Milankovitch cycles (regarding ice ages on earth)

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Milankovitch cycles are long-term, natural variations in Earth's orbit and axial tilt that alter the amount of solar radiation reaching the planet, influencing long-term climate changes like the onset and end of ice ages. These cycles include changes in the shape of Earth's orbit (eccentricity), the tilt of Earth's axis (obliquity), and the wobble of Earth's axis (precession). These cycles operate over thousands to hundreds of thousands of years, affecting climate patterns by influencing seasonal solar radiation, not the total amount of solar radiation received. 

Here are the three main cycles:

Eccentricity:
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This is the variation in the shape of Earth's orbit around the Sun, from nearly circular to more elliptical. The average cycle length is about 100,000 years, though it can be closer to 96,000 or 405,000 years. 

Obliquity:

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This is the change in the tilt of Earth's axis. The tilt varies between approximately 21.5 and 24.5 degrees over an average of about 41,000 years. Greater tilt results in more extreme seasons, while less tilt leads to milder seasons. 

Precession:

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This is the wobble or "wobble" of Earth's axis of rotation. It causes the timing of the solstices and equinoxes to shift, changing which part of the orbit is closest to the Sun. The cycle length is roughly 23,000 years. 

Role in Climate:

Insolation Changes:
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These cycles cause quasi-periodic changes in the amount of solar radiation (insolation) reaching Earth, particularly in the mid-latitudes. 

Ice Ages:

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Changes in the tilt and precession can lead to cool summers that prevent snow and ice from melting, allowing glaciers and ice sheets to grow, which is a key factor in initiating ice ages. 

Long-Term Climate Driver:

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The combined effects of these three cycles provide a framework for understanding the long-term, natural fluctuations in Earth's climate over millennia. 

Distinguishing from Current Warming: 

It is important to note that Milankovitch cycles cannot explain the rapid global warming observed in recent times. The warming trend over the past century is far too fast to be driven by these slow orbital changes. The significant increase in atmospheric greenhouse gases from human activity is the primary driver of current warming, not the Sun or Earth's orbital position.

• Milankovitch (Orbital) Cycles and Their Role in Earth's Climate - NASA Science

  Feb 27, 2020

  

  NASA Science

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Why Milankovitch (Orbital) Cycles Can't Explain Earth's Current Warming - NASA Science

Feb 27, 2020

NASA Science

Milankovitch Cycles, Paleoclimatic Change, and Hominin Evolution | Learn Science at Scitable

The three elements of Milankovitch cycles are eccentricity, obliquity, and precession (Figure 3). Eccentricity describes the degre...

Nature