Greenhouse Effect (III) - Albedo

The greenhouse effect is a natural process that warms the Earth, helping to maintain constant temperatures which sustains life on Earth. When the Sun’s energy reaches the Earth’s surface, some of it is reflected back to space and the rest is absorbed and re-emitted as heat. The ability of a surface to reflect solar energy is known as its albedo.

Albedo is a measure of the reflectivity of a surface. Simply, when you wear dark coloured clothing in the sun you are much warmer than when you wear light coloured clothing because light colours reflect the solar energy whereas dark colours will absorb it.

Reflectivity of surfaces with high albedo versus low albedo (https://climate.ncsu.edu/edu/Albedo).

Warming air temperatures

Surfaces with high albedo reflect up to 80% of the incoming solar energy. In contrast, surfaces with low albedo will only reflect 10% of the incoming solar energy, absorbing up to 90%. This is emitted as heat into the surrounds, increasing the air temperature.

Arctic environments with lots of snow and ice have high albedo because they reflect a greater percentage of the incoming solar energy. Examples of environments with low albedo, due to their dark colour, are deep oceans and dense forests, which absorb the incoming solar energy.

The reflection of solar energy from sea ice compared to dark coloured oceans (https://www.pmel.noaa.gov/arctic-zone/essay_serreze.html) 

Albedo and the enhanced greenhouse effect

Gain a greater understanding of the greenhouse effect by viewing the AusEarthEd video Greenhouse Effect I: Basics. Human activity such as landscape change and burning of fossil fuels are contributing to the enhanced greenhouse effect by increasing the amount of carbon dioxide in the atmosphere. This is explored in the AusEarthEd video Greenhouse Effect II: Enhanced Greenhouse Effect.

As the temperature of the atmosphere increases, we experience glacial retreat and the break-up of sea ice, increasing the area of deep oceans. Deep oceans are dark coloured and have low albedo, absorbing much of the incoming solar energy. They release this energy as heat, accelerating the melting of sea ice. This increases the area of oceans compared to the area of sea ice, further reducing the local surface albedo.

Modelling albedo and the greenhouse effect

You can investigate the effect of albedo on air temperatures by constructing a simple model of a greenhouse and lining your model with either black or white paper. The AusEarthEd video on the Greenhouse Effect III: Albedo demonstrates one method to model this.

Can you relate your findings to the surface albedo effects in the environment?

Where to now?

• Research further information about the greenhouse effect and investigate more activities at WASP.
• Find out more about the science behind climate at NOAA Climate.gov.
• Explore our local Australian climate through the Bureau ofMeteorology
• Take action on climate change. Some ideas to get you started are in this AusEarthEd video Climate Change: Take Action.