The two Principal Components (eigen vectors) derived with Principal Component Analysis from the solar background magnetic field defining two largest magnetic waves of the poloidal field of the Sun are shown to be generated in two layers by the solar dynamo with the dipole magnetic sources. The two magnetic waves revealed a noticeable phase shift between them resulting in the variations of 11-year cycle amplitudes in the summary curve modulated by the envelope curve with a period of 330-380 years defined by the usual wave interference with a small phase shift. This envelope curve defines the grand solar cycles separated by grand solar minima (GSMs), similar to those observed in the past: Maunder, Wolf, Oort and other grand minima. There are the two modern GSMs approaching: GSM1 (2020-2053) and GSM2 (2375-2410). During a GSM a reduction of solar irradiance is expected by about 3 W/m2 from the modern level that causes a decrease of the average terrestrial temperature by about 1.0C. This temperature reduction is already observed for the GSM1 clearly in the Northern hemisphere from the West to East signalling the arrival of Little Ice Age for GSM1.
