Ultimately, this scenario will depend on whether or not this alternate Earth would orbit one G-type star or two, and whether dawn would still be in the east, like back home, or in the west, like in Venus. But for now, let's assume that this alternate Earth orbits one G-type star at a distance of 93 million miles. The one difference is this--the axial tilt varies between 19.7 and 26.9 degrees over a cycle of 122,000 years. Here is the map:

enter image description here

It's not much, so here is how it looks in comparison to our map, out of respect for how climate changes with latitude:

enter image description here

It still does not say much, I know, so I have sealed the deal with a mountain ranges map:

enter image description here

The ranges vary in height above sea level from 5,885 to 8,848 meters. The arrows indicate the directions in which the mountains are rising, therefore the landmasses are colliding with each other. It's reasonable to believe that behind each plateau comparable to Tibet.

In the event that one of you would be asking about atmosphere, since it does play a part in climate, too, oxygen makes up one-third of the atmosphere and there are 4500 parts per million of carbon dioxide.

So with all the information listed above, what would the climate of this alternate Earth be like?

(I'm not looking for all the Koppen complexities, just something more basic.)

  • 1
    $\begingroup$ This is a "truth or lipservice" kind of question. Any answer would have to embrace the reality that, with two suns, the right answer is "whatever you think it is." You need to tell us what you're trying to accomplish. $\endgroup$ Commented Oct 30, 2022 at 6:00

2 Answers 2


Your planet would be hot. Quite hot.

With 30% O$_2$ and 4500 ppm CO$_2$ you've essentially married the conditions of the Cretaceous Thermal Maximum, one of the warmest periods of our planet's history when global temperatures averaged up to 35°C and the poles were ice-free cool temperate regions, and the Cambrian greenhouse period, when CO$_2$ levels were around 4000 ppm and global temperatures averaged 22°C (with high latitude seas exceeding 20°), much warmer than today's average of about 15°C.

This study into the paleoclimate abstracted the Late Cretaceous climate as follows:

Abstract of Late Cretaceous climate

Using Artifexian's guide to climates on hot planets I've estimated your climate to the following:

Estimated climate map

Some notes:

  • I've averaged your axial tilt to 23.3°, which is barely distinguishable from Earth's. You may want to watch the above video for the impact tilt can have on deserts at perihelion and take that into account.

  • Wind and ocean currents are generalized.

  • Your equatorial mountain range devastates the tropical belt.

  • The net effect of the two parallel mountain ranges is rainshadows feeding rainshadows; that northern desert isn't going to see rain for centuries.

  • I may be overgenerous with the extent of the southern humid continental region, it would probably be a narrow, patchy strip along the coast, moreso at the western extent than the southern or eastern.

  • Likewise I've used the onshore prevailing wind of the northern Ferrel cell to justify the more southern extent of the northern humid continental region, as it would bring moist, humid air inland.


Here are an approximation of your prevailing winds from orbital motion: enter image description here

I've basically taken the diagram from Wikipedia's prevailing winds, the red lines match the lines on the globe diagram.

From this prevailing winds diagram, you can follow the same process I did on What climates can I expect on my fictional continent?

The affect of the tilt of basically 28 degrees is gone into here How to Determine Planetary Extremes of Temperature from Average Global Temperature?, you're going to get very cold winters and very hot summers, and most of that top detailed coastline will not see much sun for months.

  • $\begingroup$ How did you get five cells, and so varied in size? $\endgroup$
    – rek
    Commented Sep 24, 2020 at 2:00

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