• Amalia Heide


Have you ever thought about why the global temperature is rising? Are you aware of the importance of the Albedo Number to answer this question? How is it that the Albedo number is related to greenhouse gases? All the answers to questions that must be responded are in this article.

The Sun emits heat in the form of radiation. This heat reaches the Earth in the form of waves. Different surfaces on Earth absorb some of this radiation and reflect the rest. The percentage of radiation reflected by any surface is known as the Albedo number. It is measured on a scale from zero (corresponding to a black body absorbing all incident radiation) to one (corresponding to a white body reflecting all incident radiation).

The average albedo of the Earth is 37-39% of the radiation coming from the Sun. This means that 37-39% of the Sun's energy is returned to the universe. A high albedo cools the planet, because the light (radiation) absorbed and used to heat it is minimal. Conversely, a low albedo warms the planet, because most of the light is absorbed by the planet. Therefore, albedo variation can lead to two main effects: cooling (when light is reflected back to space), and warming (when light is absorbed by the Earth).

The amount of absorbed and reflected radiation varies according to the surface. In fact, lighter surfaces absorb less radiation than darker surfaces. This explains why in summer we often wear light-coloured clothes to protect us from the heat, so that the clothes do not absorb the sun's heat but reflect it, thus keeping us cool.

This means that the Earth's albedo is very high on icy or snowy surfaces, as well as in deserts, while it is low in oceans and forests, because of their darker shades. And while this may seem like a small rate, any change in this amount can significantly alter the temperature of the Earth's surface. Recent research has shown that changes in the colour tone of soils can lead to significant changes in the temperature of the affected areas. For example, the melting of a glacier or the melting of significant snow cover in polar areas can contribute to a large-scale increase in global temperature.

This can lead to a vicious circle, since the lower the albedo number, the more radiation is absorbed, the warmer the average temperature of the Earth and, logically, the more glaciers melt. In turn, the more glaciers melt, the lower the Albedo number and the more the temperature rises.

On the other hand, greenhouse gases, such as CO2 and other gases and particulate emissions, are considered to have a significant impact on global warming, partly because they prevent solar radiation reaching the Earth's surface from being reflected back into space and retain it in the atmosphere (i.e. they contribute to the decrease in the Albedo number). The direct consequence is an accelerated and exponential warming of the planet's temperature.

In conclusion, the Albedo number allows us to explain in a synthetic and simple way the causes of global warming and the climate crisis that the whole world is going through. In order to mitigate the impact of this pressing issue, it is necessary to keep the Earth’s Albedo number between 37 and 39% before the vicious circle becomes unstoppable. Greenhouse gases must stop being sent to the atmosphere and this requires international cooperation.

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