The Albedo Effect

Introduction

Earth’s climate heavily depends on solar power. As time goes on, various surfaces — such as land and oceans — absorbs an average of approximately 240 watts of solar power per square meter. This sunlight is the fuel for photosynthesis, evaporation, melting of snow and ice, and warms Earth itself.

The Earth is not heated uniformly by the Sun. The Sun heats equatorial regions more than polar parts because the Earth is spherical. Through the evaporation of surface water, convection, precipitation, winds, and ocean circulation, the atmosphere and ocean continuously attempt to balance out solar heating imbalances. This coupled atmosphere and ocean circulation is known as Earth’s heat engine.

What is Albedo?

It is referred to as the fraction of the sun’s energy reflected back into space. Different aspects of Earth — such as snow, ice, ocean, and clouds — have different albedos. Land and oceans have low albedos, absorbing more solar radiation than they reflect. On the other hand, snow, ice, and clouds have high albedos (typically 70–90%) and reflect more energy than they absorb. Earth’s typical albedo is roughly 30%, meaning around 30% of incoming solar radiation is reflected back into space while 70% of it is absorbed.

This concept aids in our comprehension of the amount of energy that Earth receives from the Sun and the energy that Earth radiates back into space. Earth may be going through a net cooling or warming, depending on the balance. Over the past century, there has been a net warming, which has caused Earth’s temperature to increase by about 0.8°C/0.14°F.

Snow and ice cover less of the Earth’s surface as a result of melting from an increase in global temperature — lowering Earth’s albedo in the process. More energy is absorbed due to the decrease in albedo, which leads to increased warmth and melting. The positive feedback loop between ice and albedo speeds up the rise in global temperature.

Human Contribution

Human activities linked to causing pollution disturbs the energy balance. The burning of coal, oil, and other fuels leads to the development of the carbon by-product: soot. This gets released into the atmosphere and distributes itself on Earth. When it lands on snow and ice, it interferes with the snow and ice’s natural ability to reflect radiation. This is due to darkened snow and ice absorbing more radiation than pure snow and ice. This concept is similar to wearing a black shirt on a sunny day as opposed to a white shirt — you will feel warmer with the black shirt as it absorbs the Sun’s energy instead of reflecting it as the white shirt would’ve. Additionally, as the snow and ice melt, the soot trapped in the snow is left behind and concentrates more on the surface, causing the warming to proceed even faster.