Decadal-Scale NAO Forecast
Based on Solar Motion Cycles
Dr Theodor Landscheidt
Schroeter Institute for Research in Cycles of Solar Activity
Klammerfelsweg 5, 93449 Waldmuenchen, Germany
The North Atlantic Oscillation (NAO) refers to swings in the
atmospheric sea level pressure differences between the Arctic and
the subtropical Atlantic. It exerts a strong control on winter
climate in Europe, North America, and Northern Asia.
The NAO index is defined as the normalized pressure difference
between measurements of stations on the Azores and Iceland. A
positive NAO index indicates a stronger than usual subtropical high
pressure center and a deeper than normal Icelandic low. The
increased pressure difference results in more and stronger winter
storms crossing the Atlantic Ocean on a more northerly track. This
results in warm and wet winters in Europe and cold and dry winters
in Greenland and Northern Canada, while the eastern Unites States
experience mild and wet winter conditions. A negative NAO index
points to a weak subtropical high and a weak Icelandic low. The
reduced pressure gradient results in fewer and weaker winter storms
crossing mostly on west-east paths bringing moist air into the
Mediterranean and cold air to Northern Europe. The east coast of the
United States gets more cold air and snow while Greenland enjoys
mild winters (Hurrell, 1995).
Despite these significant impacts of the NAO, it is not yet known
which climate processes govern NAO variability, how the phenomenon
has varied in the historical past, and to what extent it is
predictable. Hurrel (2003) holds that the variations in the NAO are
largely unpredictable as they arise from internal stochastic
interactions between atmospheric storms and the mean atmospheric
flow producing random fluctuations. He seems to take it for granted
that the NAO is a free internal oscillation of the climate system
not subjected to external forcing. I have shown however
(Landscheidt, 2001a) that the NAO is closely related to energetic
solar eruptions. This external forcing is corroborated by evidence
that other dominant modes of global climate variability like the El
Niño/Southern Oscillation (ENSO) (Landscheidt, 2000a) and the
Pacific Decadal Oscillation (PDO) (Landscheidt, 2001b) are so
closely linked to the sun's eruptional activity and special phases
in solar cycles that long-range forecasts can be based on this
relationship. The last three El Niños and the course of the last La
Niña were correctly predicted on this basis years ahead of the
respective events (Landscheidt, 2002). Moreover, it has been shown
that the coolest phase of the current cold PDO regime is to be
expected around 2007 and the next regime shift from cold to warm
around 2016 (Landscheidt, 2001b).
The inter-annual forecast of ENSO events has meanwhile been
completed by a model that predicts El Niño and La Niña activity on a
decadal scale (Landscheidt, 2003c). A similar model is presented
here for the NAO. The forecasts cover the first half of this century.
2. Analysis of yearly NAO index and forecast of NAO trend <![endif]>
The blue curve in Fig. 1 shows yearly means of the NAO index
covering the period 1825 to 2002. Jones et al. (1997) used early
instrumental data to extend this index back to 1825. Data with lots
of missing values go back to 1821, but were excluded here. The
index is available at the Climate Research Unit of the University of
East Anglia (2003). To see the trend, the time series was subjected
to 30-year moving window Gaussian kernel smoothing (Lorzcak).
The cyclic pattern of the curve is closely linked to a well-
investigated solar motion cycle. I have shown that the North
Atlantic Oscillation (NAO), the Pacific Decadal Oscillation (PDO),
El Niño and La Niña, extrema in global temperature anomalies,
drought in Africa and U.S.A., as well as European floods are linked
to cycles in the sun's irregular orbital motion around the center of
mass of the solar system (Landscheidt, 1983-2003). The rate of
change of the sun's orbital angular momentum L - the rotary force
dL/dt driving the sun's orbital motion (torque) - forms a torque
cycle with a mean length of 16 years (Landscheidt, 2001a,b).
Perturbations in the sinusoidal course of this cycle recur at quasi-
periodical intervals and mark zero phases of a perturbation cycle
(PC) with a mean length of 35.8 years. These zero phases are called
instances of greatest perturbation in the torque cycle (GPTC). As to
details, I refer to Figure 2 of my on-line paper "Solar eruptions
linked to North Atlantic Oscillation" (Landscheidt, 2001 a).
The GPTC phases play an important role in the long-range forecast of
diverse climate phenomena. They indicate, for instance, the peaks of
warm PDO regimes and the coolest phases of cold PDO regimes
(Landscheidt, 2001b) and are closely linked to extended dry and wet
spells measured by the U.S. drought index (Landscheidt, 2003 a). As
to the details and physical implications of the Sun's irregular
orbital motion I refer to my papers "New Little Ice Age instead of
global warming?" (Landscheidt, 2003b) and "Extrema in Sunspot Cycle
Linked to Sun's Motion" (Landscheidt, 1999).
Another approach to the 35.8-year cycle has been presented in Fig. 3
of my paper "Trends in Pacific Decadal Oscillation Subjected to
Solar Forcing" (Landscheidt, 2001b). It has been shown that
absolute values of the torque cycle (|dL/dt|) form a shorter cycle
that plays, e. g., a major role in solar forcing of the North
Atlantic Oscillation (Landscheidt, 2001a) and discharges in river
catchment areas (Landscheidt, 2000c,d). When a Gaussian low-pass
filter suppressing wavelengths shorter than 9 years is applied to
|dL/dt|, new oscillations emerge as shown in Fig. 3 of the quoted
paper for 1721 - 2077. Minima in the smoothed |dL/dt|-curve are
identical with initial phases GPTC in the perturbation cycle. So it
is easy to compute the precise dates of these phases for any period.
Within the range of the investigated NAO index, GPTCs fall at
1829.5, 1867.2, 1901.8, 1933.6, 1968.9, and beyond that range at
2007.2, 2044.9., and 2080.7.
In nearly all of my papers I could show that there are phase
reversals in the climate time series related to solar motion cycles
(Landscheidt 1983-2003). These are not ad hoc inventions, but
computable phases of instability that occur when the zero phase of a
longer solar motion cycle coincides with a zero phase of a shorter
solar motion cycle. The arrow in Fig. 1 indicates a zero phase of
the 179-year cycle, described in my paper "Decadal-scale variations
in El Niño intensity" (Landscheidt, 2003c), which coincides with the
GPTC phase 1901.8.
After the phase reversal around 1902, all deep minima in the NAO
curve coincide with GPTCs indicated by red triangles. Before 1902
the relationship is reversed. GPTCs go along with outstanding
maxima in the curve. Only GPTC 1829.5 does not fit. This could be
an effect of the deteriorating quality of the earliest data in the
index reconstruction. The green triangles point to zero phases of
the second harmonic of the perturbation cycle (SHPC) in between
GPTCs. After the phase reversal they consistently coincide with
maxima in the NAO curve and before 1902 with minima.
The extended maximum between 1890 and 1920 can be explained by the
phase reversal. After the GPTC 1901.8, going along with a maximum, a
minimum was to be expected in the regular course of the
oscillation. Instead, another maximum appeared because of the phase
reversal. The situation is comparable to the Medieval Maximum of
solar activity that can also be explained by such a phase reversal
(Landscheidt, 2003b). Another extended NAO maximum of this kind is
not to be expected in the foreseeable future as the next phase
reversal related to a zero phase in the 179-year cycle will not
occur before 2080.
Accordingly, the oscillatary pattern established after the phase
reversal should stay stable. A forecast of the NAO trend can be read
from Fig. 1. Deep minima in the trend curve are to be expected
around 2007 and 2044 and an outstanding maximum around 2026.
3. Analysis and forecast of NAO winter season
The effects of the NAO are most noticeable in the winter months
December to March (Jones et al, 1997). The blue curve in Fig 2 shows
these seasonal values. They were subjected to Gaussian kernel
smoothing (Lorzcak) with a narrower 15-year moving window to get a
more detailed trend perspective. As can be seen from the figure,
the pattern after the phase reversal is nearly the same as in Fig. 1
so that there is no need to formulate a more differentiated trend
forecast. There is, however, some change in the period before the
phase reversal. The SHPCs (green triangles) are related to maxima,
as after 1902, and more frequent minima go along with the fourth
harmonic of the 35.8-year perturbation cycle (FHPC) indicated by
smaller triangles in cyan colour. Theoretically, this is
interesting, but it has no effect on the development in the
4. Link between NAO and solar eruptions
I have shown in several papers that energetic solar eruptions
(coronal mass ejections, flares, and eruptive prominences) have a
strong effect on diverse climate phenomena including El Niño and La
Niña (Landscheidt, 1983-2003). So it suggests itself to investigate
whether energetic solar eruptions are connected with NAO variations,
too. Not all strong solar eruptions have an impact on the near-Earth
environment. The effect at Earth depends on the heliographic
position of the eruption and conditions in interplanetary space.
Indices of geomagnetic activity measure the response to those
eruptions that actually affect the Earth. Mayaud's aa index (Mayaud,
1973; Coffey, 1958-1999) is homogeneous and covers a long period
back to 1868. So I compared the aa index with the NAO data of this
Figure 3 shows the result. The red curve represents yearly means of
the aa index, normalized to the standard deviation and subjected to
30-year moving window Gaussian kernel smoothing (Lorzcak). The blue
curve shows the yearly NAO index treated in the same way. Between
1940 and present the two time series show a clear positive
correlation. The correlation coefficient is as high as r = 0.81 and
explains 66 percent of the variance. Also from 1868 to 1890 the
correlation is positive and strong: r = 0.80. Between 1890 and 1940,
however, the correlation is negative and reaches r = - 0.83.
Bootstrap re-sampling, making use of 500,000 samples drawn at random
from the observed set, shows that there is less than 1 chance in
50,000 to falsely reject the sceptic null hypothesis of no
The change in the sign of correlation is not as strange as it seems
at first sight. It is a first indication that the quality of the
solar effect on climate depends on the level of solar activity. The
red curve in Fig. 3 shows clearly that the sun's eruptional activity
was much weaker before 1940 than afterwards. It will be rather
difficult to explain the different effect of high and low solar
activity in strict physical terms, but there are at least
indications now where to search for explanations.
Revealingly, the correlation between NAO and sunspot numbers R is
much weaker than between NAO and aa. Between 1868 and 1890 and 1940
to present it is smaller than r = 0.5. This corroborates the
hypothesis put forward in nearly all of my papers that the sun's
eruptional activity is the most potent driving force behind climatic
change, much stronger than the relatively weak variations in the
sun's irradiance in the course of the 11-year sunspot cycle. As GCMs
do not take the effect of solar eruptions into account, they do not
5. Background and Outlook
It is to be expected that the presented results will be dismissed as
a statistical artifact as there is no detailed causal explanation of
the relationship between NAO and solar eruptions in strict terms of
physics. Yet how could this be done as long as climatologists have
no physical explanation of the NAO. The positive and negative modes
of this phenomenon establish covariations, but do not explain them
(Leroux, 2003). Only a few years ago Wanner (1999) commented: "How
and why does the NAO see-saw from one mode to another?
many studies this question remains open and the mechanism of the
flip flop quite mysterious." Quite recently Hurrell (2003), a
specialist at NAO research, conceded that "many open issues remain
about which climate processes govern NAO variability
Mobile Polar High (MPH) dynamics as described by Leroux (1993, 2003)
will contribute to a solution of the problem. <![endif]>
IPCC proponents prayer-wheel-wise repeat the mantra that in recent
decades the effect of solar activity on climate has marvellously
disappeared. Figures 1 to 3 and the statistical analysis of the
correlation between the aa index and NAO up to the present show
clearly that with regard to the North Atlantic Oscillation this is
not true. Just in the decades 1970 to present the correlation
between aa and NAO is closest and reaches r = 0.97. Earlier
investigations have shown that in recent decades the other dominant
modes of climate variability, ENSO and PDO, have been subjected to
such strong solar forcing that forecasts can be based on this
relationship (Landscheidt, 2001b, 2002). So the textbook tenet that
NAO, ENSO, and PDO are free internal oscillations of the climate
system not subjected to external forcing is no longer tenable and
the claim that the solar effect has not been observed for decades is
inconsistent with facts.
Fig. 2 shows that there have been strong variations in the NAO index
in recent decades. Hurrell (2003) thinks that they
provide "relatively strong evidence that
increases in greenhouse
gas concentrations are influencing the recent behaviour of the
NAO." Here he seems to suppose that solar forcing is negligible.
The presented results show that this conclusion is not justified.
IPCC proponents continue to contend that there are no professional
physical models that could explain the effect of solar eruptions on
climate. In Chapter 4 of my paper "Long-range forecast of U.S.
drought based on solar activity" I have given an overview of such
models (Landscheidt, 2003a). Meanwhile, Benestad (2002) has written
a book on "Solar Activity and Earth's Climate" which reviews the
rich literature on physical explanations of the widely reported
correlations between magnetic activity in the outer layers of the
sun and changes in weather and climate on planet Earth up to 2001
(Tinsley, 2003). It is a valuable update of the comprehensive
review by Herman and Goldberg (1978) propagated by NASA before the
beginning of the global warming debate. I am not optimistic enough
to assume that IPCC adherents will read this book, but I am
convinced that it will stimulate research by unprejudiced
independent scientists so that, some day, a detailed physical
explanation of the relationship between solar eruptions and
variations in the NAO will be found.
Benestad, R. (2002): Solar activity and Earth's climate. Springer,
Climate Research Unit of the University of East Anglia (2003):
Coffey, H. E.,ed. (1958-1999): Solar-Geophysical Data Center,
Hurrell, J. W. (1995): Decadal trends in the North Atlantic
Oscillation and relationships to regional temperatures and
precipitation. Science 269, 676-679.
Hurrell, J. W. (2003): The North Atlantic Oscillation: Climatic
significance and environmental effect. EOS 84, No. 8, 25 February
Jones, P. D., Jonsson, T., and Wheeler, D. (1997): Extension to the
North Atlantic Oscillation using early istrumental pressure
observations from Gibraltar and south-West Iceland. Int. J.
Climatol. 17, 1433-1450.
Landscheidt, T. (1983): Solar oscillations, sunspot cycles, and
climatic change. In: McCormac, B. M., ed.: Weather and climate
responses to solar variations. Boulder, Associated University Press,
Landscheidt, T. (1984): Cycles of solar flares and weather. In:
Moerner, N.A. und Karlén, W., eds..: Climatic changes on a yearly to
millenial basis. Dordrecht, D. Reidel, 475, 476.
Landscheidt, T. (1986 a): Long-range forecast of energetic x-ray
bursts based on cycles of flares. In: Simon, P. A., Heckman, G., and
Shea, M. A., eds.: Solar-terrestrial predictions. Proceedings of a
workshop at Meudon, 18.-22. Juni 1984. Boulder, National Oceanic and
Atmospheric Administration, 81-89.
Landscheidt, T. (1987): Long-range forecasts of solar cycles and
climate change. In: Rampino, M. R., Sanders, J. E., Newman, W. S.
and Königsson, L. K., eds.: Climate. History, Periodicity, and
predictability. New York, van Nostrand Reinhold, 421-445.
Landscheidt, T. (1988): Solar rotation, impulses of the torque in
the Sun's motion, and climatic variation. Clim. Change 12, 265-295.
Landscheidt, T.(1990): Relationship between rainfall in the northern
hemisphere and impulses of the torque in the Sun's motion. In: K. H.
Schatten and A. Arking, eds.: Climate impact of solar variability.
Greenbelt, NASA, 259-266.
Landscheidt, T. (1995b): Die kosmische Funktion des Goldenen
Schnitts. In: Richter, P. H., ed.: Sterne, Mond und Kometen. Bremen,
Landscheidt, T. (1998 a): Forecast of global temperature, El Niño,
and cloud coverage by astronomical means. In: Bate, R., ed.: Global
Warming. The continuing debate. Cambridge, The European Science and
Environment Forum (ESEF), 172-183.
Landscheidt, T. (1998 b): Solar activity - A dominant factor in
climate dynamics. http://www.john-daly.com/solar/solar.htm.
Landscheidt, T. (2000 a): Solar forcing of El Niño and La Niña. In:
Vázquez , M. and Schmieder, B, ed.: The solar cycle and terrestrial
climate. European Space Agency, Special Publication 463, 135-140.
Landscheidt, T. (2000 b): Solar wind near Earth: Indicator of
variations in global temperature. In: Vázquez, M. and Schmieder, B,
ed.: The solar cycle and terrestrial climate. European Space Agency,
Special Publication 463, 497-500.
Landscheidt, T. (2000 c): River Po discharges and cycles of solar
activity. Hydrol. Sci. J. 45, 491-493.
Landscheidt, T. (2000 d): New confirmation of strong solar forcing
of climate. http://www.john-daly.com/po.htm.
Landscheidt, T. (2001 a): Solar eruptions linked to North Atlantic
Landscheidt, T. (2001 b): Trends in Pacific Decadal Oscillation
subjected to solar forcing. http://www.john-
Landscheidt, T. (2002): El Niño forecast revisited. http://www.john-
Landscheidt,T. (2003 a): Long-range forecast of U.S. drought based
on solar activity.
Landscheidt, T. (2003 b): New Little Ice Age instead of global
warming. Energy and Environment 14, 327-350
Landscheidt, T. (2003c): Decadal scale variations in El Niño
Leroux, M. (1993): The Mobile Polar High. Global and Planet. Change
Leroux, M. (2003): Global warming: Myth or reality. Energy &
Environment, Vol. 14, Nos . 3 and 4, 297-322
Mayaud, P. N. (1973): A hundred year series of geomagnetic data 1868-
1967. IAGA Bulletin No. 33, IUGG Publications Office, Paris.
Tinsley, B. (2003): Book review: Solar activity and Earth's climate.
Wanner, H. (1999): Le balancier de l'Atlantique Nord. La Recherche
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