4 ms·
It’s more complex than either case. The eccentricity of earth’s orbit precesses, as well as earth’s axial tilt. In a circular orbit, the seasonal variation is
by madaxe_again 8y ago
It’s more complex than either case. The eccentricity of earth’s orbit precesses, as well as earth’s axial tilt.
In a circular orbit, the seasonal variation is driven solely by the axial tilt and relative hemispherical insolation bought about by earth’s own shadow, and angle of the sun to terrain.
With a variable distance from the sun, the seasons become erratic, as these two variables precess out of sync - you end up with winters in one hemisphere where the earth is close to the sun, making for mild winter and scorching summer in the other hemisphere. Equally you end up with the earth far from the sun, and bitter winters and cool summers. Finally, you have the precessions 180 degrees out of sync, and you end up with almost no seasonal variation.
So - it makes the overall swings far more extreme, but in some phases can result in milder seasons.
- Unkechaug 8y agoWhere are we now and where are we headed?
- mkempe 8y agoWe're headed to the end of the current interglacial, returning to a drastically cooler climate. The last interglacial (the Eemian [1]) lasted 15k years and was warmer than what we experience today; sea level at peak was probably 6 to 9 m (20 to 30 feet) higher than today; Scandinavia was an island. Then the glaciation returned for 100k years with mile-thick ice sheets covering huge parts of Europe and North America, until the current interglacial got going almost 12,000 years ago. [2] "The axial tilt varies between 22.1° and 24.5°, over a cycle of about 41,000 years. The current tilt is 23.44°, roughly halfway between its extreme values. The tilt last reached its maximum in 8,700 BCE. It is now in the decreasing phase of its cycle, and will reach its minimum around the year 11,800 CE. ... decreasing tilt may encourage the onset of an ice age ..." [3] [1] https://en.wikipedia.org/wiki/Eemian https://en.wikipedia.org/wiki/Eemian [2] https://en.wikipedia.org/wiki/Last_glacial_period https://en.wikipedia.org/wiki/Last_glacial_period [3] https://en.wikipedia.org/wiki/Milankovitch_cycles#Axial_tilt_(obliquity) https://en.wikipedia.org/wiki/Milankovitch_cycles#Axial_tilt...
- milankovic 8y agoThe simple truth is: No one really knows. How do you determine the exact position in a cycle of 400000 years?
- milankovic 8y agoOkay, then what is the exact position? Where are we in the cycle? Please enlighten me.. Even if we assume an observational error of just 1%, that is still +- 4000 years. 4000 years ago, the earth was still the center of the universe. Obviously.