecadal variations in the PDO and the NINO3.4 SST anomalies are different. Both vary from positive to negative in the mid-1940s and rise from negative to positive in the late 1970s, but the NINO3.4 SST anomalies have an extra period of positive values in the 1960s. As discussed earlier in this post, the reason the PDO has a different “behavior in time” is because the PDO is also strongly impacted by other factors, including sea level pressure and volcanic eruptions.
Figure 7
In summary, on the main JISAO Pacific Decadal Oscillation (PDO) webpage, the word pattern always refers to the “spatial” characteristics of the North Pacific SST anomalies, not its behavior in time.
THE WORD PATTERN CAN ALSO BE TIME RELATED
The second illustration on the main JISAO Pacific Decadal Oscillation (PDO) webpage is a time-series graph of the PDO data. It was missing from the website as I prepared this post. But there are copies posted at other websites. Refer to Figure 8.
Figure 8
On their PDO Index Monthly Values webpage, JISAO uses the phrase “the pattern of variability” to describe the PDO’s “behavior in time” or the periodicity of the PDO data. Refer to the description of the dataset at the top of the page. It reads (my boldface):
Updated standardized values for the PDO index, derived as the leading PC of monthly SST anomalies in the North Pacific Ocean, poleward of 20N. The monthly mean global average SST anomalies are removed to separate this pattern of variability from any “global warming” signal that may be present in the data.
The uses of the word pattern are different, and their intents are different. Does the use of the word pattern in both instances add to the confusion about the PDO? I don’t have the answer. I’m asking the question. Clearly, the use of pattern in the JISAO description of “The ‘Pacific Decadal Oscillation’ (PDO) is a long-lived El Niño-like pattern” relates to its spatial characteristics. Likewise, the word pattern in the JISAO description of their maps, “Typical wintertime Sea Surface Temperature (colors), Sea Level Pressure (contours) and surface windstress (arrows) anomaly patternsduring warm and cool phases of PDO,” refers to the same thing, the spatial pattern.
Note: I mentioned above that there are no El Niño or La Niña events in the North Pacific north of 20N. I have shown, however, that there are secondary releases of heat in the North Pacific from the warm waters left over from an El Niño. These secondary releases of heat from the North Pacific occur along the Kuroshio-Oyashio Extension (KOE) and they occur during La Niña events that follow major El Niño events. Refer to The ENSO-Related Variations In Kuroshio-Oyashio Extension (KOE) SST Anomalies And Their Impact On Northern Hemisphere Temperatures.
DOES THE PDO DATA EXAGGERATE ITS RELATIVE SIGNIFICANCE?
Figure 9 compares the Pacific Decadal Oscillation (PDO) data and NINO3.4 SST anomalies. The scales are similar and that might lead one who is unaware of the differences between the two datasets to believe the two “signals” are similar in magnitude. That’s wrong for a number of reasons. First, the NINO3.4 SST anomalies represent the SST anomalies of an area in the equatorial Pacific, but the PDO data does not represent the SST anomalies of the North Pacific. The PDO data is a statistically manufactured dataset that represents an abstract form of the SST data there. Second, the NINO3.4 SST anomalies are presented in Deg C. The PDO data is not. The PDO data has been standardized.
Figure 9
Unfortunately, as far as I know, there is no PDO data available online that has not been standardized. So to illustrate the PDO data before standardization, one would have to duplicate the process JISAO uses to create it. Two of the three SST datasets JISAO uses are obsolete and the differences between those older datasets and the current spatially complete datasets are significant, so the results could be very different. And we really do not need to go through all of that trouble to show that the PDO exaggerates the variability of the North Pacific SST anomalies. We can show that other ways.
The inverse relationship between the PDO and the North Pacific Residual was illustrated in Figure 4. And as you’ll recall, the North Pacific Residual was calculated by subtracting Global SST anomalies from North Pacific SST anomalies, north of 20N. Both datasets in Figure 4 were smoothed with a 121-month running-average filter and the PDO data was scaled and inverted (multiplied by -0.2) to bring its variations into line with the North Pacific Residual data. For the next illustration, Figure 10, let’s leave the PDO data in its raw monthly form, and only invert (multiply by -1) the North Pacific Residual data. That is, we won’t scale either dataset. As shown in Figure 10, the actual variations in the North Pacific Residual are miniscule compared to those of the standardized PDO data.
Figure 10
The standard deviation of the North Pacific Residual data is 0.177, so to standardize that dataset we divide it by that value, or multiply it by its reciprocal of 5.65. Refer to Figure 11. Note how well the inverted and standardized North Pacific Residual data (using a different SST dataset, HADISST) captures the underlying multidecadal variations of the PDO data.
Figure 11
And we can detrend the North Pacific SST anomaly data to also show how the PDO exaggerates actual North Pacific Sea Surface Temperature variability. Again in this example, both datasets are in their “raw” form, and the detrended North Pacific SST anomalies are inverted (multiplied by -1.0). The PDO data as shown in Figure 12 greatly exaggerates the actual variations in the detrended North Pacific SST anomalies.
Figure 12
To standardize the detrended North Pacific SST anomalies, we’ll divide the data by its standard deviation (0.182), or multiply it by its reciprocal of 5.5. Once again, as shown in Figure 13, much of the multidecadal variability of the PDO can be captured by inverting and scaling the adjusted North Pacific SST anomalies.
Figure 13
Whether we present the North Pacific SST anomalies detrended or as a residual, the PDO data exaggerates the actual variations in North Pacific SST anomalies by a factor of at least 5.5. This may also lead to some the misunderstandings of the effects of the PDO on global temperatures.
CLOSING
The PDO is a useful index. Based on the IceCap post, it is used by meteorologists for weather predictions. The early papers about the PDO discussed its impact on salmon production, so it is also useful in those endeavors. But the PDO cannot be used to explain epochs of global warming or cooling because the PDO does not represent a process through which the North Pacific could raise or lower global temperatures.
This post also illustrated how the PDO data is inversely related to North Pacific SST anomalies and how the PDO data greatly exaggerates the actual variations in the Sea Surface Temperatures of the North Pacific.
In a follow-up post, we’ll discuss the error-filled SkepticalScience post It’s Pacific Decadal Oscillation.
SOURCE
The PDO data and the HADISST anomalies presented in this post are available through the KNMI Climate Explorer:
http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere
Bob Tisdale - Climate Observations 
Bob, I don’t think that the idea of PDO contributing to global temperature variations means a direct contribution of the sea surface temperatures to the anomalies as part of the average. The idea, as I understand it, is that the effects of the PDO extend outside the PDO region. For one thing it seems to move warm anomalies over Western North American land areas during it’s warm phase. This gives good reason to think it should be positively correlated with US climate, at least. During this phase one might also expect cool anomalies over some of the East Asian coast. The net global impact could possibly be of opposite sign to what the anomalies in the region itself are. Incidentally, any idea why the earlier warm anomalies of ENSO associated with the first positive phase of the PDO are not clearly reflected in the SOI? SOI seems to correspond to different low frequency variations than other ENSO related phenomena. Perhaps there is something interesting going on…
timetochooseagain says: “Bob, I don’t think that the idea of PDO contributing to global temperature variations means a direct contribution of the sea surface temperatures to the anomalies as part of the average. ”
It couldn’t work any other way.
You said, “The idea, as I understand it, is that the effects of the PDO extend outside the PDO region. For one thing it seems to move warm anomalies over Western North American land areas during it’s warm phase.”
Land surface temperatures in Northwestern North America go hand in hand with the SST variations in the Eastern North Pacific. But on the other side of the Pacific, land surface temperatures in Eastern Asia are responding to the opposing variations in the Western North Pacific SST.
Bob:
Apologies for being completely off-topic, but as I’m sure you know HadSST3 – the long-awaited revision of HadSST2 – has just been published, and I was wondering if you knew of a site where I might be able to download the monthly means. The data are up on the UKMO site, but they’re buried in 30mb text files that I can’t do anything with.
Bob-“It couldn’t work any other way.”
Why is it that only ENSO is allowed to cause net variations in global climate/weather away from it’s region? If you applied your argument to ENSO then the only contribution of ENSO to global variations would be it’s contribution to the average as a region. Clearly this is not the case.
Roger Andrews: As far as I know, the HADSST3 is only available from the UKMO website. And I believe it’s also incomplete, ending in 2006. When they bring it up to date and start using it in their HADCRUT data, I suspect then we’ll see it in more usable forms.
timetochooseagain says: “Why is it that only ENSO is allowed to cause net variations in global climate/weather away from it’s region?”
Not sure where you’re going with this argument. NINO3.4 SST anomalies are exactly that, the SST anomalies of the NINO3.4 region. The PDO is not SST anomalies of the North Pacific.
The PDO is a valuable tool that is a derived value. The pacific temperatures north of 20N are not important, when the north is cooler it allows the equatorial regions to warm. The PDO trend quite clearly follows the world temperature trend, and by adding solar variation all temperature measurement movements can be explained by natural variation.
Positive PDO correlate with higher incidence of El Nino and vice versa. There is insignificant evidence to say what drives what, but I am with Erl Happ when it comes to the ENSO driver. The strength and direction of the Trades is the initiator of the ENSO cycle which is driven by changes in atmospheric pressure. What drives the changes in atmospheric pressure will be the key to understanding the most important oceanic region.
Geoff Sharp: Your comment above appears to be the same one you left at the cross post at WUWT.
I attempted to ignore you there because you established yourself as someone with zero credibility on the Easterbrook thread at WUWT, starting with your comment that the Antarctic has not warmed in 50 years. For a refresher, start at this comment and read our exchange through the rest of the thread:
When I confronted you with data that contradicted your bogus statement, you attempted to claim that the short-term Antarctic surface stations were the cause of the rise and linked the longer-term surface stations as evidence that the Antarctic had not warmed in 50 years. Then when I plotted that data and showed you that the trends were significantly positive, you attempted to misdirect the readers with additional nonsensical claims.
But since you insist on cluttering this thread with more of your baseless claims, let’s take a look at what you’ve written.
Geoff Sharp says: “The PDO is a valuable tool that is a derived value.”
You must not have read my post, or you elected to ignore what I presented.
Geoff Sharp says: “The pacific temperatures north of 20N are not important… “
Once again, reality offers a different picture, Geoff. The North Pacific north of 20N represents about 15% of the surface area of the global oceans. They, therefore, are a significant part of global surface temperatures. The North Pacific SST anomalies have a higher trend than the Global oceans since 1900. The North Pacific SST anomalies also have a stronger multidecadal variation than the Global Oceans, which illustrates that they contributed to the decline in global surface temperatures from the 1940s to the 1970s and to the rises in global temperatures during the early and latter parts of the 20th Century.
One might conclude from that that the SST anomalies of the North Pacific north of 20N play an important role in the rise in global temperatures, and that contradicts your erroneous claim.
Geoff Sharp says: “….when the north is cooler it allows the equatorial regions to warm.”
It does? The data appears to contradict you on this one, too, Geoff. Please use the following graph to document your statement:
Geoff Sharp says: “The PDO trend quite clearly follows the world temperature trend…
The linear trend of the PDO data is flat, slightly negative, Geoff, while the Global SST anomalies have a positive trend.
But that part of your sentence could be interpreted other ways. Are you now claiming that a rise on Global temperatures dictates the sign of the PDO, or is it vice versa? Regardless, when you decide, please document through what mechanism or process global temperatures would drive the sign of the PDO or through what mechanism or process the PDO would drive global temperatures.
Geoff Sharp says: “…and by adding solar variation all temperature measurement movements can be explained by natural variation.”
You made similar statements on the Easterbrook thread, and when I asked you to confirm the claim with data, you advised me that the datasets could not be plotted together and that I would have to imagine the relationship. Sorry. It doesn’t work that way, Geoff.
And as discussed and linked for you on the Easterbrook thread, I’ve prepared posts that have shown that natural variables can account for 85% of the global warming for the latitudes of 60S to 60N since 1982. And what did you do? You attempted to downplay those findings by erroneously claiming that those latitudes represent only 40% of the surface of the globe, when in fact those latitudes make up 88% of the global surface area. Do you recall your nonsensical statement? Here’s a link to your comment:
Geoff Sharp says: “Positive PDO correlate with higher incidence of El Nino and vice versa. There is insignificant evidence to say what drives what…
I’m beginning to believe that you failed to read my post, because I provided quotes from and links to three papers that indicated that ENSO leads the PDO. But if you have read my post, then YOU elect to ignore the evidence. That’s telling in and of itself.
Geoff Sharp says: “…but I am with Erl Happ when it comes to the ENSO driver. The strength and direction of the Trades is the initiator of the ENSO cycle which is driven by changes in atmospheric pressure. What drives the changes in atmospheric pressure will be the key to understanding the most important oceanic region.”
This is the closest your comment has come to reality. The strength and direction of the trade winds and the surface temperature of the topical Pacific are closely coupled. The east-to-west SST gradient does not exist without the trade winds and the trade winds don’t exist without the temperature gradient. And of course, El Nino events are thought to be initiated by a relaxation in the strengths of the trade winds. And all of that is basic ENSO:
Geoff, you’ve once again illustrated for all who read this thread that your claims have little-to-no basis in reality. You, not me, undermine your credibility. You can respond to part or all of this, but I won’t feel obligated to reply to you. In the future, though, rest assured that if you want to attempt to contradict what I’ve written in a post, I will be happy to illustrate the errors in your comments and to link all of the erroneous claims you have made in our past exchanges.
Good-bye, Geoff.
You get so worked up Bob. You have a theory on the PDO that needs to be tested, but there is no need to take it so personal. Instead of playing the ad hominen card try to look through the red mist and acknowledge that science is a method of testing hypothesis where is this case I think you do not have a strong argument.
The PDO is a standard measurement, and despite your intentions it will not go away. Your repeated attempts to discredit this long time record by trying to isolate the northern pacific SST’s is a side show with little relevance to this derived value that is so important to understanding world climate. Until you can come up with an ENSO driver that in your book produces the PDO, you will always be on shaky ground.
Chill out a little….
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bob
I agree with you entirely that PDO does not reflect North Pacific SST . However I plotted your VOLCANO -ADJUTED EAST PACIFIC SST ANOMAOLIES[90S-90N,180-80W ]and ANNUAL PDO and noted [visual only]close correlation. Perhaps this is the reason some climate researchers use the PDO as a predicter of land temperatures especially in North America as the EAST PACIFIC SST will likely have a strong effect on North American weather. Any comment?
matt.v: I took at look at the monthly East Pacific SST anomalies and the PDO and the variations of the two datasets don’t agree that well over the satellite era. I believe the reason the PDO is used by weather forecasters is simply because of the number of studies that show the impacts of the PDO on North American weather.
matt. v: To put the PDO in perspective, I prepared this graph for a discussion on one of the PDO cross-posts at WUWT. Here’s a comparison of the first principal components of detrended NINO3.4 SST anomalies, Eastern Tropical Pacific SST anomalies and North Pacific SST anomalies north of 20N (which is the PDO). None of the datasets have been standardized. I used it to show the impact of standardization on the PDO:
Thanks Bob
Is there a cyclic pattern to your last garph that you can detect similar to
the figure 9 in your article MISUNDERSTANDING ABOUT THE PDO -REVISED . It seems to show some correlation between PDO and 1 ST PC OF DETRENDED NORTH PACIFIC SST ANOMALIES .
bob
Sorry, I meant figure 9 of ON THE AMO+PDO DATA SET
matt. v: Figure 9 from the AMO+PDO post is this graph:
Are you now saying the graph I posted for you earlier…
…looked similar? If so, it’s because they’re the same data except in Figure 9 from the AMO+PDO post all data has been standardized (divided by its standard deviation) and smoothed with 121-month filters.
Regards
Hi Bob,
Are you aware of any theories as to what may cause the multidecadal periods of El Ninos, followed by (or preceded by, depending on one’s point of view) multidecadal periods of La Ninas, since your post makes clear it is not the phase of the PDO driving it ?
Best Regards,
GW
GW: The multidecadal variability is one of the parts of ENSO where there are lots of hypotheses about the cause, but they all sound plausible, some more than others:
–random atmospheric noise,
–changes in the “background state” [where background state is defined as the time-averaged intensity (t) of the Pacific trade winds, the mean depth (H) of the thermocline, and the temperature difference across the thermocline (DT)],
–the impact of Atlantic sea surface temperatures,
–the asymmetry between El Niño and La Niña events,
–an increase in the amplitude of the ENSO skews the low-frequency component toward El Niño.
In other words, no one knows.
Bob,
I figured as much. I would like to bring another couple of points/questions to the discussion. First, is it unreasonable to say the global temperatures, cool and remain cooler during lengthy periods of the negative phase of the PDO and vice versa ? Your other recent analyses have shown the step changes in temperature of ocean in response to the major el ninos. Have you identified any cooling step changes or trends as a result of past major la ninas, or other oceanic processes ?
One would think that an endless supply of strong el ninos would continually increase ocean temps, even after long el nino hiatuses without some mechanism to reduce them.
Have you explored this aspect of the phenomena to any extent ?
Regards,
GW
GW says: “First, is it unreasonable to say the global temperatures, cool and remain cooler during lengthy periods of the negative phase of the PDO and vice versa ?”
Yup, it’s unreasonable, because there’s no mechanism for the PDO to vary global temperatures. Why not say that global temperatures cool during multidecadal periods when La Nina events dominate?
GW says: “Your other recent analyses have shown the step changes in temperature of ocean in response to the major el ninos. Have you identified any cooling step changes or trends as a result of past major la ninas, or other oceanic processes ?”
In the last 30 years, the east Pacific hasn’t warmed. In fact, if you adjust that subset for the impacts of volcanic eruptions, it shows that it’s cooled over 3 decades.
The South Atlantic-Indian-West Pacific only warmed in response to the major East Pacific El Niño events of 1986/87/88 and 1997/98. (It’s still a little early to tell if the 2009/10 El Niño caused a minor shift). And it also cooled between the major El Niño events.
So that’s two subsets of the global oceans, representing about 86% of the surface of the global oceans, that would show no evidence of long-term warming without major El Niño events.
And that leaves the North Atlantic with the Atlantic Multidecadal Oscillation. For the past 35+ years, it has been warming at a rate that’s much higher than the natural warming of the other ocean basins, but it will eventually peak, flatten and then start to cool.
GW says: “One would think that an endless supply of strong el ninos would continually increase ocean temps, even after long el nino hiatuses without some mechanism to reduce them.
Have you explored this aspect of the phenomena to any extent ?”
Your question relies on “an endless supply of strong el ninos”. The sea surface temperature records of the equatorial Pacific (data based, not reconstructions) are too short to determine the longer-term aspects of ENSO.
Bob: Why not say that global temperatures cool during multidecadal periods when La Nina events dominate?
I would say that. We can also say that during lengthy periods dominated by La Ninas, the PDO phase turns toward negative and tends to remain so – yes ?
Bob: The South Atlantic-Indian-West Pacific only warmed in response to the major East Pacific El Niño events of 1986/87/88 and 1997/98. (It’s still a little early to tell if the 2009/10 El Niño caused a minor shift). And it also cooled between the major El Niño events.
This warming is the step changes you identified. I’m wondering if you’ve analyzed data from the last period of dominating La Ninas, roughly 1947-1976, to see if there were also cooling step changes in these basins (or elsewhere) resulting from the big La Ninas of the era. If not step changes, was there a gradual but steady cooling, or any cooling at all ?
Do you care to speculate as to whether or not the El Nino dominated period has ended, and we are returning to a multidecadal period dominated by La Ninas ?
This coming winter had been looking like we were heading into a mild or moderate El Nino, but the past couple months ot has weakened significantly, and La Nada is presently looking like the most likely condition for this winter. Wolter has said that a La Nada this winter is unprecedented in the 20th century record. I’m sure you’re curious as to what will unfold in the next 12-18 months, and the possible effects on surface and LT air temperatures; are you willing to share what insights you have regarding what we might see ?
Thanks Again,
GW
GW says: “We can also say that during lengthy periods dominated by La Ninas, the PDO phase turns toward negative and tends to remain so – yes ?”
The PDO is also strongly impacted by the sea level pressure of the North Pacific, so you can’t really make that claim.
During the earlier cooling period from 1944 to 1976 there were no El Nino events strong enough to cause an upward shift in the sea surface temperatures of the East Indian-West Pacific.
I believe the El Nino-dominated period ended with the last of the secondary El Nino events that occured after the 1997/98 El Nino, which would have been the 2004/ 05 or 2006/07 El Nino, sometime around then.
Your last question: I don’t make predictions.
Regards
Bob: Your last question: I don’t make predictions.
I’ve seen you say that a few times over the years, but no doubt you have opinions. . . I was hoping I might coax some out of you.
Have you ever heard if any of the NOAA, JPL or academia ocean or ocean/atmospheric scientists use your work ?
Regards,
GW
GW: Regarding this year’s ENSO season, there are some subsurface warm anomalies in the central equatorial Pacific that recent strengthened, which may or may not make it to the surface, and they appear to be working against the cooler surface waters from the eastern equatorial Pacific.
I get visitors to my blog from academia and government science agencies around the globe all the time–about 30% to 50% of my visitors. They know I’m here. It’s unlikely with the current state of climate science (AGW consensus) that they would ever acknowledge my findings since my research shows the sea surface records and OHC data contradict the hypothesis of manmade AGW. Hansen’s bulldog came after me and he failed repeatedly.
Bob: Hansen’s bulldog came after me and he failed repeatedly.
I’ve heard that name since its inception. I think it’s overly generous – GF should be called Hansen’s “lapdog”. If anyone deserves to be called his bulldog, it’s Gavin.
Cheers Bob, and thanks for your time.
GW
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