# Nicola Scafetta, Ph. D.

## Research Interests (#)

Earth and Planetary Science, Computational Physics, Statistical Physics, Solar Physics, Space Weather, Auroras, Climate Change, Biophysics, Environmental Physiology, Time Series analysis, Fractal Systems, Complex Systems, Non-Linear Dynamics, Econophysics.

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## Astronomical/Solar/Climate model (#)

My studies suggest that the climate system is characterized by a complex set of specific harmonics at the annual, decadal, secular and millennial time scales throughout the Holocene. The constituent harmonics of the climate system are found to be well correlated and, therefore, likely linked to oscillations found in the dynamics of the Sun, of the Moon and of the planets of the solar system. For example, Figure 1 shows the power spectra (black) of global surface temperature records since 1850 (Global, North, South, Land and Ocean) against a set of major harmonics deduced from the speed of the wobbling Sun relative to the barycenter of the solar system (red area), which is a convenient way to detect a possible set of the major planetary harmonics of the solar system.
Figure 1 shows that there exists a good coherence between the solar and climate power spectra at multiple frequencies. Figure 2 shows a direct comparison between the 20-year and 60-year oscillations of the speed of the wobbling sun (in black) and the equivalent 20-year and 60-year oscillations found in the global surface temperature. A similar common coherence is also found between the temperature and the aurora historical records (see JASTP2010 and JASTP2012a for details). Note that the barycenter movement of the Sun needs to be interpreted just as an approximate “proxy” for the forces and the physical mechanisms acting on the Sun and on the solar systems: no claim is made that the barycenter movement by itself is the physical cause of the observed dynamics because the sun is evidently in free-fall in it.
In particular, the 20-year and 60-year Jupiter/Saturn cycles together with a quasi-millennial cycle were even well-known in the ancient/medieval times as generated by the Trigon of the Great Conjunctions. For centuries Jupiter/Saturn conjunction cycles were believed to be related to climate changes, political/economical shifts and infectious and epidemic disease in history. A 60-year cycle was included in traditional Chinese and Indian calendars (the Brihaspati-Jupiter 60-year cycle), was known to numerous ancient civilizations and also well documented in the works of Kepler, who was trying to understand and forecast weather and climate change by looking at the Sun, the moon and the planets.
How planets may influence solar activity and/or the Earth's climate has been a deep mystery throughout history. Today, some people think that a planetary influence of the Earth is only an astrological superstition. However, also the ancient belief that the Moon was causing the ocean tides on the Earth, a theory strongly advocated by Ptolemy and Kepler upon observations and correlations, was naively opposed by even some prominent scientist such as Galileo Galilei on the mere assumption that a physical mechanism linking the Moon to the ocean tides was not known at the time (up to the 17th century): actually, Galilei dismissed the ancient theory because he claimed to have found the “tidal mechanism” - that is, the Earth orbiting the Sun - but nobody believed him, beginning from Kepler, because the lunar-based empirical tidal models, as those developed by the Northumbrian monk Bede in 725, predicted the tides very well. Therefore, the Moon was the main cause of the tides although the physical mechanism was not known yet. As today everybody knows, about 100 years later, Newton solved the physical problem in favor of Ptolemy and Kepler's empirical arguments with his law of gravity. This historical example teaches us that the development of a scientific theory begins with observations and with the discovery of phenomenological correlations between physical observables. On the contrary, the process of understanding the underlying physical linking mechanisms requires its own time, which may be long. The scientific method requires people to generate a hypothesis, make predictions, testing them and, eventually, polish the hypothesis and start the process again. As in the Middle Ages Roger Bacon understood, the scientific method is based on a repeating cycle of observation, hypothesis, experimentation, and the need for independent verification. Evidently, scientific research is time-consuming. Therefore, a present-day lack of understanding of underlying mechanisms referring to a complex phenomenon cannot be used to naively dismiss empirical evidences under the pretense that "correlation is not causation". If sufficiently good correlations are found and a empirical model based on them is shown to posses hindcast and forecast capabilities, it is perfectly legitimate to investigate the theory that hypothesizes a physical link between the two observables, and this requires its own effort and time.
In any case, I have also proposed (JASTP2012d) a physical mechanism derived from the stellar mass-luminosity relation that, if correct, would imply that planetary tidal forcings may induce a sufficiently large energy signal capable to allow the Sun to synchronize to the planetary harmonics of the solar systems. It should be noted that if the mass of all planets were added to the Sun, the luminosity of the Sun would increase by about 0.5 %. In fact, the Sun is currently on the main sequence of the Hertzsprung–Russell stellar diagram, which means that there should exist a delicate balance between the power dissipated by solar gravity and solar luminosity. Because the planetary tides add a little bit of gravitational work, which oscillates in time, to that already released by the solar gravity itself, the solar luminosity should monotonically respond to that gravitational stimulus and oscillate as well. Moreover the flux of light toward the tachocline and the surface may be modulated by the stretched plasma probably through some sound-like gravitational wave generated in the solar core. Essentially, the sun would work as a great nuclear fusion amplifier of the weak planetary gravitational tides because of its nuclear fusion active core and of its balance with the gravitational forces. Of course other mechanisms related mostly to electro-magnetic interactions may be present as well, which would be facilitated along the Parker spriral of the stellar wind, as it has been hypothesized to explain astronomical observations about stellar activity enhancement due to interactions  with  extrasolar  giant planets.
Note that major critiques against a planetary theory of solar variation are based on simplistic classical-physics arguments such as that the elongations and accelerations induced by planetary tides on the Sun appear to be too small to produce any observable effect. However, simple classical physics has evident shortcomings when attempting to explain solar physics: for example, classical physics predicts that the Sun is just about 10-40 million years old as, in the 19th century, was deduced from the power generated by the Kelvin–Helmholtz gravitational contraction. On the contrary, the Sun is 4.7-billion years old, and today it is clear that classical physics can fail to explain how the Sun works by a large factor. Today everybody knows that the solar power output and long lifetime are due to thermonuclear energy production, which is only regulated by the solar gravity, and nuclear fusion cannot be explained in classical-physical terms. Evidently, a planetary theory of solar variation requires a modern-physical approach together with the novel physics of dynamical synchronization of coupled oscillators, which deal with mechanisms capable to greatly amplify small harmonic forcings. This would also explicate why the 19th century pioneers of the planetary theory of solar variation (such as Rudolf Wolf - the father of the sun-spot number series -, R. C. Carrington and other solar/aurora experts), could not figure out a working mechanism.
Then, solar and planetary oscillations would drive equivalent oscillations in the electric and magnetic properties of the Heliosphere, which have been detected also in the aurora records (JASPT2012a). The solar and heliospheric oscillations likely force the Earth's water-vapor and cloud system through multiple mechanisms (solar irradiance, UV, modulation of the incoming flux of galactic cosmic rays, etc.), and cause equivalent oscillations in the terrestrial albedo up to a 1-3% variations (which is a realistic amplitude as deduced from available data, as I also show in my papers). Oscillations in the albedo can drive equivalent oscillations in the climate system (including atmosphere and ocean oscillations) because they determine the amount of total solar irradiance that reaches the surface and warms it. Other mechanisms may be present as well.
In brief, climate has always changed and people have always studied it, and tried to understand and forecast it since antiquity. Both astrophysical and geophysical elements contribute to climate mutations and the astrophysical elements are usually characterized by cyclical behaviors. My studies suggest that most of the decal-to-millennial variability observed in the climate system at multiple time scales throughout the last 12,000 years (the Holocene) including the Medieval Warm Period (900-1300), the Little Ice Age (1300-1800), the Modern Warm Period started in the 19th century and, in particular, the warming since 1970, can be correlated to the above identified solar/lunar/astronomical natural cycles at multiple time scales.
Also an anthropogenic global climate change effect - greenhouse gas emission (GHG) plus urban heat island (UHI) plus land use change (LUC) - is likely present, but its overall contribution to climate change, also during the last decades, appears secondary to that associated to natural cycles. It is possible that the global temperature will remain approximately steady or perhaps it will slightly cool for the next 2-3 decades, up to the 2030s, because the quasi 60-year cycle entered in its cooling phase around 2002 and the 115-year solar cycle will approach its minimum in 2030s yielding to a new grand solar minimum, which will have its own characteristics and will likely differ from the Maunder and Dalton solar grand minima. The harmonically modeled natural cooling should be strong enough to compensate the projected anthropogenic warming, which cannot be more than a third of what calculated by the current climate models adopted by the IPCC because of geometrical constrains due to the presence of natural cycles. This conclusion also derives from the fact that solar variability at multiple time scales can be approximately reconstructed and, apparently, predicted with planetary tidal cycles plus a solar dynamo cycle.
Figures 9, 10, 11 and 12 show my basic solar variation model constructed by using the two tidal cycles of Jupiter and Saturn on the Sun (periods: 9.93 and 11.86 years) plus the solar dynamo cycle (period: 10.87 years) against proxy records of the temperature and of solar activity (C14 and Be10) throughout the Holocene. The adopted three harmonics have been discovered by spectral analysis of the sunspot number record since 1749 as shown above in Figure 3. In addition, the three harmonics produce quasi 61, 115, 130 and 980 year beat cycles. Of course, many other cycles are present: for example, ocean tides are currently predicted with 30-40 harmonic constituents related to the Sun and the Moon and a similar situation would occur with the planetary tides occurring on the Sun. Therefore, my proposed three-frequency model should be understood only as the simplest working model that can reproduce the major patterns recognized in the data. To improve the precision there is the evident need to add numerous other harmonics.
As observed in the figures, the three-frequency astronomical harmonic model already well correlates to the observed solar and climatic variability at multiple time scales. The model is able to approximately hindcast known solar grand minima that occur at about 115-year intervals (some of them are known as Oort, Wolf, Sporer, Maunder and Dalton solar minima) and the great quasi-millennial cycle responsible for the Roman Warm Period, the Dark Age Cold Period, the Medieval Warm Period, the Little Ice Age and the Current Warm Period, which may last for other two centuries, and many other events in the antiquity. All these cycles are observed in both solar and climate records. For example, Figure 12 shows in red two filtered solar proxy models (Be10 and C14) and a temperature model (HSG) (taken from Bond et al., 2001) and in black the 980-year beat harmonic produced by the three-frequency astronomical model. As the figure shows, the model well captures the millennial solar/climate cycle. The complex patterns seen in the solar data are produced by interference among the constituent solar/tidal harmonics. For example, the multi-decadal grand solar minima emerge when the central 10.87-year cycle interferes destructively with the two Jupiter and Saturn tidal cycles. The finding rebuts another major critique of a planetary theory of solar variation claiming that planetary geometry does not correlate to known solar dynamics. The good correlation exists, but it emerges only if the tidal cycles are coupled with the solar dynamo cycle that likely emerges as a synchronization/resonance response of the hydrodynamics of the convective-zone solar plasma to the internal luminosity oscillations induced by the planetary harmonics. These results would also qualitatively agree with my preliminary studies showing that solar records and climate data present similar complex scaling exponents. Relevant papers: PRL2003, PRE2004, JASTP2012a, JASTP2012c, JASTP2012d.
Figure 13 shows the ACRIM total solar irradiance (TSI) satellite composite against the PMOD composite. The two records imply alternative solar dynamical histories since 1980. Figure 14 shows empirical reconstructions of the solar signature on the climate since 1600 using ACRIM and PMOD since 1980. The black and blue curves highlight how important understanding correctly solar dynamics may be for correctly interpreting climate changes. Note that ACRIM uses the TSI satellite measurements as published by the original science teams, while PMOD adopts “corrected” versions that, however, are rejected by the original satellite experiment teams. ACRIM dynamical pattern (an increase from 1980 to 2000, and a decease since 2000) would be compatible with the 61-year cycle predicted by the astronomical model (see Figure 4) and would explain a significant part of the global warming since 1980. Relevant papers: GRL2005, JGR2007, PhysicsToday2008, JGR2008, GRL2009, JASTP2009, Book2011. The issue is quite important because there may be the possibility that for their climatic simulations the current GCMs are not using sufficient physical mechanisms and are not even using appropriate solar radiative forcing records.

### Astronomical Climate model forecast vs. IPCC (#)

Magnification of Figure 6 that shows the global surface temperature (HadCRUT3): the red curve shows the original global surface temperature record published in the paper JASTP2012b and the blue curve shows the global surface temperature updated to the most current available month. The back curve within the cyan area is the full astronomical harmonic model forecast since 2000 that clearly outperforms the IPCC general circulation model projections (green area). The yellow curve is the harmonic component alone without the anthropogenic component.
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