One of Milutin Milankovic's three big factors in his ice age theories was Earth's obliquity, or axial tilt. Earth's axial tilt varies between 22.1 and 24.5 degrees at an approximation of 41,000 years.

In this alternate Earth, the tilt varies between 20 and 25 degrees at an approximation of 61,500 years. How greatly would this affect the Earth's climate?

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    $\begingroup$ Making a question title clever is fine - so long as it also describes the question enough that people know whether they are interested in it or not. $\endgroup$ – Tim B Sep 6 '15 at 19:52
  • $\begingroup$ I can't speak for the downvoter's but it's likely that's where they came from as the question itself isn't terrible. People with no interest or opinion on axial tilt should not need to click on the question to find out if it interests them. $\endgroup$ – Tim B Sep 6 '15 at 20:09
  • $\begingroup$ It's an extremely complex question to answer, but most likely you would still have a habitable planet (i.e. without snowball-Earth or runaway greenhouse gas scenarios). You would have much hotter summers, much colder winters, and a wide range of other climatic effects. Please read this paper for some guidance of what different obliquities would do for an Earth-like planet according to simulations. $\endgroup$ – fantasia Sep 6 '15 at 21:29

It depends. Your world has a less stable axial tilt. It means that on the long term, you will have more frequent and more extreme temperatures. If the tilt is close to 23.4°, then the energy received at each latitudes will be the same as on Earth.

If you increase the tilt, hight latitudes in the north receive more energy in summer and less in winter, vice-versa for the south. the temperature variation would be stronger inland that on the coasts because water takes longer to accumulate/lose energy, while land can heat up very quickly. If you look at these images, you can see that the different zones move according to the seasons. With a bigger tilt, this change is more drastic. Compressing the Polar cell even more in the hot season. It makes the areas prone to monsoon larger in summer but also make drier weather conditions in winter: the expansion of the Polar cell in winter and the colder temperatures makes high pressure (dry) system more likely.

With a smaller tilt, you reduce the extremes. This mean more temperate temperature in mid and extreme latitudes with little impact between the tropics. Back to these images, reduce the variation of each zone to get an idea where the wet and dry areas will be. In this world, it is possible for India and China to be too cold to actually trigger the Asian monsoon, turning India into a much drier place.

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