Milutin Milankovich, a Serbian mathematician, astronomer, and
engineer solved the mystery of what caused major ice ages over the
last half-million years of Earth's history. He showed that regular
changes in Earth's orbit result in periods of lower global
temperature, and these periods correspond to the timing of past ice
ages.
Explore the visualization yourself, or follow the instructions
below to help you understand how changes in three orbital parameters
have affected global temperature.
Faster Orbit
Orbital Parameters:
Check out the controls
Click several combinations of the top six buttons to see how they
control the animation.
Click and drag the yellow triangle (time slider) to display
conditions at different times.
If you need definitions for any of the labels that appear in
the animation, enter the words in an Internet search
engine.
Explore each of the three orbital parameters:
Eccentricity
Select Top View and Orbit.
From Orbital Parameters, click Eccentricity (only).
Drag the time slider up and down to see the shape of Earth's
orbit at different times. Eccentricity is a measure of how circular an
orbit is
The magenta line in the graph shows how global temperature would
change if eccentricity were the only orbital parameter that
changed.
Precession
Select Oblique View, Rotation, and Orbit.
From Orbital Parameters, click Precession (only).
Drag the yellow slider up and down fairly slowly to see the motion
of precession. Have you seen that motion before? Some people recognize
it as the wobble of a spinning top.
To see the effect precession has on Earth, go to Top View, set the
animation to your favorite season, click season lock, and move the
time slider up and down again.
The result of precession is that solstices and equinoxes occur at
different locations in the orbit, and this changes the season that is
occurring when Earth is closest to and farthest from to the Sun.
The magenta line shows how global temperature would change over
time if precession were the only orbital parameter that changed.
Tilt
Select Oblique View. Use Faster Orbit to move Earth directly to
the right or left of the Sun, then click Orbit.
From Orbital Parameters, click Tilt (only).
Drag the time slider up and down to see how the angle Earth's
axis makes with its orbital plane changes over time.
The magenta line shows how global temperature would change over
time if the tilt of Earth's axis were the only orbital parameter
that changed.
C. Compare all orbital parameters to Earth's past
temperature.
Click Vostok Ice Core.
The green line in the graph shows scientific estimates of global
temperature for the last 400,000 years. Temperatures are based on the
ratio of light and heavy oxygen atoms in layers of ice in a core
drilled from Vostok Station in Antarctica.
Click various combinations of Eccentricity, Precession, and Tilt
to see how global temperature is affected by these orbital parameters.
Which combination of orbital parameters do you think produces the
best match with temperatures derived from the Vostok Ice Core?
If global temperature were only controlled by orbital parameters,
how would you expect global temperature to change in the future?
