Why is the South Pole Colder than the North Pole?

I remember this question from my childhood:

Why is the South Pole colder than the North Pole?

Indeed, the average winter temperature at the North Pole of -34°C is the same as the temperature at the South Pole at the beginning and end of its summer. The South Pole is only warmer than the North Pole 40 days per year. So the South Pole is a much, much colder place. According to Wikipedia there are three major reasons for this:

  1. The North Pole is at sea level, while the South Pole is elevated to almost three kilometers. The higher a land mass the colder it is.
  2. The North Pole sits on water whose temperature never goes below -2°C. Compared to the South Pole, this is like keeping the North Pole on the stove top.
  3. The South Pole is farther from the ocean, so it has higher continentality, which is usually associated with colder temperatures.

I remember when I was a child my father gave me a completely different explanation.

The Earth’s orbit is not a circle, but rather an ellipse. According to Kepler’s second law: “A line joining a planet and the sun sweeps out equal areas during equal intervals of time.” This means that the earth has a slower angle motion around the aphelion — in its furthest point — than around the perihelion — in its closest point to the Sun. Consequently, the summer is longer than the winter for the North Pole, whereas the opposite is true for the South Pole.

Something in my father’s explanation bothered me. Now I understand what: though the summer is longer at the North Pole, it should get less sunshine as the North Pole is further away from the Sun than the South Pole during its summer. So the effects might cancel each other out. In any case, as the earth’s orbit is almost circular, the contribution of the shape of the orbit should be minor, compared to the effects of elevation, the water underneath and continentality.

On the other hand, it is possible that my father wasn’t talking about the poles, but rather about the difference in hemispheres. I wonder if someone can calculate if there is a difference in the amount of sunlight the poles get due to the fact that the Earth’s orbit is not circular. Is the temperature different for the places that are equidistant from the equator, and have similar elevation and continentality, but which are located in different hemispheres?

I remember a funny article explaining why the northern hemisphere has more land. They said that continents drifted into the northern hemisphere because they wanted a nicer climate.

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5 Comments

  1. Scott Farrar:

    I’m not sure about the orbital-influence, since large portions of the north and south poles go without sunlight entirely for weeks at a time. You may be interested in an applet I created for the Axis influence on the sunlight received. http://scottfarrar.googlepages.com/winter_solstice.html

  2. Random Blogreader:

    During the last ice age, the situation was reversed. Namely the earth was closest to the sun during the northern summer. The total amount of solar energy received was actually lower, which is what caused the huge northern hemisphere ice sheets to form. (Interestingly, the increased reflectivity of the earth due to these ice sheets actually ended out cooling the southern hemisphere too.)

    And if the arctic sea ice continues to melt, there will be dark sea water in the arctic, and reflective ice in the antarctic, which will only increase summer warmth in the arctic relative to the antarctic.

  3. Adrian Prince:

    We just did a trivia quiz which claimed there was more sunlight at the north pole than at the south pole. Does anyone have a definitive answer to the question? Please note that the question was about sunlight not daylight so the extent of cloud cover would come into it.

  4. xyron hernandez:

    that’s why aang got preserved

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