Summary
1) Grand Solar Minimum (GSM) and mini ice age
Besides the paper in 2014 in ApJ where we described the method of quantifying the eigen vectors of solar magnetic field, we published the other paper Zharkova et al, 2015 in Nature Scientific Reports https://www.nature.com/articles/srep15689. We shown that the modern GSM is similar to that which happened in 17 century – Maunder Minimum, and to other GSMs happened before every 350-400 years (Oort minimum, Wolf minimum etc).
The paper was presented at the National Astronomy Meeting in Landudno in July 2015 and featured in the RAS press release https://nam2015.org/press-releases/64-irregular-heartbeat-of-the-sun-driven-by-double-dynamo many other media articles. You can type mini ice age to find the links to them.
In 2020 Zharkova has also published an editorial article in the Atmosphere journal https://www.tandfonline.com/doi/full/10.1080/23328940.2020.1796243 explaining how this cooling will act on the terrestrial atmosphere via reduction of ozone layer, change of magnetic field and jets in the terrestrial atmosphere. V.Zharkova also published much more papers in 2018-2021, which explore different aspects of the upcoming GSM and those which happened in the past. You can find them on my website https://solargsm.com under publications.
Recently we confirmed that the modern GSM has arrived in the paper published in Monthly Notices of the RAS Zharkova and Shepherd, 2022 https://solargsm.com/wp-content/uploads/2022/04/zharkova_shepherd_mnras22.pdf.
This paper used another cycle 24 to the data analysis (21-24 cycles), confirmed our previous finding and explained from the SILSO website site that the current cycle 25 has the largest number of spotless days over all other cycles. The GSM is started in 2020 and taking a strength with every year. But the coolest period is expected in 2030-2040 when solar cycle 26 will be the weakest ever recorded.
Since during Maunder Minimum the Earth was cooling significantly, we expect the similar things will happen during the modern GSM (2020-2053). We hope it will go with the scenario close to that of Maunder Minimum which was described in the paper by Shindel et al, 2001 https://earthobservatory.nasa.gov/images/7122/chilly-temperatures-during-the-maunder-minimum mentioned in the editorial paper of 2020.
2). Global warming and link to GSM
Actually, cooling caused by GSM happens simultaneously with a global warming caused by the fact that in this millennium (1600-2600) the Sun moves closer to the Earth orbit’s position of the spring equinox.
In July 2019 we published another paper in NatSR Zharkova et al, 2019 reporting about two-millennial oscillations of the baseline of solar magnetic field suggesting that these variations are caused by solar inertial motion, or gravitation of large planets on the Sun, shifting the sun from the ellipse focus towards the Earth orbit. This SIM happens over the period of 2100 years (Hallstatt’s cycle), which was also detected in the variations of solar irradiance. This suggestion of terrestrial warming coming from the Sun has scared the AGW people and they demanded to retract our paper that was done by the SR Editor on the 4 march 2020.
Then in March 2021 V. Zharkova has been published the book chapter ‘Millennial oscillations of solar magnetic field and solar irradiance and their effect on the terrestrial atmosphere https://www.intechopen.com/chapters/75534.
This chapter confirms that, contrary to the retraction note, our paper Zharkova et al, 2019 was correct when reporting two-millennial oscillations of solar magnetic field. In the chapter I proved with the ephemeris of the Sun-Earth distances that the Sun-Earth distances are decreasing in in this millennium (1600-2600) that leads to the increase of solar irradiance. I even confirmed that the variations of Sun-Earth distances approach 0.016 au per two millennia that was similar to the distance we estimated in the paper Z2019.
This increase of solar radiation in the current millennium is caused by the Sun’s shift from the ellipse focus towards the spring equinox position off the Earth orbit. This process is called solar inertial motion induced by the gravitation of large planets. Nobody on Earth can do this heating we get, only sun can provide the required energy!
This SIM effect explains the global warming on Earth and other planets we had since 1700.
Again since all the energy to Earth comes from the Sun, when Sun enters the grand solar minimum (GSM), as it happens now, the reduction of solar radiation caused by GSM will override the global warming caused by SIM. The Sun is still at the same distance to Earth in 2020-2053, since SIM operates on millennium scale.
You can read section 5 in the book chapter for a brief explanation how the Grand Solar Minima interacts with the global warming.
But this SIM cannot offset the mini ice age induced by GSM because the Sun is the only source of energy for the Earth and all other planets. When it stops firing sunspots and active regions during the GSM, as it happens right now and for the next 30 years, all the planets will feel the chill, similar to that during Maunder Minimum.
3) Summary
Now we have some undeniable facts about the modern GSM:
1. The Sun reveals since 2020 more spotless days than ever been seen between the cycles or at the start of a cycle during the past 360 years https://www.sidc.be/silso/spotless (see also Fig.1 in our recent MNRAS paper https://solargsm.com/wp-content/uploads/2022/03/zhar_etal_mnras_2col_rev2_v1.pdf.
2. The solar activity cycle 25 is approaching its maximum, so the solar radiation yet is not reduced very much. But the observations show the change of leading magnetic polarities of sunspots that appears much earlier in cycle 25 (normally it should appear at the descending phase of a cycle, not at its ascending phase as happens now in cycle 25.
3. Hence, the real cooling will be noticeable after 2025-2026 towards 2030-2035. This can lead to cold and snow in May-june or even to the absence of summers during some years. Winters may become colder in these years, we will need more heating but it is survivable. More difficult will be a survival of shorter vegetation period for wheats, many fruits, vegetables and food for animals.
4. However, even in the past two years the terrestrial temperature started dropping in many locations if you look at the Electroverse reports : snows and cold even in Arabia, very cold winter in Antarctica, increase of the ice area coverage in both Arctics and Antarctica.
5. We also found that in the next cycle 26 (2031-2042) one can expect strong decrease of solar activity. At the same time it is expected the increase of volcanic eruptions that can lead to the additional cooling because of the ashes in the atmosphere. Therefore the years 2030-2045 will be the most challenging ones in terms of reduction of terrestrial temperature..
You can browse my website https://solargsm.com for more recent publications, news and explanations about solar activity and our recent finding published in 2020-2022.
General description
Sun is the main source of energy for all planets of the solar system. This energy is delivered to Earth in a form of solar radiation in different wavelengths, called total solar irradiance. Variations of solar irradiance lead to heating of upper planetary atmosphere and complex processes of solar energy transport towards a planetary surface.
The signs of solar activity are seen in cyclic 11-year variations of a number of sunspots on the solar surface using averaged monthly sunspot numbers as a proxy of solar activity for the past 150 years. Solar cycles were described by the action of solar dynamo mechanism in the solar interior generating magnetic ropes at the bottom of solar convective zone. These magnetic ropes travel through the solar interior appearing on the solar surface, or photosphere, as sunspots indicating the footpoints where these magnetic ropes are embedded into the photosphere.
Magnetic field of sunspots forms toroidal field while solar background magnetic field forms poloidal field. Solar dynamo cyclically converts poloidal field into toroidal one reaching its maximum at a solar cycle maximum and then the toroidal field back to the poloidal one towards a solar minimum. It is evident that for the same leading polarity of the magnetic field in sunspots in the same hemisphere the solar cycle length should be extended to 22 years.
New proxy of solar activity
Summary curve of two principal components of the solar background magnetic field is suggested as a new proxy of solar activity (Shepherd et al, 2014, Zharkova et al, 2015)
Grand solar cycle and Grand Solar Minimum (GSM)
By applying Principal Component Analysis (PCA) to the low-resolution full disk magnetograms captured in cycles 21-23 by the Wilcox Solar Observatory, Zharkova et al., (2012, MNRAS) discovered not one but two principal components of this solar background magnetic field (see Fig. 1, top plot) associated with two magnetic waves marked by red and blue lines.
The authors derived mathematical formulae for these two waves fitting principal components from the data of cycles 21-23 with the series of periodic functions and used these formulae to predict these waves for cycles 24-26. These two waves are found generated in different layers of the solar interior gaining close but not equal frequencies (Zharkova et al., 2015). The summary curve of these two magnetic waves (Figure 1, bottom plot) reveals the interference of these waves forming maxima and minima of solar cycles.
The summary curve of two magnetic waves explains many features of 11 year cycles, like double maxima in some cycles, or asymmetry of the solar activity in the opposite hemispheres during different cycles. Zharkova et al, 2015 linked the modulus summary curve to the averaged sunspot numbers for cycles 21-23 as shown in Figure 2 (top plot) and extended this curve to cycles 24-26 shown in Figure 2 (bottom plot). It appears that amplitude of the summary solar magnetic field shown in the summary curve is reducing towards cycles 24-25 becoming nearly zero in cycle 26.
Figure 2. Top plot: The modulus summary curve (black curve) obtained from the summary curve (Figure 1, bottom plot) versus the averaged sunspot numbers (red curve) for the historical data (cycles 21-23). Bottom plot: The modulus summary curve associated with the sunspot numbers derived for cycles 21–23 (and calculated for cycles 24–26 (built from the data obtained by Zharkova et al, 2015).
Zharkova et al., 2015 suggested to use the summary curve as a new proxy of solar activity, which utilizes not only amplitude of a solar cycle but also its leading magnetic polarity of solar magnetic field.
Figure 3. Solar activity (summary) curve restored for 1200-3300 AD (built from the data obtained by Zharkova et al, 2015).
Figure 3 presents the summary curve calculated with the derived mathematical formulae forwards for 1200 years and backwards 800 years. This curve reveals appearance Grand Solar Cycles of 350-400 years caused by the interference of two magnetic waves. These grand cycles are separated by the grand solar minima, or the periods of very low solar activity (Zharkova et al, 2015). The previous grand solar minimum was Maunder minimum (1645-1710), and the other one before named Wolf minimum (1270-1350). As seen in Figure 3 from prediction by Zharkova et al. (2015), in the next 500 years there are two modern grand solar minima approaching in the Sun: the modern one in the 21st century (2020-2053) and the second one in the 24th century (2370–2415).
Total solar irradiance (TSI) reduction during Maunder Minimum
Let us explore what has happened with the solar irradiance during the previous grand solar minimum – Maunder Minimum. During this period, very few sunspots appeared on the surface of the Sun, and the overall brightness of the Sun was slightly decreased.
The reconstruction of the cycle-averaged solar total irradiance back to 1610 (Figure 4, top plot) suggests a decrease of the solar irradiance during Maunder minimum by a value of about 3 W/m2 (Lean et al., 1995), or about 0.22% of the total solar irradiance in 1710, after the Maunder minimum was over.
Temperature decrease during Maunder minimum
From 1645 to 1710, the temperatures across much of the Northern Hemisphere of the Earth plunged when the Sun entered a quiet phase now called the Maunder Minimum. This was likely occurred because the total solar irradiance was reduced by 0.22% shown in Fig. 4 (top plot) (Lean et al, 1995) that led to a decrease of the average terrestrial temperature measured mainly in the Northern hemisphere in Europe by 1.0-1.5 C as shown in Fig. 4 (bottom plot) (Easterbrook, 2016). This seemingly small decrease of the average temperature in the Northern hemisphere led to frozen rivers, cold long winters and cold summers.
Figure 4. Top plot: restored total solar irradiance from 1600 until 2014 by Lean et al., 1995. Modified by Easterbrook (2016) from Lean, J.L., Beer, J., Bradley, R., 1995. Bottom plot: Central England temperatures (CET) recorded continuously since 1658. Blue areas are reoccurring cool periods; red areas are warm periods. All times of solar minima were coincident with cool periods in central England. Adopted from Easterbrook, 2016 with the Elsevier publisher permissions.
The surface temperature of the Earth was reduced all over the Globe (see Fig.1 in Shindell et al., 2001), especially, in the countries of Northern hemisphere. Europe and North America went into a deep freeze: alpine glaciers extended over valley farmland; sea ice crept south from the Arctic; Dunab and Thames rivers froze regularly during these years as well as the famous canals in the Netherlands.
Role of magnetic field in terrestrial cooling in Grand Solar Minima (GSM)
However, not only solar radiation was changed during Maunder minimum. There is another contributor to the reduction of terrestrial temperature during Maunder minimum – this is the solar background magnetic field, whose role has been overlooked so far. After the discovery (Zharkova et al, 2015) of a significant reduction of magnetic field in the upcoming modern grand solar minimum and during Maunder minimum, the solar magnetic field was recognized to control the level of cosmic rays reaching planetary atmospheres of the solar system, including the Earth. A significant reduction of the solar magnetic field during grand solar minima will undoubtedly lead to the increase of intensity of galactic and extra-galactic cosmic rays, which, in turn, lead to a formation of high clouds in the terrestrial atmospheres and assist to atmospheric cooling as shown by Svensmark et al. (2017).
In the previous solar minimum between cycle 23 and 24 the cosmic ray intensity increased by 19%. Currently, solar magnetic field predicted in Fig. 1 by Zharkova et al. (2015) is radically dropping in the sun that, in turn, leads to a sharp decline in the sun’s interplanetary magnetic field down to only 4 nanoTesla (nT) from typical values of 6 to 8 nT. This decrease of interplanetary magnetic field naturally leads to a significant increase of the intensity of cosmic rays passing to the planet’s atmospheres as reported by the recent space missions (Schwadron et al, 2018). Hence, this process of solar magnetic field reduction is progressing as predicted by Zharkova et al, 2015, and its contribution will be absorbed by the planetary atmospheres including Earth. This can decrease the terrestrial temperature during the modern grand solar minimum already started in 2020.
Expected reduction of terrestrial temperature in modern grand solar minima
This summary curve also indicated the upcoming modern grand solar minimum 1 in cycles 25-27 (2020-2053) and modern grand solar minimum 2 (2370-2415). This will bring to the modern times the unique low activity conditions of the Sun, which occurred during Maunder minimum.
It is expected that during the modern grand solar minimum the solar activity will be reduced significantly as this happened during Maunder minimum (Figure 4, bottom plot). Similarly to Maunder Minimum, as discussed above, the reduction of solar magnetic field will cause a decrease of solar irradiance by about 0.22% for a duration of three solar cycles (25-27) for the first modern grand minimum (2020-2053) and four solar cycles from the second modern grand minimum (2370-2415). This, in turn, can lead to a drop of the terrestrial temperature by up to 1.0oC from the current temperature during the next three cycles (25-27) of grand minimum 1.
The largest temperature drops will be approaching during the local minima between cycles 25 -26 and cycles 26-27 when the lowest solar activity level is achieved using the estimations in Figure 2 (bottom plot) and Figure 3. Therefore, the average temperature in the Northern hemisphere can be reduced by up to 1.0oC from the current temperature, which was grown by 1.4oC since Maunder minimum. This will result in the average temperature to become lower than the current one to be only 0.4oC higher than the temperature measured in 1710. Then, after the modern grand solar minimum 1 is finished, the solar activity in cycle 28 will be restored to normal in the rather short but powerful grand solar cycle lasting between 2053 and 2370, as shown in Figure 3, before it approaches the next grand solar minimum 2 in 2370.