A common misconception is that the regions near or at the equator are hotter because they are closer to the Sun than other zones on the Earth. However, the distance that separates the equator from the poles is so small in comparison to the enormous distance that separates the Earth from the Sun (150 000 000 kilometres), that we can affirm that the Sun shines as intensely at the poles as on the equator.
If there isn’t any difference in the brightness of the Sun at all the points of the Earth, why is the equator hotter than the areas near to the poles? Below, we explain the different reasons that cause the temperature differences on the Earth.
A concentration of solar light
As the Earth is a sphere, the solar rays do not impact all the zones of the Earth at the same angle or with the same concentration:
- At the equator, a fixed quantity of solar rays impacts against the surface directly, without almost any inclination. This provokes that the sunlight arrives at the equator in a more concentrated way: solar rays liberate their energy in a small zone of the rays.
- However, in the regions near the poles, the solar rays that get to the surface do so at a certain angle, and the light concentration is consequently lower. So, the same quantity of light that at the equator covers a small zone, at the poles it covers a much bigger surface.
Therefore, as the equator receives more concentrated energy, the temperatures are more elevated in this zone. However, the low concentration of solar light at the poles is traduced in low temperatures in the regions.
The reflectivity of the Earth’s surface
When the sunlight that arrives on the Earth, part of it is reflected back into the atmosphere and doesn’t get to warm the zone. The quantity of solar rays that are reflected mainly depends on the nature of the surface. The areas that are covered by snow or ice reflect up to 95% of the incident rays. The regions near the equator, however, absorb a great part of the sunlight, which provokes warmer conditions. On the contrary, the polar regions (such as the Arctic of the Antarctic) reflect most part of the solar rays due to the enormous icy surfaces.
As we see, the temperature between the different regions of the Earth varies for different reasons, such as the concentration of sunlight, and the reflectivity of the Earth’s surface. Moreover, other factors such as the atmospheric density can also influence in the temperature.