Eccentricity

Eccentricity describes the shape of the Earth’s orbit.

It ranges from the orbit being almost a perfect circle to being an oval, and returns to nearly circular shape. It takes 100,000 years for the orbit to accomplish such cycle.

Image source: NASA

In winter the orbit is nearly circular with Earth being a bit closer to the Sun in January than in July. Therefore, at this point in time, the orbit’s eccentricity has very little effect on the planet’s climate during a year. However, if the orbit was a pronounced oval, eccentricity would be a dominant factor affecting the climate, with Earth being warmer when it was closer to the Sun. The difference between the seasons would also be more pronounced.

Source: NASA