Post by Stealth Tuba Post by Jan Panteltje
In reality climate change is caused by orbital changes that cause changes
in earth exposure to the sun, see kooksite
If something is changing the Earth's orbit in a short period of time, we
have a lot bigger problem than climate change.
Tip: precession affects the Earth's rotation, not the orbit. Don't depend on
kooksites for science.
Milanovitch cycles involve variations in the earths orbit. These
variations last tens of thousands of years and, therefore, have little
effect in the short run. There are attempts to link these cycles with
ice ages, but as yet these attempts are not regarded as highly
Keep in mind that Milanovitch cycles involve season changes due to the
state of the Earth in its journey around the sun. They do not involve
differences in the output energy of the sun.
There are three main cycles brought about by eccentricities in the
orbit of the Earth around the sun. These cycles last
approximately 21,700 years (cycle due to precession),
approximately 41,000 years (cycle due to axial tilt),
and approximately 95,800 years (cycle due to orbital eccentricity or
These cycles have not been reliably linked to long-term climate.
These differences are not thought to be great enough to do more than
marginally alter the amount of energy reaching the earth from the sun.
To claim any effect on earth climate, it is necessary to suggest
feedback mechanisms such as, for instance, albedo changes from
marginally extra snow fall.
Ellipsicity effects the differences of heat distribution between
summer and winter. These differences range from around 6% at one part
of the cycle to maybe 25% during the most elliptical phases. We are
currently near to the part of least variation in the 95,800 years
cycle. That is, the least variation between winter and summer.
Axial tilt is currently about half way between its extremes of its
41,000 year cycle. This effects the contrast between the severity of
seasons. The part of the theory concerning axial tilt suggests that
less tilt may increase snow cover.
Precession is the wobble that can be seen with a spinning gyroscope or
top. This 21,700 year cycle moves the winter and summer peaks closer
to or further from equilibrium. We are currently in the equilibrium
part of the cycle.
Vostok tells us a story of mostly glaciation for the last 400,000
years, with short interglacial periods of up to 20,000 years, very
roughly every 100,000 years. (This is part of the reason so many have
tried to fit the Milankovitch data to weather.) The recent
interglacial period has already lasted around 10,000 years. There was
a dip starting around 700 years ago which appears to have started to
reverse at about 1800 AD. In other words, we do not know quite why the
weather swings over the eons, but we do suspect that we are due to go
into another ice-age at any time.
This 100,000 years cycle has recently replaced a much shorter cycle,
some claim that that earlier cycle was around 40,000 years.
[Note that the Moon also wobbles in its orbit, affecting the height of