If the Earth’s axis was perpendicular to its orbital plane (no tilt), there would be no seasons and the weather would be much more extreme and consistent.The equator would be permanently hot with the sun directly overhead, while the poles would be permanently frigid with little to no sunlight, leading to growing polar ice caps. This would result in a drastically stratified climate, with severe temperatures and weather patterns moving from the equator to the poles, potentially leading to mass extinctions and changes to the Earth’s ecosystems.

Summer–Autumn–Winter–Spring

Eccentricity measures how much the shape of Earth’s orbit departs from a perfect circle. These variations affect the distance from Earth to Sun. Obliquity The angle Earth’s axis of rotation is tilted as it travels around the Sun is known as obliquity. Obliquity is why Earth has seasons. Over the last million years, it has varied between 22.1 and 24.5 degrees with respect to Earth’s orbital plane. Precession of the equinoxes, motion of the equinoxes along the ecliptic (the plane of Earth’s orbit) caused by the cyclic Precession of the Earth’s axis.

The winter Solstice marks the moment the Earth’s South Pole reaches its furthest tilt away from the Sun. During the Southern Hemisphere’s June, or winter, Solstice, the Sun appears at its lowest point in the sky, marking the shortest day of the year and longest night,” explains astronomy expert Glenn Dawes. “During the Solstice, Earth’s Southern Hemisphere is tilted away from the Sun, while at the same time the Northern Hemisphere is tilted towards it, resulting in the longest day of the year there. “The word “Solstice” comes from the Latin sol (sun) and sistere (to stand still), because the Sun was believed to stand still for a moment before changing direction.

Below: The Mid-Cretaceous era was the heyday of the dinosaurs but was also the warmest period in the last 149 million years, with temperatures in the tropics as high as 35 C and sea levels 170 metres higher than today. In the months of darkness, swampy temperate rain forests were able to grow close to the South Pole, revealing an even warmer climate than what it had previously been.To get these conditions, scientists believe that 90 million years ago the Antarctic continent was covered with vibrant and dense vegetation and there were no land-ice masses on the scale of an ice sheet. The work also suggests that the carbon dioxide (CO2) levels then were higher than expected during the mid-Cretaceous period, 115-80 million years ago, challenging  the previous climate models for that period. “Before our study, the general assumption was that the global carbon dioxide concentration in the Cretaceous was roughly 1,000 parts per million (ppm),” according to Geoscientist Torsten Bickert from the University of Bremen in Germany. “But in our model-based experiments, it took carbon dioxide concentration levels of up to 1,680 ppm to reach the average temperatures back then in the Antarctic.”