## Earth’s heat content

## The earth is heating rapidly

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.

## Car trips from Melbourne to Brisbane

It’s 1.3 millio

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