“Aphelion” is the point in space
where Earth is at its furthest distance from the Sun during its elliptical
orbit.
Earth reaches aphelion in early July each year. Conventional wisdom might suggest
that aphelion is where Earth is coldest, as it is approximately 5 million
kilometers further from the Sun than at “perihelion,” where Earth is nearest to
the Sun. The additional distance to the Sun results in 7% less sunlight
globally at aphelion than at perihelion.
But ironically, Earth at aphelion is on average 4 degrees
warmer than at perihelion. This is due to the greater land mass of the northern
hemisphere. Land absorbs heat faster than water. Aphelion is reached at a time
when longer days in the northern hemisphere permit more land to absorb heat for
more time each day, permitting Earth as a whole to capture more heat. Even a
distance of 5 million kilometers, in these circumstances, has little bearing on
Earth’s ability to soak up the Sun’s energy.
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