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Fossil fuel sources
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Fossil fuel sources

Fossil fuels

It is only since the start of the industrial revolution (ca 1750) that there has been ever increasing use of fossil fuels as these are more concentrated that renewable energy sources. Fossil fuels such as oil, gas and coal are characterised as non-renewable because they were created over very long time periods compared with our current rate of use. In creating useful energy from the combustion of these fuels, a colourless gas called carbon dioxide is created which, being lighter than air, rises and congregates in the upper atmosphere.

Carbon dioxide is one of the six greenhouse gases whose characteristic is that they are able to absorb the heat radiated from the earth’s surface so creating global warming. The world has become very dependent upon fossil fuels as they are easy to extract, transport and utilise and are not dependent upon sunlight, directly or indirectly. However, our increasing use of energy and growing population worldwide has created another global concern which is the finite size of these resources.

Peak oil and gas

All the major models of oil production predict that the world’s oil supply will peak by 2025 and some models predict that the supply has already peaked (Figure 1).

Figure 1: Oil and gas profiles (Source Colin Campbell)

So we will need to reduce our use of fossil fuels not only to limit impacts of climate change, but also to conserve resources for succeeding generations.

Switching from oil to gas is only a short term option as the world’s supply of gas is likely to peak within 10 -20 years. What is of greater concern is not when the oil or gas peaks, but also how the world will manage with ever decreasing amounts of liquid or gaseous hydrocarbons which post peak are likely to lie between 2 and 7% per year.

Even at its lowest rate of decline, the mismatch between demand and supply will be such that it is important to start now to switch from oil and gas to others sources preferably as soon as possible. Such a change will also help to limit climate change.

Leaving in the ground 

The climate change agreement reached in Paris in December 2015 was to prevent the average global temperature exceeding 1.5 C. To avoid irreversible changes in climate will require leaving most of the existing fossil fuels in the ground in order to limit the amount of greenhouse gases congregating in the upper atmosphere.

Modelling shows that this temperature rise sets an upper limit to the amount of global carbon that can be consumed which is estimated to be 885 gigatonnes of carbon. As 565 gigatonnes have already been burnt this leaves only 320 gigatonnes still to be consumed.

The scientists on the Intergovernmental Panel on Climate Change have explained that the longer the world delays with stabilising its carbon emissions, the more severe will need to be the subsequent annual decline to stay within the required average global temperature limit. In 2015 they suggested a scenario which was for the world’s carbon emissions to peak by 2020 and then decrease by 3% each and every year up to the end of this century .

Limit in annual global carbon emissions peak in 2020 and then decline at a rate of 3.2% per annum to limit carbon in atmosphere to 886 gigatonnes by 2100 (IPCC 5 assessment report)

With the ever continuing increase in global emissions, it is now agreed that carbon emissions must reduce to zero by 2050 to avoid irreversible changes in climate. As the world’s carbon emissions have yet to peak in 2020, to achieve zero carbon by 2050 will require an even higher year on year decrease in carbon emissions around 7%.

The only way to meet our current and future energy needs will therefore be to change from using fossil fuels to renewable energies whose usage does not result in the formation of greenhouse gases.

KITH # Activity Age range
1.2   Use of fossil fuels   
  Science, geography
 11 – 18  


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