A new paper in Geophysical Research Letters was brought to my attention by Dr. Leif Svalgaard.
Tropical origins of North and South Pacific decadal variability by Jeremy D. Shakun and Jeffrey Shaman makes some very interesting findings suggesting that both the northern and southern Pacific Ocean has evidence of the Pacific Decadal Variation PDV being driven by ENSO variations. They produced a model, which when run correlates reasonably well with observations.
Abstract:
The origin of the Pacific Decadal Oscillation (PDO), the leading mode of sea surface temperature variability for the North Pacific, is a matter of considerable debate. One paradigm views the PDO as an independent mode centered in the North Pacific, while another regards it as a largely reddened response to El Nin˜o-Southern Oscillation (ENSO) forcing from the tropics. We calculate the Southern Hemisphere equivalent of the PDO index based on the leading mode of sea surface temperature variability for the South Pacific and find that it adequately explains the spatial structure of the PDO in the North Pacific. A first-order autoregressive model forced by ENSO is used to reproduce the observed PDO indices in the North and South Pacific. These results highlight the strong similarity in Pacific decadal variability on either side of the equator and suggest it may best be viewed as a reddened response to ENSO.
They write about the graph above:
…we model PDV as a first-order autoregressive process driven by ENSO as done by Newman et al. [2003]. This AR-1 model is applied to the North and South Pacific separately.
The modeled PDO index at year n is a function of the modeled PDO index at n – 1 and the observed ENSO index (Nino 3.4) at n. These annually-averaged indices are centered on boreal winter (Jul–Jun) for the North Pacific and austral winter (Jan–Dec) for the South Pacific. Per Newman et al. [2003], the coefficients β and α are parameters derived, respectively, by regression of the PDO index on the ENSO index, then autoregression of the residual time series with a lag of one year. h is an uncorrelated noise term not used in our analysis but shown for completeness. a and b are 0.51 and 0.56 for North Pacific PC1 and 0.62 and 0.71 for South Pacific PC1. While Newman et al. [2003] found this simple model did a remarkable job reproducing the observed 20th century PDO index in the North Pacific (r = 0.63 in our study), it yields an even stronger fit to our Southern Hemisphere PDO index (r = 0.71) (Figure 4).
The greater success of the model in the South Pacific may be a function of its larger α and β terms, which indicate that the persistence of SST anomalies and ENSO forcing are more important. The stronger ENSO signal in the South Pacific may derive from the equatorial asymmetry of ENSO SST anomalies in the eastern tropical Pacific, which extend considerably farther to the south than to the north. One implication of this finding is that the South Pacific may be a better place to develop paleo-ENSO records as it appears to contain a ‘cleaner’ ENSO signal.
Conclusion
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.
Leif has a copy of the paper on his website that you can read here
Citation:
Shakun, J. D., and J. Shaman (2009), Tropical origins of North and South Pacific decadal variability, Geophys. Res. Lett., 36, L19711, doi:10.1029/2009GL040313.
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Small typo in your summary section “evidence”
REPLY: fixed, thanks – A
I find the divergence between observation and model in the final few years interesting.
Sun inputs energy, it creates clouds and winds, they drive ocean cycles and oceans drive the climate. Have I understood it right?
Most of the heat on the earth’s surface comes from the sun, and its intensity has been almost constant in these 100 plus years (except for a 0.1%-level fluctuation during a solar cycle).
In view of this, I now suspect, as a chemist not familiar enough with this field, that PDO, PDV, AMO etc. are caused by periodic changes of heat partitioning between the surface and underneath of the ocean, and this in turn is caused by the periodic pattern change of ocean currents (and ultimately by the periodic pattern change in the wind?).
Correct me please if such a speculation is wrong.
Yes, it does diverge the last 8-9 years in both hemispheres, but the N. Pacific diverged around 1933-4 oppositely and not in concert with the South.
1910 also diverges, though briefly and more shallow.
Looks like the data is current to 2007.
How are we doing today?
Tokyoboy, even the sun irradiation was almost constant, fluctuation in cloud cover (earth albedo) would regulate the amount of energy being absorbed in the oceans.
Concerning your thought about oceanic cycles, me as a chemist have similar view as well 🙂
The north and south Pacific’s temperature variations are strongly affected by the warmer equatorial waters spreading out from where the sun shines down most directly all year round.
Whodathunkit?
This “reemergence” theory is a lazy construct, but Figure 1 offers loud hints…
An item appeared about this today in The Telegraph
http://www.telegraph.co.uk/earth/earthcomment/geoffrey-lean/6349529/Sceptics-figures-on-global-warming-simply-dont-add-up.html
Where Geoffrey Lean asserts that:
“Almost all climatologists expect warming to continue in the long term, but – because of natural fluctuations – they disagree about the immediate future. Part of the conclusion of one paper – “global surface temperatures may not increase over the next decade…” – is often cited by the sceptics. They rarely quote the rest of sentence “…as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming”.
You may wish to comment on that statement in the box provided on his page.
It is nice to see that even though complex physical models tend to be the flavour of the day in some circles, reduction to more simple models often holds the key. Or at least are consistent with observations. I always believe that most systems can be reduced to simple models, and if they cant then the model is wrong.
Hmm. Now all they have to do is get their models to simulate the following effect. During significant traditional El Nino events, warm waters travel from the Pacific Warm Pool to the eastern tropical Pacific. The Coriolis effect draws some of that eastbound warm water into the extratropics of the North and South Pacific where it circulates and returns to the tropics a few years later to form El Nino Modoki.
Thanks for the heads-up, Leif.
The main influences on the ENSO seems to be the amount of solar radiation reaching sea surface in the southeast pacific. This is controlled largely by amount of cloud cover, aerosols, and particulates. The volcanoes in the area have thus a very significant input into global climate beyond volcanoes in other regions of the world.
Another major input is the turbidity of the water in the area, which is affected by both storms and runoff, as well as upwellings, plankton blooms, etc. Turbidity impacts the amount of solar energy absorbed and to what depth…
I like their use of a low pass filter to highlight the low frequency component of the SST anomalies in Figure 1.
I have a hunch that a lot of the so called “secular” climate trends would vanish in a puff of Fourier Transform, if the time series were broken down into meaningful frequency components.
Thanks to Dr. Svalgaard for spotting this paper.
OT – Holy global-warming batman, the BBC (news.bbc.co.uk/2/hi/south_asia/8311838.stm) has just shown footage of the Maldives’ cabinet meeting underwater, to sign a request to “the rest of the world” to reduce CO2 concentrations to “safe” levels.
Odd, how no mention is made of [a] the fact that global sea-levels ain’t doing much, [b] enviro-mentalists had previously ripped up an old tree to try to hide the fact that sea-levels local to the Maldives had been falling and [c] coral atolls should, in fact, be immune to gradual sea-level rise as they in fact grow upwards as sea-level rises.
I really, really, think I may be living in an alternate reality…
Cheers
Mark
From the report:
“These annually-averaged indices are centered on boreal winter (Jul–Jun) for the North Pacific and austral winter (Jan–Dec) for the South Pacific.”
Is that correct for ‘winter’? It seems counter intuitive.
“Most of the heat on the earth’s surface comes from the sun, and its intensity has been almost constant in these 100 plus years (except for a 0.1%-level fluctuation during a solar cycle).”
There is the Wilson and Mordvinov study which indicated a possible long term trend towards increasing TSI amounting to about a 0.05% increase per decade. Geophysical Research Letters Vol 30 No 5 2003
Interesting stuff. Surprising that the model drifts away from reality over the last few years, and is trending much cooler. Perhaps something else not captured by the model is driving events – reduced insolation perhaps?
Kate (03:25:44) :
An item appeared about this today in The Telegraph
http://www.telegraph.co.uk/earth/earthcomment/geoffrey-lean/6349529/Sceptics-figures-on-global-warming-simply-dont-add-up.html
Where Geoffrey Lean asserts that:
“Almost all climatologists expect warming to continue in the long term, but – because of natural fluctuations – they disagree about the immediate future. Part of the conclusion of one paper – “global surface temperatures may not increase over the next decade…” – is often cited by the sceptics. They rarely quote the rest of sentence “…as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming”.
You may wish to comment on that statement in the box provided on his page.
………………………………………………………………………………………………………
Kate, what anthropogenic warming?… as far as anyone can tell, the observations are of Natural climate conditions in their entirety…. There are no observations of Anthropogenic warming, merely a hypothesis and some models based on flawed data from bristle-cone pines and Siberian spruce tree rings.
CO2 and Temperature have diverged in the modern satellite record as they did from 1940 to 1979 in the thermometer record. Ice cores going back tens of thousands of years in time, show CO2 lagging Temperature…..
So I ask again…….. What Anthropogenic Global Warming?
(I assume this is the box I was supposed to use for my statement, yes?: )
If anyone already has graphed the “difference” between Observed and Modeled for NP and SP since 1900, please post it. Assuming the observed and model data are both quite accurate, the devil would seem to be in the +/- of the difference.
Tenuc (05:08:55) : said
“Interesting stuff. Surprising that the model drifts away from reality over the last few years, and is trending much cooler. Perhaps something else not captured by the model is driving events – reduced insolation perhaps?”
And possibly increased albedo, cloud cover. Science has a lot of work to to and I recall seeing an earlier IPCC chart showing “low confidence” in many areas of climatology, yet they were very confident in their summary.
Also I an curious about the difference in how 70% of our planet, the oceans, aborb LW radiation vs SW radiation. I understand the energy from SW radiation penetrates far deeper into the ocean surface, and is therefore held within the planets heat budged far longer then LW radiation. Is it possible that some of this energy gets trapped in a thermocline and actually moves into the deep ocean?
The possible combination of short term insolation affects to changes in albedo / cloud cover, and therefore almost instant astmosphere heat content, and long term changes in ocean heat content due to the long term ocean absorbtion from increased solar insolation due to the same changes in albedo cloud cover, appears to open the possbility of dramatic effect both short term and long term from solar changes having very little to do with TSI changes, and everythin to do with clouds.
Am I understanding this correctly, and how well is this being studied?
Thanks in advance for any response.
” So I ask again…….. What Anthropogenic Global Warming?
(I assume this is the box I was supposed to use for my statement, yes?: )”
…There is no detectable warming. The box to state your views are on the page of the originating article that I quoted:
http://www.telegraph.co.uk/earth/earthcomment/geoffrey-lean/6349529/Sceptics-figures-on-global-warming-simply-dont-add-up.html
Hope that clears things up.
tokyoboy, the Sun’s output may have not varied much, but albedo doesn’t need to vary much to greatly change the amount arriving on the oceans.
I find if very interesting that Leif, WUWT’s solar expert in chief, is reading the ocean circultion literature so closely.
So, are events in the air causing the ocean cycles or are events in the oceans causing change in the air circulations ?
Are there any independent ocean cycles imposing their will on the air or are they all products of changes that occur in the air first. A pretty critical issue as regards the plausibility of both the warmist viewpoint and a number of air based sceptical viewpoints such as that of Svensmark and that of our own Erl Happ.
As far as I can see the changes in the air always follow the changes in the sea surface temperatures.