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Causes: Milankovitch Cycles

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The Milankovitch Cycles

Summary

  • Changes to Earth’s climate over long periods are caused by the natural variations in intensity and distribution of solar radiation that reaches the planet.
  • Today, when the Milankovitch Cycles are taken into consideration, Earth should have been slowly cooling over the past 9,000 years. Instead, we’re warming (Fig. 1 & Video 2).
  • This gradual warming was because people developed agriculture. On balance, the climate remained relatively stable until the Industrial Revolution in the 1800s when we started burning huge amounts of fossil fuels. This rapid anthropogenic (man-maded) forcing rapidly outweighed the gradual cooling effects from the Milankovitch Cycles.
  • These cycles are because Earth’s orbit around the Sun is eccentric (Fig. 2), it’s axis is tilted (Fig. 3), and it wobbles (Fig. 4), each over different time frames or cycles (Fig. 5).
  • The cycles are named after the geophysicist and astronomer Milutin Milanković, who developed James Croll’s theory that these cycles were the main climate change forcings (Video 1).
Fig. 1: The day grey line shows the observed temperature changes for the past 125 years, while the pale blue line shows Earth’s orbital changes. The cooling influence of the Milankovitch Cyles over the past 9,000 is hardly noticeable in this short time frame. (Credit: Bloomberg)

Home > Climate wiki > What causes climate change? > Milankovitch Cycles

The Milankovitch Cycles

Summary

  • Changes to Earth’s climate over long periods are caused by the natural variations in intensity and distribution of solar radiation that reaches the planet.
  • Today, when the Milankovitch Cycles are taken into consideration, Earth should have been slowly cooling over the past 9,000 years. Instead, we’re warming (Fig. 1 & Video 2).
  • This gradual warming was because people developed agriculture. On balance, the climate remained relatively stable until the Industrial Revolution in the 1800s when we started burning huge amounts of fossil fuels. This rapid anthropogenic (man-maded) forcing rapidly outweighed the gradual cooling effects from the Milankovitch Cycles.
  • These cycles are because Earth’s orbit around the Sun is eccentric (Fig. 2), it’s axis is tilted (Fig. 3), and it wobbles (Fig. 4), each over different time frames or cycles (Fig. 5).
  • The cycles are named after the geophysicist and astronomer Milutin Milanković, who developed James Croll’s theory that these cycles were the main climate change forcings (Video 1).
Fig. 1: The day grey line shows the observed temperature changes for the past 125 years, while the pale blue line shows Earth’s orbital changes. The cooling influence of the Milankovitch Cyles over the past 9,000 is hardly noticeable in this short time frame. (Credit: Bloomberg)
Fig. 2: Earth’s eccentric orbit around the sun (100,000 year cycle). When Earth is further away from the sun it receives less solar energy and therefore less warmth.
Fig. 3: Earth is slightly tilted (40,000 year cycle). As most of the land mass is now in the Northern Hemisphere (see the link in the menu ‘How to start an ice age’), when less of that hemisphere is facing the sun in winter, it receives less warmth.
Fig. 4: Precession (26,000 year cycle). This wobble can either add to the cooling or warming depending on which phases of the other two cycles that Earth is in (Figures 1 and 2).
Fig. 5: Each cycle occurs over different time frames. When they coincide, the effects are multiplied. Factors such as plate tectonics (see Video 1) and the balance of the carbon cycle can exaggerate, reduce, or cancel the effects of the Milankovitch Cycles over thousands or millions of year. (Image: The Nature Education Project)

Video 1: The Milankovitch Cycles are changes in the Earth’s orbit and rotation that cause the Earth’s climate to change over hundreds of thousands of years.
Video 2: This follow up video explains where we are within the cycles now and how this relates to greenhouse gases.

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