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How does orbital eccentricity affect the amount of solar radiation Earth receives?

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Map showing the extent of the Laurentide, Cordilleran, and Greenland ice sheets during the Wisconsin glaciation, roughly 100,000 to 11,000 years ago. The Laurentide Ice Sheet covers most of present-day Canada and parts of the northern United States in light blue, the Cordilleran Ice Sheet covers the Pacific Northwest in teal, and the Greenland Ice Sheet is marked in purple. Modern international and state or provincial boundaries are outlined for reference. — Pleistocene Epoch Ice sheets during the Wisconsin glacial episode penetrated deep into North America.

Orbital eccentricity refers to the shape of Earth’s orbit around the Sun, which fluctuates between nearly circular and more elliptical over cycles of approximately 100,000 and 413,000 years. This parameter is one of three Milankovitch cycles that influence the distribution of solar radiation across the planet's surface.12

When Earth’s orbit becomes more eccentric (more elliptical), the distance between Earth and the Sun varies more significantly throughout the year. This variation alters the amount of solar energy received at different latitudes and seasons. While eccentricity is considered the weakest of the three orbital parameters in terms of direct radiation impact, it is recognized as a primary "pacemaker" for the Pleistocene glacial-interglacial cycles.23

Scientists hypothesize that these orbital changes, combined with feedback mechanisms like albedo and atmospheric carbon dioxide fluctuations, drive the cooling and warming trends that characterize Earth's climate history.2