By Andy May

The North Pacific Index (NPI) and the Pacific Decadal Oscillation (PDO)

The North Pacific Index (NPI) is computed from the area-weighted sea level air pressure (SLP) over the region 30°N-65°N and 160°E-140°W. It measures interannual to multidecadal variations in Pacific atmospheric circulation. As explained in Trenberth and Hurrel, the winter Aleutian low pressure system moves on a decadal time scale and changes the climate and sea surface temperature (SST) along western North America and in the Northern Central Pacific. These changes are closely related to the PDO (Pacific Decadal Oscillation), which describes the same multidecadal weather and SST pattern in the same region but is calculated with SSTs using a different statistical method. Other oscillations that describe this pattern or something similar are the Interdecadal Pacific Oscillation (IPO) and the North Pacific Oscillation (NPO).

The NPI and PDO are compared in figures 1 and 2. They are different, but since they describe the same weather pattern, we will discuss them together in this post. The North Pacific SST changes tend to follow sea level air pressure changes by one to two months (Trenberth & Hurrel, 1994). Shifts in either the NPI or PDO cause major changes in the migration patterns of many fish species, as well as many weather and environmental patterns in northern Asia and in North America (Ebbesmeyer, et al., 1990) and (Lluch-Belda, et al., 1989).

As figure 1 shows, the two indices tend to track one another when the NPI SLP scale is inverted. A higher NPI area SLP is called a negative NPI, lower SLP is positive. A positive PDO Index (up on the graph) and lower average SLP over the NPI region indicates warmer SSTs off the west coast of North America and an El Niño pattern in the tropics. A negative PDO and higher NPI SLP indicates cooler temperatures on the west coast of North America and warmer SSTs in the central northern Pacific (see figure 3). Negative PDO values and higher SLP correspond to a La Niña pattern in the tropics. Figure 2 is the same as figure 1, except it only includes the winter months. Winter is when most weather events occur and it is also when the meridional transport of energy to the polar regions is maximal. Since most heat transport is via mid-latitude storms, the NPI and PDO effects in winter are more easily seen.

Figure 2 shows that the two oscillations visually correlate better in the winter months. Of the Pacific oscillations, NPI shows the best correlation to HadCRUT5, with the PDO not far behind, and both are closely related to ENSO (aka the ONI). In fact, all the Pacific Oscillations are closely related to one another. Some of them may be teleconnections, or channels, for distributing the energy flux generated by ENSO.

Figure 3 shows the NPI region and compares the positive and negative PDO to the high and low NPI SLP. The positive PDO and a positive NPI (low NPI region SLP) indicate the same SST pattern. According to Trenberth and Hurrell, the sluggish response of the large mid-latitude NPI region of the North Pacific to changes in ocean forcing effectively serves as a low-pass filter and causes this region to show long-term changes in Pacific climate.

The Pacific is the world’s largest ocean, and one would think these oscillations would have a huge influence on the HadCRUT5 global mean surface temperature (GMST), but it isn’t seen in the PDO itself. The data used to create the PDO has the global climate signal removed by subtracting the global mean SST from each point prior to the analysis (Zhang, et al., 1997) & (Hare, 1996). This is done because the leading PC (principal component) of the raw PDO is very heavily correlated (0.7) with the global mean SST (Zhang, et al., 1997). So, the correlation is there, we just don’t see it in the PDO. This removal is not done to the NPI, which is probably why it is more strongly correlated to HadCRUT5.

As we saw in the last post, the mean total Pacific SST only correlates with HadCRUT5 in the middle 20^th century. In particular, it has a poor correlation in recent decades when we have the best data. Whether this is because HadCRUT5 is flawed, or the Pacific is unrelated to recent global warming is an open question.

The Pacific Oscillations (see the list of the top 10 in table 2 here) impact global climate, especially around the Pacific Ocean, but do not correlate well with HadCRUT5. This is odd, especially considering the Atlantic Oscillations correlate better, see figure 1 here.

Characteristics of the NPI and PDO

While Trenberth and Hurrel named and described the NPI in 1994, the very similar PDO was not named until 1996 when Steven Hare suggested the name. It was later more fully described by Yuan Zhang, Nathan Mantua, Steven Hare, and colleagues in 1997 and 2002. A more detailed history of the frantic “race to describe” the well-known North Pacific weather pattern during the 1990s is given in Mantua and Hare (2002). The best early statistical descriptions of the formal PDO used today are by Zhang, et al. (1997) and Hare (1996).

A weak mirror image of the anomalies illustrated in figure 3 occurs across the South Pacific and will be discussed in a later post on the Interdecadal Pacific Oscillation or the Tripole Index (TPI). Overall, the PDO’s spatial pattern resembles that of ENSO, also discussed in a later post. The largest distinction between the PDO and ENSO are their timescales. While ENSO is primarily an interannual phenomenon, the PDO is decadal to multidecadal in scale. Thus, relatively long data records are needed to define and understand the PDO (Deser, NCAR, 2015, link).

Periodic multidecadal changes in the North Pacific climate were first recognized by studying patterns in salmon, sardine, and anchovy populations and other environmental factors along western North America and the Japanese east coast (Hare, 1996), (Lluch-Belda, et al., 1989), and (Ebbesmeyer, et al., 1990). Steven Hare recognized the connection between the environmental and fishing patterns in the North Pacific and the patterns in Pacific SSTs (sea surface temperatures) in 1996 while working on his PhD thesis and named the oscillation the “Pacific Decadal Oscillation” or PDO. We have established that the NPI is very similar climatically to the PDO, so in the rest of this post we will only refer to the PDO, but we mean both.

Figure 4 shows the ERSST v5 PDO further into the past. The PDO climate and environmental shifts that are well recognized are shown with solid lines and one that is sometimes mentioned in the literature and sometimes overlooked is shown with a dashed line. These climate and environmental shifts are most easily seen in fishing records, for example, after the 1947 shift shown in the PDO in figure 4, the salmon crop in Alaska dropped between 33% and 64%. In the same area, it increased 208% to 252% after the 1977 step change (Mantua N. J., et al., 1997).

Salmon fishing is just one Pacific environmental variable that changes with the PDO. Curtis Ebbesmeyer and his colleagues document 40 environmental variables that changed in a coordinated fashion at the 1977 climate shift (Ebbesmeyer, et al., 1990).

The best data for determining the PDO index is after 1950 and from 1950 to today the largest and most dramatic feature is the 1976-77 shift (Zhang, et al., 1997). Data from 1900 to 1950 is decent and both the 1926 and 1947 features are well established. The data prior to 1900 is not very good and that is probably why the apparent shift in 1898 is not discussed more often.

Figure 5 shows that the PDO can signal a significant change in global climate, but not always. The two exceptions are in the 19^th century and since 1997. The climate shift in 1926 signaled a period of rising temperature, the 1947 shift signaled a period of cooling, and the 1977 shift a period of warming. The shift in 1997 seems to have no global warming effect.

If one assumes that the global mean SST is mostly due to CO₂, then this effect needs to be removed, as is done in the PDO calculation. If we assume that global circulation patterns, like the PDO are contributing to global warming, then removing the global mean SST is a mistake. Since we don’t know whether either assumption is correct, we should consider both results. The global mean is not removed from the NPI, and it still shows a good correlation to the PDO. The NPI does not drop as dramatically as the PDO in recent years, see figures 1 and 2.

Discussion

The Pacific Decadal Oscillation is not directly based on trends in the average SST of a region like the AMO is, and the inputs to the calculation have the global mean SST removed, so it is less likely to reflect GMST. Trenberth and Shea recommend that the global mean SST be removed from the AMO region SSTs rather than detrend them with a least squares line, but I do not since it assumes that global trends are due to CO₂, when that may not be the case.

The PDO/NPI reflect the pattern of SSTs and wind patterns across the Northern Pacific as shown in figure 3. Which pattern exists, positive or negative, has a large impact on fishing and many other environmental factors in the Pacific region, the northwestern U.S., and off the east coast of Japan. Thus, the wind/ocean circulation patterns, along with SST, radically affect the Pacific environment.

According to Franco Biondi and colleagues’ tree-ring chronology created using trees in Southern California and Baja, the PDO extends back at least to 1661. Their chronology clearly shows the climate shifts in 1947 and 1977 and has a prominent bi-decadal oscillation (Biondi, et al., 2001). The most significant oscillations in their reconstruction were in 1750, 1905, and 1947. These are all dates of significant global cooling. If the PDO has had the global mean SST removed and it still strongly identifies global climatic events, does this mean it helped cause them? Seems logical.

It is common to hear the “consensus” say that circulation patterns don’t matter regarding global warming because all they do is move thermal energy around Earth’s surface and it is only the radiation in and out of the climate system that matters. Well, global warming is not climate, and climate is not global warming, especially when we all know that oceans limit Earth’s mean surface temperature to less than ~30°C (Sud, Walker, & Lau, 1999). Further, the climate system provides energy storage capacity that varies, it also uses some of the energy to power storms, which transport energy from one location to another. For more on Earth’s natural thermostat and “global” warming’s impact on humans see here, and the references therein.

The Northern Pacific environment appears to be largely controlled by circulation patterns and only secondarily by global average warming and cooling. Circulation patterns matter, it is possible that the Pacific significantly affects global warming and cooling and not the other way around. Both conclusions are possible and reasonable. Attempts to remove the CO₂ portion of warming by removing global average SST from indices are invalid because we cannot assume that all global warming over multidecadal periods of time is due to CO₂.

A Word about the Pacific Oscillations in general

As discussed in my last Climate Oscillations post, The Pacific Mean SST, the Pacific Climate Oscillations are an enigma. They are a very important influence on climate and the environment in the Pacific itself, the Americas, and all of eastern Asia and Australia, but they do not correlate very well with the leading surface temperature records. This is only partially by design. The leading estimates of surface mean temperature are HadCRUT5 and BEST. Figure 6 compares them.

It is clear that the HadCRUT5 (gray) and BEST (blue) reconstructions are nearly identical, yet they do not compare very well to any of the Pacific Ocean Oscillations or to the warming trend of the Pacific Ocean, which covers 33% of Earth’s surface and clearly influences weather over at least half the globe. In recent decades HadCRUT5 and BEST do compare well to the AMO, but the AMO has been in a warming trend relative to the rest of the world since the 1970s (see figure 1 here). For these reasons, it is not clear if the Pacific is telling the most accurate story about global warming or HadCRUT5/BEST are. The accuracy of both HadCRUT5 and BEST is in doubt. In any case, we will continue to discuss the remaining important climate oscillations, most of these are in the Pacific.

Download the bibliography here.

Guest “Just when you thought Democrats couldn’t get any dumber” by David Middleton

Whitehouse: ‘I Can’t Prove It’, But I Think Fossil Fuel Industry Getting Trump to Undercut Weather Forecasting

By Ian Hanchett 10 Jul 2025

On Thursday’s broadcast of MSNBC’s “The Last Word,” Sen. Sheldon Whitehouse (D-RI) stated that he “can’t prove it” but believes that the fossil fuel industry is trying to get the Trump administration to undercut weather forecasting because “They know that when people talk about the weather and give weather warnings, they’re going to talk about climate change now.”

[…]

Breitbart

How can a person become this stupid? Does this total fracking moron not realize that accurate weather forecasts are critically important to oil & gas operations, particularly offshore operations?

Well, it appears that it is very easy to be this STUPID when you’re Sheldon Whitehouse. Stupid, corrupt, vindictive and, did I mention stupid?

Climate Policy Enemies List

Whitehouse has delivered more than 200 speeches on the Senate floor dedicated to climate change and other environmentalist topics. ⁹ He has accused some in the energy industry of acting like “thugs” who “own the joint” (meaning the U.S. Congress), and has declared government officials who oppose him to be “stooges” of the energy industry. ⁹

In a May 2015 opinion piece in the Washington Post, Whitehouse advocated a federal lawsuit against the energy industry using the Racketeer Influenced and Corrupt Organizations (RICO) Act. ⁴ Originally designed for and used in criminal cases to prosecute the mafia, RICO has a civil-lawsuit component that has since been applied to corporate targets such as cigarette manufacturers. Whitehouse admitted he did not “have enough information” to know whether “racketeering activity” had actually occurred with the energy industry, but speculated the civil discovery in a RICO lawsuit might uncover the evidence. ⁴ In March 2016, then-U.S. Attorney General Loretta Lynch announced she had referred Whitehouse’s RICO concern to the Federal Bureau of Investigation (FBI). ¹⁰

In July 2016, two months after the Attorney General of the U.S. Virgin Islands sent a subpoena demanding private internal research records, communications, and donor information to libertarian think tank Competitive Enterprise Institute (CEI), Whitehouse led a group of 19 U.S. Senate Democrats in a two-day series of floor speeches denouncing CEI and many other free-market think tanks, with Whitehouse saying the research organizations were part of a “filthy thing in our democracy.” The Senate campaign was aimed at passage of a Congressional resolution that would have called on the non-profit groups to cooperate with “active or future investigations” of their climate-policy positions that might be launched against them by federal or state law enforcement officials. ¹¹

The CEI president responded, saying Whitehouse had become the “new Sen. Joe McCarthy,” and that it “is unhealthy for democracy and abusive when members of Congress create an enemies list based on policy positions.” ¹¹ A joint letter sent to all of the Democratic Senators from 22 targeted think tanks stated: “Your threat is clear: There is a heavy and inconvenient cost to disagreeing with you. Calls for debate will be met with political retribution. That’s called tyranny. And, we reject it.” ⁵

Whitehouse demanded a more-serious pursuit of a RICO case in 2018 and complained that Democrats still “haven’t done the basic due diligence prosecutors do putting an org chart together against a criminal enterprise.” ¹²

Influence Watch

[This excellent comment was made by John C. in response to one by Kevin (a.k.a. Manicbeancounter) on Mark’s To B or Not To B? thread. It deserves elevation to a head post so that more readers will see it. Thanks to John C. for agreeing to this — Scepticus]

Kevin (at 04 Jul 25 at 3:12 pm), when discussing the importance of narratives here on the Cliscep site we should probably first refer to our own Andy West’s work in his “The Grip of Culture” [Ref. 1].  In a work of well over 430 pages he mentions ‘narrative’ over 450 times.

Andy writes at page xii, “I was by then quite familiar with the power of cultures; given enough latitude they can overwhelm reality in the public consciousness, and their grip can subtly extend into organisations of all kinds before anyone notices their fundamental irrationality.”  At page xiv he continues, “Unless anyone can think of a better explanation, the measurements (now greatly expanded for this book) do indeed robustly confirm a culture of climate catastrophism across global publics.”

Thus Andy’s work shows the huge (and sometimes overwhelming ) influence that cultures and their associated narratives can have on societies.  It is notable that, in the context of climate, the narrative of catastrophism has overwhelmed large sections of the Western world (especially media and governments) but, fortunately for them, societies less closely linked to the West are largely free of such tunnel vision.

I propose to take what I think is a different but complementary view to Andy’s which will be based upon bureaucracies because so much of human activity is directed by organisations that have some form of internal structure (e.g. hierarchy) and which may reasonably be called bureaucracies.  Specifically, I am concerned with (i) how they may operate internally, and (ii) how they may interact with other actors in the public (especially political) arena.  I will start with the latter:-

The Iron Triangle of Bureaucratic Operation

I have previously mentioned this mechanism elsewhere on Cliscep but it bears repeating in this context where, in the UK, in addition to our continuing CCA/NZ challenges, we have just passed through the majority of the Covid event.

The Iron Triangle is a well-known phenomenon related to policy making.  It is shown in diagram form in [Ref. 2] and is described in written form by Endress in [Ref. 3].  It is worth quoting at length from the latter.  After describing the first- and second-best levels of policy making, Endress continues:-

“Third-best is the world of political economy, wherein costs and benefits directly influence the formation of coalitions that compete for political and economic advantage in society.  The pursuit of such advantage is called “rent-seeking” in economics and typically involves activities such as lobbying, public relations campaigns, political contributions, and, sometimes, outright bribery.  Unfortunately, the expansion of government that accompanies intervention on second-best grounds can facilitate rent-seeking at the third-best level … A particularly powerful type of rent-seeking coalition, long studied in political science, is termed “the iron triangle” because of the strength of the collaborative relationships among a triad of actors: politicians who seek campaign contributions, votes and reelection; government bureaucrats who aspire to expand fiefdoms and budgets; and private sector interest groups who seek special privileges in the form of political access, favourable legislation, subsidies, protection of monopoly positions, and lucrative government contracts.  The iron triangle is durable and impenetrable because it functions as a highly efficient, three-cornered, rent-seeking machine.

Nowhere (except perhaps in healthcare) do third-best politics sink first-best and second-best economic considerations as deeply as in the realm of energy policy.  In assessing energy policy in Europe and the United States, Helm (2012) is especially critical of policymakers’ obsession with current technology renewable energy, which is not yet commercially viable without government subsidies and mandates … Consequently, renewables have remained ineffective in lowering energy prices, creating green jobs, and reducing carbon emissions worldwide.  The result is high costs for little gain.  In a review of Helm’s book, “The Carbon Crunch,” The Economist … highlights Helm’s observation that the entire renewable sector has become an “orgy of rent-seeking.”  This outcome is not compatible with the sustainability criterion.” End of Endress quote.

I find it telling but not surprising (given the importance of these topics to humanity) that Endress is here describing (a) not the best approach to governance but the third best form, and (b) he has noted that energy and health policies are particularly susceptible to influence under the lower standards of governance.

The Iron Law of Oligarchy [Ref. 4]

Given that the Iron Law of Oligarchy was proposed by Robert Michels well over a hundred years ago I am somewhat surprised that it is not known much more widely given its potential for explaining much of the behaviour of some bureaucracies over the years, and in particular those behaviours that favour outcomes which are very different from those originally sought.

Ref. 4 states that the Iron Law of Oligarchy “asserts that rule by an elite, or oligarchy, is inevitable as an “iron law” within any democratic organization as part of the “tactical and technical necessities” of the organization … [A]ll complex organizations, regardless of how democratic they are when started, eventually develop into oligarchies. Michels observed that since no sufficiently large and complex organization can function purely as a direct democracy, power within an organization will always get delegated to individuals within that group, elected or otherwise. As he put it in Political Parties, “It is organization which gives dominion of the elected over the electors. […] Who says organization, says oligarchy.” … Far from being servants of the masses, Michels argues, this leadership class, rather than the organization’s membership, will inevitably grow to dominate the organization’s power structures.”.

Ref. 4 also describes the possible implications of the Iron Law in these terms, “The “iron law of oligarchy” states that all forms of organization, regardless of how democratic they may be at the start, will eventually and inevitably develop oligarchic tendencies, thus making true democracy practically and theoretically impossible, especially in large groups and complex organizations. The relative structural fluidity in a small-scale democracy succumbs to “social viscosity” in a large-scale organization. According to the “iron law”, democracy and large-scale organization are incompatible.”

Taken together, the Iron Triangle and the Iron Law form a potentially very powerful disruption to the correct operation of bureaucracies as conceived by their creators.  In the extreme, those bureaucracies could, in principle, be completely redirected from their original purposes.  To what extent has complete redirection or misdirection taken place in reality?

Effects in the Real World?

It is interesting, but somewhat depressing, to speculate as to what effects the Iron Triangle and the Iron Law may have had – and may still be having – on our lives today.  For example, if catastrophist narratives influenced the oligarchies operating within large swathes of Western governments and their quangos, plus within major media organisations, major businesses and charities then, to consider just two thought experiments, some of the following perverse outcomes might occur:-

Suppose a major bird protection charity starts to believe that current renewables technology must be adopted in order “to save the planet” then perhaps the charity (i) would promote farms of solar panels where wildfowl would mistake them for water surfaces, and (ii) would advocate the erection of wind turbines in areas where these turbines could, throughout the life of the wind farm, mince up large numbers of birds, bats and insects.

Or suppose that governments, their public health agencies and large pharmaceutical companies collectively came to believe that a deadly pandemic was in progress and from which the only escape would be the rapid development of a “safe and effective” vaccine.  In such an instance perhaps the vaccine’s safety might be inadequately tested due to the rapid development timescale required in order to release the population from repeated pandemic lockdowns.  What then would be the medical effects of the premature application of a potentially unsafe vaccine?

Correcting Narratives and Improving Governance

The Iron Triangle model suggests that moving to a ‘first best’ model of governance would improve matters for the populace (i.e. moving away from a semi-failed state model back towards competent government), while the Iron Law suggests that continual vigilance (followed, where necessary, by corrective action) of major national and international organisations (and treaties with them!) would help to avoid countries being suborned internally and compromised internationally.  However, many vested interests will oppose such improvements; group-think, tunnel vision and motivated reasoning are the dependable allies of vested interests.

In an era of 24-hour news (which, in the absence of severe censorship, will likely continue indefinitely) then avoiding panicked, snap decisions at senior levels, although very difficult, may lead to better long-term outcomes.

However, looking back at British history over decades the list of state failures is long; the Establishment has protected (and is protecting) itself at every turn.  Thus the sine qua non of better governance in the British context is probably the election of a government that sees itself primarily as serving the electorate, probably through root and branch reform, rather than serving those unelected and anti-democratic forces which, for far too long, seem to have inhabited the corridors of power.

Causal Underdetermination

Thus far I have not addressed in this note the issue of the fundamental scientific causal underdetermination which you raised, Kevin.  As this note has been concerned primarily with the possible misdirection of the efforts of Western organisations (both within and without nation states) I will not here switch horses to discuss in detail the very different but very relevant issue of underdetermination.

For now it is sufficient to note that the narrative adopted by many Western states, namely that of dangerously rising temperatures driven mainly or exclusively by unabated CO2 emissions, gravely hobbles the economies of those nations which try, at all costs, to mitigate any such climate change, while harming not at all those nations which reject (and perhaps even laugh at) the catastrophist CO2 narrative.   

References

1. https://thegwpf.org/content/uploads/2023/07/West-Catastrophe-Culture6by9-v28.pdf
2. https://en.wikipedia.org/wiki/Iron_triangle_(US_politics)#/media/File:Irontriangle.PNG where the interest group could be, for example, a university, an NGO, or a green organisation, etc.
3. Arsenio Balisacan et al. (editors), “Sustainable Economic Development: resources, environment and institutions”, Academic Press, 2014, especially section 3.4.2 by Lee H. Endress, ‘Public policy: prosustainability or not?’, pages 57 -58.
4. https://en.wikipedia.org/wiki/Iron_law_of_oligarchy