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First teaching 2015

Last exams 2025

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Pathways of Energy Entering the Atmosphere (DP IB Environmental Systems & Societies (ESS)) : Revision Note

Alistair Marjot

Written by: Alistair Marjot

Reviewed by: Bridgette Barrett

Updated on

Pathways of Energy Entering the Atmosphere

  • When solar radiation (insolation) enters the Earth’s atmosphere, some of the energy becomes unavailable for ecosystems due to being:

    • Absorbed by inorganic matter

    • Reflected back into the atmosphere

  • This means very little of the sunlight available from the Sun is converted into biomass in ecosystems

    • About 51% of the available energy from the Sun never reaches producers

  • The pathway of radiation through the atmosphere involves a loss of radiation through reflection and absorption, with the following (approximate) percentage losses:

    • Reflection from clouds ~ 19%

    • Absorption of energy by clouds ~ 3%

    • Reflection by scatter from aerosols and atmospheric particles ~ 3%

    • Absorption by molecules and dust in the atmosphere ~ 17%

    • Reflection from the surface of the Earth ~ 9%

      • The ability of clouds and reflective surfaces on Earth (such as snow and ice) to reflect solar radiation is known as albedo 

  • Of the 49% of solar radiation absorbed by the ground, only a small proportion ends up in producers

    • Most incoming solar radiation fails to enter chloroplasts in leaves because it is reflected, transmitted (passes straight through the leaf), or is the wrong wavelength to be absorbed

    • Of the radiation captured by leaves, only a small percentage ends up as biomass in growth compounds because the conversion of light to chemical energy is inefficient

    • In total, only around 0.06% of all solar radiation falling on Earth is captured by plants

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From the sun to producers - the pathway of solar energy entering the atmosphere

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Alistair Marjot

Author: Alistair Marjot

Expertise: Biology & Environmental Systems and Societies Content Creator

Alistair graduated from Oxford University with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems & Societies. Alistair has continued to pursue his interests in ecology and environmental science, recently gaining an MSc in Wildlife Biology & Conservation with Edinburgh Napier University.

Bridgette Barrett

Reviewer: Bridgette Barrett

Expertise: Geography Lead

After graduating with a degree in Geography, Bridgette completed a PGCE over 25 years ago. She later gained an MA Learning, Technology and Education from the University of Nottingham focussing on online learning. At a time when the study of geography has never been more important, Bridgette is passionate about creating content which supports students in achieving their potential in geography and builds their confidence.

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