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Water and Carbon Cycles

Rising atmospheric carbon, the energy budget and its impacts

  • 2 things to know
  • Component 2

Overview

Greenhouse effect in terms of the energy budget, radiative forcing and ocean acidification.

What you need to know

Answer each one before you reveal it.

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Key term

State the main causes of the recent increase in the atmospheric carbon store.

Numbers

By how much has atmospheric carbon dioxide risen since pre-industrial times?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    State the main causes of the recent increase in the atmospheric carbon store.

    Model answer

    Fossil fuel combustion for energy, transport and industry is the dominant cause. Deforestation, cement manufacture and agriculture supply the remainder.

  2. 2

    By how much has atmospheric carbon dioxide risen since pre-industrial times?

    Model answer

    Carbon dioxide has risen from about 280 parts per million to around 420 parts per million by 2023. The increase is roughly a half in under three centuries.

  3. 3

    Roughly how much solar radiation reaches the top of the atmosphere?

    Model answer

    Averaged over the whole Earth, roughly 340 watts per square metre arrive at the top of the atmosphere. Around 30 per cent of that is reflected straight back to space.

  4. 4

    Explain the greenhouse effect in terms of the energy budget.

    Model answer

    Greenhouse gases are transparent to incoming shortwave radiation but absorb outgoing longwave radiation. Absorbed energy is re-radiated in all directions, warming the lower atmosphere and surface.

  5. 5

    Define radiative forcing.

    Model answer

    Radiative forcing is the change in the Earth's energy balance caused by a factor such as extra carbon dioxide. Measurement is in watts per square metre.

  6. 6

    Roughly what radiative forcing has extra carbon dioxide produced since 1750?

    Model answer

    Additional carbon dioxide has produced a radiative forcing of roughly 2.2 watts per square metre since 1750. Other greenhouse gases add a further contribution on top.

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Water and Carbon Cycles

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