But why is it so hot?

July 2023 is set to become the hottest July on record, according to the European observatory Copernicus. Why is this?

For millennia, the Earth has alternated between warm periods and ice ages. Scientists have finally cracked the secret behind this climatic phenomenon. Recent research has revealed that these climatic variations are closely linked to our planet’s orbital parameters around the Sun. A discovery that highlights the crucial role played by astronomy in the Earth’s climate. It is the work of Serbian astronomer Milutin Milankovitch and Belgian meteorologist André Berger, who have confirmed the influence of orbital variations on climate change.

The eccentricity of the Earth’s orbit

The Earth’s orbit is not a perfect circle, but an ellipse. This variable eccentricity is responsible for climate variations over periods ranging from 90,000 to 400,000 years. The greater the eccentricity, the longer the orbit, resulting in fluctuations in the solar energy received by the Earth on its journey around the Sun.

The inclination of the Earth’s axis of rotation

The Earth's rotation axis describes a cone in 25,800 years (Wikipedia)
The Earth’s rotation axis describes a cone in 25,800 years (Wikipedia)

The tilt of the Earth’s axis in relation to its orbit is responsible for the existence of the seasons. This inclination varies over a period of around 41,000 years. The more the axis is inclined, the greater the contrast between seasons. Variations in this inclination have a significant impact on our planet’s climate.

The precession of the equinoxes

The phenomenon of precession causes the Earth’s axis of rotation to describe a cone in about 25,800 years. This slow movement influences the position of the solstices and equinoxes in relation to the orbit around the Sun. The period associated with the precession of the equinoxes is around 21,000 years, and also plays a key role in climatic variations.

The determining combination

Orbital variations, though powerful, are not enough on their own to trigger glaciation. It is their combination that is crucial. An ice age can begin when the Earth’s eccentricity is at its maximum, the axis of rotation is slightly inclined and the summer solstice is at aphelion. This configuration makes the Earth more susceptible to ice ages.

Towards a prolonged interglacial?

The current interglacial is likely to last longer, due to the current low influence of orbital parameters on glaciation. However, there is another factor at play: anthropogenic greenhouse gas emissions. These emissions are considerably modifying the composition of the atmosphere, and could further delay a future ice age.

An astronomical legacy

The connection between orbital variations and climatic periods is a recent discovery. However, it is based on earlier astronomical discoveries and advanced mathematical calculations by eminent scientists such as Hipparchus, Kepler, Newton, Euler, Lagrange, Laplace and others. Paleoclimatologists have also played a crucial role, using geological data to validate these models and study the evolution of temperatures over long periods.


The discovery of the influence of the Earth’s orbital variations on ice ages and warm periods represents a giant step forward in our understanding of the Earth’s climate. The work of Milankovitch and Berger has demonstrated the importance of astronomy in shaping our climate. As we continue to explore the mysteries of our planet, it is essential to take these orbital parameters into account in our climate forecasts to better anticipate our planet’s future.
Human activity alone does not explain the catastrophic climate change we are experiencing.

Sources : 1 , 2 et 3