The Milankovitch Cycles
In the eyes of Milutin Milankovitch, there’s been a noticeable trend in climate, temperature, and seasons due to this cycle. And we can accredit these long-term climate changes to 3 variations in geometry between the Earth and the sun:
- ECCENTRICITY: How the Earth orbits the sun.
- OBLIQUITY: What angle does Earth face the sun?
- PRECESSION: How Earth’s axis of rotation changes.
If you put these 3 interactions of Earth and the sun together, they form the Milankovitch Cycle. Let’s explore this in more detail.
1. Orbital eccentricity
Earth revolves around the sun in a roughly circular orbit. But roughly every 100,000 years, its orbit becomes more eccentric.
So it starts as a circular orbit like it is in its current state. But like a pendulum, the eccentricity will swing it back the other way with a more elliptical orbit.
Because Venus is so close to Earth, its gravitational interactions slightly pull Earth in its orbit. Then, colossal Jupiter pulls Earth slightly outside its orbit at the opposite end.
So Earth periodically goes from a circular orbit to a more elliptical one (high eccentricity). This is due to the gravitational pull of neighboring planets. Because of its orbital eccentricity, Earth varies in distance from the sun. As a result, it receives less solar radiation causing it to cool.
2. Obliquity variation
The next piece of the puzzle is obliquity. Right now, Earth’s obliquity is 23.5°. But during the Milankovitch Cycle, it varies from 22.1° to 24.5° and takes 40,000 years to complete a full cycle.
Earth’s changing obliquity doesn’t alter the total amount of incoming solar radiation. Instead, it affects the geographic distribution of where sunlight hits the Earth.
AXIAL TILT: For example, if axial tilt increases, winters are colder in both hemispheres. And vice versa for when axial tilt decreases.
In summary, more tilt signifies more severe seasons. For instance, this can cause long periods of glaciation. And for Earth as a system, it enters positive and negative climate feedback loops.
The effects are drastic for long-term climate change. And this is all because of Earth’s change in an axial tilt that gradually shifts every 40,000 years.
3. Axial precession
Axial precession is the movement of the rotational axis of Earth. According to the Milankovitch Cycle, precession has a cycle of roughly 23,000.
Precession occurs because the Earth is not a perfect sphere. It flattens out at the poles and widens at the equator. In addition, the gravitational pull from the sun and moon causes precession.
Similar to obliquity, precession doesn’t change the total amount of solar radiation that hits Earth. But precession primarily alters the perihelion and aphelion.
“Axial precession is the movement of the rotational axis of Earth. Overall, this increases the seasonal differences from one hemisphere to the other.”
What Are the 3 Milankovitch Cycles?
The Milankovitch cycles are a set of predictable, periodic changes in Earth’s orbit and axial tilt that influence the planet’s climate over long periods of time.
These cycles are thought to be responsible for variations in Earth’s climate, including ice ages and interglacial periods, as they affect the distribution of solar radiation received by the Earth’s surface.
Do you have any questions about the Milankovitch cycles? Please drop us a comment below and we’ll try to get back to you.