Earth’s heat content

A graph of the Earth’s heat accumulation

The Earth is heating rapidly. In a year, the planet gains 74 times as much energy as the US uses in a year. It is heating by 4 Hiroshima bombs of heat each second. This page details how you get these numbers.

The graph shows the accumulation of heat by the Earth between 1962 and 2008

  • The light-blue shows the heat accumulating in the oceans. The oceans have absorbed over 90% of the heat.
  • The brown shows the heat accumulating in the land, atmosphere and ice.
  • The slope of the dark-blue line shows the rate of the heating.

Graph from Sceptical Science: 27 March 2014
Four Hiroshima bombs worth of heat per second

Scientists use a range of measurements including data from satellites, and robotic floats, to estimate the heat content of the oceans.


The rate of heat accumulation

Let’s consider how fast the Earth is gaining this heat. We need to use large numbers for this, so to be clear:

  • Ten raised to the power of two = 10 x 10 = 10^2 = 100
  • Ten raised to the power of 21 = 10^21 = A one followed by 21 zeros.

The Earth is getting hotter at a rate of:

  • 7,800,000,000,000,000,000,000 joule/year
  • 7.8 x 10^21 joule / year
  • 7.8 multiplied by ten raised to the power of 21 joule per year
  • 2.5 x 10^14 joule/second
  • 2.16 x 10^19 joule/day

It’s 74 times the US energy consumption

The US Energy Information Administration (EIA: Energy Facts) says that in 2018 the US energy usage, including petrol, natural gas, coal, nuclear and renewables, was:

  • 101.3 quadrillion British Thermal Units (Btu)
  • 101.3 x 10^15 Btu (1 Btu = 1055.056 joule)
  • 1.069 x 10^20 joule / year

So, the Earth is heating 73.8 times faster than the US is consuming energy.


It’s 4 Hiroshima bombs per second

The energy released by the atomic bomb dropped on Hiroshima was 6.3 x 10^13 joule. So the Earth is accumulating heat at a rate of 4 Hiroshima bomb detonations worth of energy every second.


It’s 1.3 million-million car trips from Melbourne to Brisbane a year

In terms of the energy in the petrol needed to travel by car from Melbourne to Brisbane.

  • The trip is 1,675 km.
  • Say the car uses 11 litres of petrol per 100 kilometres
  • This gives 184.25 litres of petrol per trip
  • Say the petrol has 32.6 million-joule / litre
  • This gives is 6,007 million-joule / trip
  • The earth is heating by the energy required for 1.3 million-million of these trips per year