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 23.44Ëš off the vertical axis.
  • This tilt varies with time, following a 41,000 year cycle.
  • At the maximum, the tilt is 24.5Ëš. At the minimum, it is 22.1Ëš. 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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