**5.2 Effects of upcoming grand solar minimum (2020–2053)**

Although in the next 33 years the Sun is entering a period of the reduced solar activity, the modern grand solar minimum, which can be called a 'mini ice age', similar to Maunder Minimum. The GSMs are caused by significantly reduced solar magnetic field imposed by the disruptive interference of two magnetic waves generated by the double dynamo in the solar interior [10]. The first modern GSM1 occurs in 2020–2053 [10, 60] and the second modern GSM2 will happen in 2370– 2415 [10, 60].

Because the solar irradiance and terrestrial temperature already increased since the MM owing to the SIM effects discussed in section 5.1, the terrestrial temperature during the first modern GSM1 is expected to drop by about 1.0C to become just (1.5–1.0=) 0.5<sup>∘</sup> C higher than that in 1700.

The temperature decrease during the second modern GSM (2375–2415) can be estimated calculated as follows. The current temperature increase in 2020 is by 1.5<sup>∘</sup> C, which should increase by 2375 by another 1.5<sup>∘</sup> C (=3 x 0.5C [35]) giving the total increase since 1700 by 3.0<sup>∘</sup> C. The temperature decrease caused by a reduction of solar magnetic field and solar activity during the GSM2 would lead to a reduction of temperature by about 1.0<sup>∘</sup> C. This will produce the total temperature during the GSM2 of (3.0–1.0=) 2.0<sup>∘</sup> C higher than in 1700. After each of the modern GSMs, solar activity is expected to return to normal 11 year cycles as shown in **Figure 1** [10].
