What is the Albedo?

A scientific term which has become more present and important in the last years when talking about the Arctic is ‘Albedo’. But what does it mean? You know how your parents tell you to wear white T-shirts when it is sunny outside because with a black T-shirt you feel way too hot!? That’s actually what is behind word Albedo.
Albedo has its origin in the Latin language meaning ‘whiteness’ because it explains the level of light reflection of a surface. It is always expressed as a number between 0 and 1. 0 stands for 0% reflection and 1 for 100% reflection. So, surfaces which reflect less sunlight for example will have a smaller number whereas surfaces which reflect a lot light will have a higher Albedo value. It means that dark surfaces as dark blue ocean water or your black T-shirt absorb that sunlight – they keep the light and warmth. That is also an explanation for why it would get too hot in that black T-shirt on a sunny day. However, bright surfaces like snow, ice, white clouds and also the white T-shirt have a higher Albedo number because they reflect the light. It means that the sunlight which is coming down to earth is again going back into the atmosphere – it is being reflected. The picture at the bottom shows how the Albedo effect works. You can already start wondering what that means for the Arctic. Which impact the Albedo effect has on the global climate you will learn here tomorrow!