What effect does the tilt of the earth have?

Earth’s spin, tilt, and orbit affect the amount of solar energy received by any particular region of the globe, depending on latitude, time of day, and time of year. Small changes in the angle of Earth’s tilt and the shape of its orbit around the Sun cause changes in climate over a span of 10,000 to 100,000 years, and are not causing climate change today.

Daily changes in light and temperature are caused by the rotation of the Earth, and seasonal changes are caused by the tilt of the Earth. As the Earth orbits the Sun, the Earth is pulled by the gravitational forces of the Sun, Moon, and large planets in the solar system, primarily Jupiter and Saturn. Over long periods of time, the gravitational pull of other members of our solar system slowly change Earth’s spin, tilt, and orbit. Over approximately 100,000 – 400,000 years, gravitational forces slowly change Earth’s orbit between more circular and elliptical shapes, as indicated by the blue and yellow dashed ovals in the figure to the right. Over 19,000 – 24,000 years, the direction of Earth’s tilt shifts (spins). Additionally, how much Earth’s axis is tilted towards or away from the Sun changes through time, over approximately 41,000 year cycles. Small changes in Earth’s spin, tilt, and orbit over these long periods of time can change the amount of sunlight received (and therefore absorbed and re-radiated) by different parts of the Earth. Over 10s to 100s of thousands of years, these small changes in the position of the Earth in relationship to the Sun can change the amount of solar radiation, also known as insolation, received by different parts of the Earth. In turn, changes in insolation over these long periods of time can change regional climates and the length and intensity of the seasons. The Earth’s spin, tilt, and orbit continue to change today, but do not explain the current rapid climate change.

Adapted from Universe Today.

Changes in insolation result in cycles of ice ages, during which ice sheets expand (glacial periods) and contract (interglacial periods). These patterns of ice ages, also called Milankovitch cycles, were predicted by the Serbian scientist Milutin Milankovitch. Milankovitch predicted that glacial periods occur during times of low summer insolation at high latitudes in the northern hemisphere, which would allow ice sheets to remain from year to year without melting. Subsequently, scientists have found extensive evidence of Milankovitch cycles preserved in the geologic record, especially in layers of sediment and fossils in ocean basins that preserve chemical changes in the ocean and atmosphere during glacial and interglacial periods.  Although a major cause of change over long periods of time in the past, Earth’s spin, tilt and orbit changes so slowly that it is not a cause of global warming and climate change today.

Changes in Earth’s spin, tilt, and orbit have affected the Earth system in the past on various scales. Some of these ways include:

• Increasing or decreasing amount of sunlight that is absorbed by different areas of the surface of the Earth. This can affect Earth’s temperature.
• Increasing or decreasing temperatures, which can alter the distribution of snow and ice cover. By increasing snow and ice cover, especially at high latitudes, the reflection of sunlight can increase, which in turn decreases the amount of light that is absorbed by Earth’s surface.
• Changes in the Earth system that are affected by snow and ice cover, including the carbon cycle, and how much carbon (including the greenhouse gas carbon dioxide) is transferred between the atmosphere, biosphere, and ocean.

Visit the solar radiation and Earth’s energy budget pages to learn more about how changes in the amount of energy in the Earth system can affect global processes and phenomena.

Links to Learn More

Updated April 24, 2017

By Eric Moll

Earth's axis is tilted by approximately 23.5 degrees. In other words, Earth's daily rotation is shifted by 23.5 degrees with regard to its yearly revolution around the sun. This axial tilt is the reason why Earth experiences different seasons throughout the year, and also why summer and winter occur opposite each other on either side of the equator -- and with greater intensity farther away from the equator.

The sun burns with the same intensity all year. Earth's elliptical orbit brings it closer or farther at different times of year, but this change in distance has a negligible effect on weather. The important factor is the incident angle of sunlight. As an example, imagine that you have a flashlight and a piece of paper. Hold the paper so that it is perpendicular to the beam of the flashlight, and shine the light on the paper. The light hits the paper at 90 degrees. Now, tilt the paper. The same light is spread over a larger area, and is therefore much less intense. The same phenomenon occurs with Earth and the sun.

The reason the equator is the hottest part of the planet is because its surface is perpendicular to the sun's rays. At higher latitudes, however, the same amount of solar radiation is spread over a larger area, due to Earth's spherical shape. Even without any tilt, this would result in the equator being warm and the poles being cold.

Because Earth is tilted, different latitudes receive different sun angles throughout the year. During summertime in the Northern Hemisphere, Earth is tilted so that the Northern Hemisphere is angled more directly at the sun. It receives more direct sunlight and is warmer. At the same time, the Southern Hemisphere is angled away from the sun, so it receives less direct sunlight and experiences winter. The axial tilt doesn't change throughout the year, but as Earth travels to the other side of the sun, the opposite hemisphere is angled toward the sun and the seasons change.

At the fall and spring equinoxes, in mid-September and mid-March, the axis is pointed neither toward nor away from the sun, and the Northern Hemisphere and Southern Hemisphere receive the same amount of sunlight. Day and night are of equal length at these times. After the equinox, the days begin to get shorter in one hemisphere and longer in the other. At the summer and winter solstices on the 21st or 22nd of June and December, the days are at their longest or shortest, respectively. The summer solstice in the Northern Hemisphere, June 21st or 22nd, is also the winter solstice in the Southern Hemisphere, and vice versa.