The Climate, Environment and Energy Thread

[LP]

    how much Earth is tilted relative to the Sun
    whether Earth wobbles a lot or a little as it spins on its axis (kind of like how a toy top can wobble a lot or a little as it spins)
    the shape of Earth's orbit as it goes around the Sun (whether it is shaped more like a circle or more like an ellipse or oval)

[member=105]Thryleon[/member]  This bit is a horribly simplistic hash up between what causes the seasons and what influences long term climate change.

The shape of the earths orbit effectively doesn't vary at all on times scales measured in billions of years, it's almost perfectly round less than 3% elliptical. The Sun's changing flux over that time has far more influence than any small orbital variations but even that solar flux variation is trivial on human time scales.

The earth wobbles (Precession) but this has no long term effect as it is cyclic, and the same applies in regards to the tilt. Small timing variations causing correlations between precession and Earth's position in it's elliptical orbit can cause some slight longer term seasonal variations. This is because a conjunctions between the perihelion, aphelion and precession.

The seasons are cyclic because they are caused by the tilt, the Earth is effectively a big spinning gyroscope pointing mostly in the same direction with a slight precession. But Earth's precession takes 26000 years to complete. Interestingly, the main climate effect of precession is modelled to be an evening out of the seasons mid-cycle, not a change in the averages, at some stage in the 26000 cycle summer and winter would be barely distinguishable around the equator. There is no history of glacial or inter-glacial periods tide to precession, even the Maunder Minimum has been ruled out as a precession effect.

A nice debunking argument for the climate change sceptics who try to claim orbital dynamics is the cause, is that the Earth is closest to the sun(About 5,000,000 km closer) when the Northern Hemisphere is in the middle of it's winter.