Milankovisyklit

Milankovitch cycles, named after the Serbian astronomer Milutin Milanković, refer to variations in Earth’s orbital geometry and axial rotation that alter the distribution of solar radiation (insolation) reaching the planet. These cycles constitute a primary form of orbital forcing that helps drive long-term climate changes, including glacial and interglacial periods, on timescales of tens to hundreds of thousands of years.

The three main components are:

- Eccentricity: changes in the shape of Earth’s orbit around the Sun, varying on roughly 100,000-year timescales, with a longer ~413,000-year modulation. This alters the total annual insolation, though its effect on seasonal contrasts is modest.

- Obliquity (axial tilt): the angle between Earth’s axis and its orbital plane, oscillating about 22.1 to 24.5 degrees over ~41,000 years. This modulates the seasonal contrast, especially at high latitudes.

- Precession: the wobble of Earth’s axis, shifting the timing of seasons relative to the orbital position, with a period of about 23,000 years. This affects which hemisphere experiences summer at perihelion and influences insolation patterns.

Their combined effect changes the distribution of sunlight across latitudes and seasons, influencing the growth and retreat of ice sheets. In the Quaternary, orbital forcing interacts with greenhouse gas concentrations and ocean–atmosphere dynamics, shaping the pace and pattern of climate cycles. While Milankovitch forcing is a major driver of long-term climate variability, it operates together with feedbacks and internal variability, so it is not the sole determinant of climate change.