Cold weather has nothing to do with distance to the sun!

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

07 July 2024

The message saying that the present cold weather in Kenya is due to the earth moving too far away from the sun has started circulating again on the WhatsApp platform. If you come across it, ask yourself this: how comes then that in Europe and North America, they are in the middle of summer – their hot season?

Obviously, the person who came up with that message forgot what they learnt in primary school: that the seasons on earth are caused, not by the planet’s distance from the sun, but by the tilt of its rotational axis with respect to its axis of revolution – the often quoted 23.5 degrees.

If you are wondering what this is all about, here is a quick reminder: the path of the earth on its journey around the sun is not a circle. It is an ellipse – it is longer in one direction than in the other. Looks like an oval, but more symmetrical. For that reason, the distance to the sun does not remain constant throughout the year.

In January, the Earth is about 147 million km from the sun while in June it is 152 million km away. Clearly then, we are now about 5 million km farther from the sun than we were in January. But that cannot be the reason for the cold weather that we are experiencing. If it was the cause, then the northern regions of the world would also be very cold. Yet they are in their hottest month.

In fact, looking at the overall global temperatures, it turns out that, on average, the months of June and July are the hottest while December and January are the coldest. As we all learned in school, the seasons are determined by the tilt of the earth’s axis.

Right now, the Northern part of the globe is tilted towards the sun and so, it is receiving more direct sunshine than the southern region. In addition, if you look at the map of the world, you will notice that there is more dry land in the north than in the south. Consequently, the planet gets hotter in this season than when the direct sunlight is in the south.

When the southern hemisphere is getting direct sun in January, most of the solar radiation falls on water. Water is slow in heating up and so the global average temperature is not as high.as in June and July.