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The Earth's albedo describes the percentage of sunlight reflected back to space, making it a critical element of the planet's energy balance

Summary​

Earth's albedo measures the percentage of sunlight reflected back to space, crucial for maintaining the planet's energy balance. Natural surfaces vary significantly in reflectivity: snow (60% – 89%), ocean ice (50% – 70%), and oceans (6%). Clouds contribute substantially, with reflectivity varying from under 10% to over 90% based on type and conditions. Human-made surfaces like asphalt (10%) and white buildings (60%) also impact albedo. Atmospheric particles and aerosols further influence reflection. Changes in albedo from ice loss, urbanization, or land management directly affect climate by altering absorbed solar radiation levels. The potential loss of Antarctic ice represents a critical climate tipping point for the earths albedo due to its significant role in Earth's reflectivity.

The Earth's albedo (reflectivity) refers to the measure of how much sunlight (solar radiation) is reflected by a surface back into space, without being absorbed. It is expressed as a fraction or percentage, where a higher albedo means more sunlight is reflected, and a lower albedo means more sunlight is absorbed. On Earth, albedo plays a crucial role in the planet's energy balance, which affects global temperatures and climate. Albedo (or reflective coefficient) is measured as a percentage where 0% means that all sunlight is absorbed and 100% means that all sunlight is reflected. The average albedo of Earth is estimated to be around 30% 1.

The natural surfaces on Earth all have their own unique albedo with some common approximate values being 2:

Surface (natural)Albedo Range
Snow60% – 89%
Ocean ice50% – 70%
Ocean6%
Deciduous forest15% – 18%
Soil17%
Green grass25%
Desert sand40%

Clouds are also one of the main sources of albedo on Earth and can range between below 10% and more than 90% depending on the type of cloud, altitude, moisture content, and the angle at which sunlight hits the cloud 3.

Human-made objects also have their own albedo with some estimated values being 4:

Surface (human-made)Albedo
Asphalt10%
Concrete22%
Dirt roads4%
Gravel20%
White-colored buildings60%

Similarly to clouds, albedo is also influenced by particles in the atmosphere such as aerosols, which can absorb and scatter sunlight, reflecting a portion of it back into space. Climate change and albedo are directly related as reductions to Earth's albedo directly affect the amount of solar radiation that is absorbed by the planet. Actions such as deforestation and urbanization can lead to a reduction in albedo, while reforestation and other land management practices can increase it. One of the biggest concerns relating to future climate change is the known tipping point of loss of Antarctic ice, which is a large contributor to the Earth's albedo, and would be catastrophic for life on Earth.

Sources​

Footnotes​

  1. Wild, M., Folini, D., Schär, C., et al. (2013). The global energy balance from a surface perspective. Climate Dynamics, 40(11-12), 3107–3134. https://doi.org/10.1007/s00382-012-1569-8 ↩

  2. Haynes, W. M. (Ed.). (2014). CRC handbook of chemistry and physics (95th ed.). CRC Press. ↩

  3. Hartmann, D. L. (2016). Global physical climatology (2nd ed.). Elsevier. ↩

  4. Piragnolo, M., Masiero, A., Fissore, F., & Pirotti, F. (2015). Solar irradiance modelling with NASA WW GIS environment. ISPRS International Journal of Geo-Information, 4(2), 711–724. https://doi.org/10.3390/ijgi4020711 [50m]: # ↩