Summer has passed


in Daily updates, Geek stuff, Science, The environment

Some facts for the autumnal equinox:

  • The Earth has seasons because it orbits the sun while tilted 23.44˚ off the vertical axis.
  • This tilt varies with time, following a 41,000 year cycle.
  • At the maximum, the tilt is 24.5˚. At the minimum, it is 22.1˚. When there is more tilt, the difference between summer and winter increases. When there is less tilt, the seasons are more similar.
  • Along with the changes in the shape of Earth’s orbit (eccentricity – 100,000 year cycle) and the way the planet wobbles around the pole (precession – 26,000 year cycle), axial tilt (obliquity) contributes to the Milankovitch cycles – one of the major long-term drivers of natural climate change.
  • To learn more, look up Dansgaard-Oeschger events and Heinrich events.

Disclaimer: Yes, orbital and solar variations affect the planet’s climate. That doesn’t mean human greenhouse gas emissions don’t, nor that they aren’t the primary cause of the climate change presently taking place!

{ 2 comments… read them below or add one }

AnonymousClassicist September 22, 2008 at 10:30 pm

You sir are wrong and a fool! We have seasons because Persephone was kidnapped by Hades. That crime so disheartened Demeter that she refuses to make things fruitful for a span of months equal in number to the pomegranate pips her daughter consumed in the underworld.


Milan September 22, 2008 at 10:43 pm

That is all very true, but you forget that Demeter’s wrath caused the axial tilt.

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