Studies by Valentina Zharkova show that the recent dearth of sunspot activity must inevitably lead to the kind of cooling that took place during the Little Ice Age. (Please remember that millions – mullions! – of people died of starvation during the Little Ice Age, when the population was far less than today.)
In this particular paper, Zharkova shows that the Sun has entered the modern Grand Solar Minimum (GSM), which will last from 2020 to 2053. This will lead to a significant reduction in solar magnetic field activity and to noticeable cooling, cooling such as occurred during the Maunder minimum.
Here I will paraphrase that paper.
The Sun has just completed solar cycle 24 – the weakest solar cycle in the past 100+ years – and 2020 saw the beginning of solar cycle 25. During periods of low solar activity such as this modern GSM the Sun will often be devoid of sunspots. This is just what happened at the start of this minimum, because in 2020 the Sun saw a total of 115 spotless days (or 78%). This placed 2020 firmly on track to surpass the space-age record of 281 spotless days (or 77%) in 2019. However, since cycle 25 is still slow in firing active regions and flares, every extra day/week/month that passes extends the null in solar activity. This extension marks the start of a grand solar minimum.
What are the consequences for Earth of this decrease in solar activity?
Let us explore what happened with solar irradiance during the previous grand solar minimum – the Maunder Minimum. During this period, very few sunspots appeared on the surface of the Sun, and its overall brightness decreased slightly.
Temperature plunged during the Maunder Minimum
From 1645 to 1710, during the Maunder Minimum, temperatures plunged across much of the Earth’s Northern Hemisphere. This likely occurred because total solar irradiance was reduced by 0.22%, which lead to a decrease in average terrestrial temperature by 1.0–1.5°C (measured mainly in the Northern hemisphere in Europe). This seemingly small decrease in average temperature led to frozen rivers, long cold winters, and cold summers.
Surface temperatures were reduced all over the Globe, especially in the Northern hemisphere. Europe and North America went into a deep freeze: alpine glaciers extended over valley farmland, sea ice crept south from the Arctic, and the Dunab and Thames rivers froze regularly – as well as the famous canals in the Netherlands.
The temperature decline was related to dropped ozone levels created by solar ultra-violate light in the stratosphere. Since the Sun emitted less radiation during the Maunder Minimum, including strong ultraviolet emission, less ozone was formed, thereby affecting the jet stream.
Role of magnetic field in terrestrial cooling in Grand Solar Minima
In addition to the change in solar radiation during the Maunder Minimum, another contributor to the cooling came from the solar background magnetic field, whose role has been overlooked so far. After the discovery of a significant reduction of magnetic field in the upcoming modern Grand Solar Minimum (and also during the Maunder Minimum), it was recognized that the solar magnetic field controlled the level of cosmic rays reaching planetary atmospheres, including the Earth’s. That significant reduction of the solar magnetic field will undoubtedly lead to an increase in the intensity of galactic and extra-galactic cosmic rays, which, in turn, will lead to a formation of high clouds that will also assist atmospheric cooling (as shown by Svensmark et al. ).
In the previous solar minimum, between cycles 23 and 24, cosmic ray intensity increased by 19%. Currently, solar magnetic field as predicted by Zharkova et al.  is dropping radically, which leads to a sharp decline in the sun’s interplanetary magnetic field. This decrease naturally leads to a significant increase in the intensity of cosmic rays . This process of solar magnetic field reduction, which is progressing as predicted by Zharkova et al. , can cause cooling during the modern Grand Solar Minimum (which, again, already started in 2020).
Expected cooling during Grand Solar Minima
When you look at the graph below, you can see that grand solar minima (and hence, little ice ages) recur in an undeniable cycle.
Solar activity 1200–3300 AD – Zharkova et al
(If you look at the larger version, you can see that we’re just to the left of center of the graph, at the beginning of Modern Minimum #1)
This modern Grand Solar Minimum during solar cycles 25–27 (from 2020 to 2053), and also the forecast Grand Solar Minimum from 2370 to 2415, will bring the same unique and significant reduction in solar activity as occurred during the Maunder Minimum. Similarly, the reduction of solar magnetic field will cause a decrease in solar irradiance by about 0.22% during the same three solar cycles, and yet again during the four solar cycles of the second Grand Solar Minimum from 2370 to 2415.
Zharkova’s full article:
Valentina V. Zharkova
Northumbria University · Department of Mathematics, Physics and Electrical Engineering · BSc, MSc , PhD, FRAS