The astronomical theory of climate changes (oscillations), created more than 100 years ago by the Serbian mathematician Milutin Milanković, in its current form does not explain global fluctuations of the natural environment in the Late Pleistocene, and therefore requires further refinement and development. And this theory has been modernized. Our revision is based on the results of calculations of the Earth’s insolation, performed with a high spatiotemporal resolution. The irradiation of the entire Northern Hemisphere was taken as the basis for determining the causes of the glaciations in Late Pleistocene. Variations in incoming solar radiation, calculated within the astronomical theory of climate, were supplemented by calculations of variations in the characteristics of radiative heat transfer. Based on the improved astronomical theory, the causes of global climate changes in the Late Pleistocene were found. The effect of dividing seasonal irradiation by phases of annual irradiation of the hemispheres was determined, and on this basis 7 warm and 9 cold solar epochs are distinguished in the solar climate of the Late Pleistocene. It has been determined that the glacial epochs in the Late Pleistocene of Northern Eurasia are associated with periods of positive average anomaly of winter meridional heat and moisture transfer and negative average anomaly of summer irradiation intensity in the Northern Hemisphere. Also, positive average anomalies of radiative heat transfer from the summer Southern Hemisphere to the winter Northern Hemisphere, as well as negative average anomalies of insolation seasonality in the Northern Hemisphere, correspond to glacial periods in the Late Pleistocene.

Interglacial epochs are associated with periods of positive average anomalies of summer radiation intensity and negative average anomalies of winter meridional transfer, and interhemispheric transfer of heat and moisture from the summer Southern Hemisphere to the winter Northern Hemisphere. Also, interglacial periods in the Late Pleistocene correspond to negative average anomalies of radiative heat transfer from the summer Southern Hemisphere to the winter Northern Hemisphere, as well as positive average anomalies of insolation seasonality in the Northern Hemisphere. The difference in the intensity of summer irradiation of warm and cold climate epochs in 100-thousand-year cycles averages 4.91 W/m2 (or 1.151% of the average Late Pleistocene value of summer irradiation intensity for the Northern Hemisphere). Therefore, the change of paleoclimatic epochs is associated mainly with the dynamics of the characteristics of summer radiation, and with the winter transfer of radiative heat and moisture determined by astronomical factors.

Based on our previously performed calculations of irradiation with high spatial and temporal resolutions, using data from high-precision astronomical ephemerides, changes in the intensity of summer irradiation in the polar and equatorial 5-degree latitude zones of the Northern Hemisphere were analyzed. Over the period of 1900–2050 AD, a decrease in the intensity of summer irradiation in the polar region and its increase in the equatorial region were observed. The consequences of this phenomenon are an increase in the meridional gradient of insolation and an increase in the intensity of the meridional transfer of radiative heat associated with the rise of land surface air temperature and ocean surface temperature in the Arctic.

The faster temperature increase in the Arctic compared to other regions can be explained by the fact that energy (heat) is transferred from a larger area (heat source) to a smaller one (heat sink). In the summer half-year, the source area of radiative heat is 4.5 times greater than the sink area. As a result, the relative values of thermal energy (temperature) increase.

It is shown that based on the relationships between the patterns of the natural environment in the Arctic and the characteristics of its irradiation, it is possible to predict climate changes and the natural environment state in the Arctic on the basis of the characteristics of irradiation calculated for future time periods.