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Ocean Warming and Kettles


Resource produced in conjunction with Sustainability Physics.

Teachers’ Notes


The world’s oceans are heating. Their temperature is not rising as fast as that of the land or air, but they are the major store of the excess thermal energy resulting from greenhouse gas emissions

The top 700m of the oceans have warmed by 0.18°C on average between 1955 and 2010.

This resource investigates how big this store of thermal energy is.

  1. Why does the temperature of the sea rise more slowly than the temperature of the land or air?
  2. Find the area of the Earth’s oceans using the following information: the radius of the Earth is 6400km and the oceans cover about 70% of the Earth.
  3. Find the volume of the top 700m of the oceans. Ignore all the coastal sections of the ocean which are shallower than 700m.
  4. Find the mass of the top 700m of the ocean. Use the density of seawater as ρ = 1025 kg/m3
  5. Find the energy required to give this mass a temperature rise of 0.18°C. The specific heat capacity of sea water is 4 kJ/kg/K
  6. Find the average power over the 55 year heating period
  7. How big is that power? Find the power ‘per person’ by dividing the total power by the number of people on Earth today (8 billion people)
  8. A kettle has a power of 2.5kW. How many kettles would each person on the Earth have to boil to have the same total power?

Start exploring

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