This is what scientists are supposed to do, find inconsistencies, point them out, and put them right. And so I gave this a little thought.
A favourite teaser in TV and radio quiz programs is to ask contestants which nation contains the point furthest from the Earth’s centre. Most people think the questioner is referring to Mount Everest, but those with a little more knowledge imagine that any difficulty in giving a definitive answer is due to the peak of that mountain forming part of the border between Nepal and Tibet, with the additional complication that the latter is claimed by China. All are wrong.
In fact the correct answer is Ecuador, and the mountain in question is an inactive volcano called Chimborazo. Not far behind is a peak in Peru named Huascarán, which is actually taller than Chimborazo, compared to mean sea level; but the Ecuadorian volcano wins by dint of being closer to the equator. Mount Everest is nowhere near these two, in terms of distance from the centre of the Earth, being more than two kilometres below.
The above may seem confusing, but it’s quite simple, really. Our planet is not spherical in shape, with the difference between the equatorial and polar radii being more than 21 kilometres. Mountains nearer the equator may have lower heights measured above mean sea level but the sea, like the planet as a whole, has an overall shape best described as a geometrical form known as an oblate spheroid.
The World Geodetic System defines a standard geoid or Earth shape for mapping and navigation that is referenced as WGS 84. This is what is used, for example, by the Global Positioning System (GPS), by which many of us navigate when driving. This geoid is an ellipsoid of revolution such that the equator is a circle with radius 6378.137 km, but polar flattening means that the distance from the Earth’s centre to either of the poles is only 6356.752 km.
Of course these figures represent only a convenient, usable model, and the mountains mentioned earlier (along with Slartibartfast’s other “lovely crinkly edges”) mean that we all recognise it’s only an approximation which may or may not be good enough, depending on what you are wanting to do, precisely. But the Earth is most definitely not a sphere.
What has this to do with the climate? you might ask. My answer follows.