Milankovitch Cycle Historical Climate Change During warm interglacial

Milankovitch Cycle Historical Climate Change

• During warm, interglacial periods denoted by the grey bars, the concentrations of greenhouse gases, CO 2 and CH 4, were higher than during the colder, glacial periods.

Earth’s Natural Climate Change • Interglacial periods occur about every 100, 000 years. • Why do these glacial and interglacial changes occur?

Earth Orbit

Eccentricity, Spherical • 100, 000 years • Max to Max

Obliquity, Axial Tilt Varies from about 22° to 25° Period of about 41, 000 years.

Precession, Wobble Precession period of about 20, 000 years.

Why do times of glaciation occur episodically on Earth?

Milankovich Cycle 3 things change within Earth’s motion • 1 - The Eccentricity of the Earth’s orbit varies just slightly from one maximum to the next every 100, 000 years. • Eccentricity is at its maximum = Earth is closest to the sun. • 2 - The angle of tilt, the obliquity, varies from about 22° to 25° with a period of about 41, 000 years. • 3 - Like a large wobbly spinning top, the Earth’s rotation axis precesses with a precession period of about 20, 000 years.

Orbital Forcing • About every 100, 000 years. • When all 3 variations occur at the same time warming begins. • The end of an ice age coincides with the times when the northern hemisphere 1. tilts toward sun at high obliquity 2. the orbital eccentricity is at a maximum 3. the Earth is closest to the sun during the northern hemisphere summer.

So what’s the big deal about climate change? What’s different now?

Group Activity • Draw a picture that shows the Earth in orbit and accounts for all aspects of the Milankovitch cycle. • Label the 3 parts and how they can vary. • Indicate on the drawing when an interglacial period is triggered.