Oscillations of the baseline of solar
magnetic field and solar irradiance
on a millennial timescaleV. V. Zharkova1, S. J. Shepherd2, S. I. Zharkov3 & E. Popova4,5Furthermore, the substantial temperature decreases are expected during the two grand minima47 to
occur in 2020–2055 and 2370–24156, whose magnitudes cannot be yet predicted and need further investigation.
These oscillations of the estimated terrestrial temperature do not include any human-induced factors, which were
outside the scope of the current paper
Conclusions
Until recently, solar activity was accepted to be one of the important factors defining the temperature on Earth
and other planets. In this paper we reproduced the summary curve of the solar magnetic field associated with
solar activity5,6 for the one hundred thousand years backward by using the formulas describing the sum of the
two principal components found from the full disk solar magnetograms. In the past 3000 years the summary
curve shows the solar activity for every 11 years and occurrence of 9 grand solar cycles of 350–400 years, which
are caused by the beating effects of two magnetic waves generated by solar dynamo at the inner and outer layers
inside the solar interior with close but not equal frequencies6.
The resulting summary curve reveals a remarkable resemblance to the sunspot and terrestrial activity reported
in the past millennia including the significant grand solar minima: Maunder Minimum (1645–1715), Wolf minimum
(1200), Oort minimum (1010–1050), Homer minimum (800–900 BC) combined with the grand solar
maxima: the medieval warm period (900–1200), the Roman warm period (400–10BC) etc. It also predicts the
upcoming grand solar minimum, similar to Maunder Minimum, which starts in 2020 and will last until 2055.
A reconstruction of solar total irradiance suggests that there is an increase in the cycle-averaged total solar
irradiance (TSI) since the Maunder minimum by a value of about 1–1.5 Wm−2 27. This increase is closely correlated
with the similar increase of the average terrestrial temperature26,43. Moreover, from the summary curve for
the past 100 thousand years we found the similar oscillations of the baseline of magnetic field with a period of
1950 ± 95 years (a super-grand solar cycle) by filtering out the large-scale oscillations in 11 year cycles. The last
minimum of a super-grand cycle occurred at the beginning of Maunder minimum. Currently, the baseline magnetic
field (and solar irradiance) are increasing to reach its maximum at 2600, after which the baseline magnetic
field become decreasing for another 1000 years.
The oscillations of the baseline of solar magnetic field are likely to be caused by the solar inertial motion
about the barycentre of the solar system caused by large planets. This, in turn, is closely linked to an increase of
solar irradiance caused by the positions of the Sun either closer to aphelion and autumn equinox or perihelion
and spring equinox. Therefore, the oscillations of the baseline define the global trend of solar magnetic field and
solar irradiance over a period of about 2100 years. In the current millennium since Maunder minimum we have
the increase of the baseline magnetic field and solar irradiance for another 580 years. This increase leads to the
terrestrial temperature increase as noted by Akasofu26 during the past two hundred years. Based on the growth
rate of 0.5 C per 100 years26 for the terrestrial temperature since Maunder minimum, one can anticipate that the
increase of the solar baseline magnetic field expected to occure up to 2600 because of SIM will lead, in turn, to the
increase of the terrestrial baseline temperature since MM by 1.3 °C (in 2100) and, at least, by 2.5–3.0 °C (in 2600).
Naturally, on top of this increase of the baseline terrestrial temperature, there are imposed much larger temperature
oscillations caused by standard solar activity cycles of 11 and 350–400 years and terrestrial causes. The
terrestrial temperature is expected to grow during maxima of 11 year solar cycles and to decrease during their
minima. Furthermore, the substantial temperature decreases are expected during the two grand minima47 to
occur in 2020–2055 and 2370–24156, whose magnitudes cannot be yet predicted and need further investigation.
These oscillations of the estimated terrestrial temperature do not include any human-induced factors, which were
outside the scope of the current paper
https://www.nature.com/articles/s41598-019-45584-3.pdf