Fossil fuels are formed from decomposed plants and animals that died hundreds of millions of years ago. They are all hydrocarbons – made up of carbon and hydrogen – that resulted in carbon-rich deposits of coal, natural gas and crude oil. Fossil fuels are non-renewable, finite sources that supply around 80 per cent of the world’s energy in the form of electricity, heating and transportation. 

The greenhouse gas (GHG) emissions from mining, processing and burning fossil fuels are the leading driver of the greenhouse effect that is causing global warming and climate change. American scientist Eunice Foot first discovered in 1856 that the GHG carbon dioxide (CO2) absorbs heat and that rising atmospheric CO2 would cause Earth’s temperature to rise. Newspapers have reported on the link between burning coal and the greenhouse effect for over a century. Despite this, nations continue to burn fossil fuels, GHG emissions continue to increase each year, and our planet keeps on heatingOver half of all human-produced CO2 emissions are from the last three decades alone.

The fossil fuels

Coal, natural gas and oil are three commonly used fossil fuels. They have many other names, forms and derivatives. These include diesel, gasoline, kerosene, petroleum, bitumens, heavy oils, liquefied natural gas (LNG), liquefied petroleum gas (LPG) and compressed natural gas (CNG). There are also thousands of everyday products manufactured using chemicals derived from fossil fuels, including clothing (polyester, nylon, acrylic), tyres, pharmaceuticals and plastics.


Coal comes from accumulated plant matter in swamps and peat bogs from millions of years ago. This matter was buried and exposed to high heat and pressure – mainly due to the shifting tectonic plates – and transformed into coal. Coal is found in underground formations known as ‘coal seams’ or ‘coal beds’ that can be 30 metres wide and 1,500 kilometres long. Coal seams exist on every continent — with the largest in the US, Russia, China, India and Australia. Extraction is via surface mining or underground mining. Humans burn coal directly for heat and industrial processes or to fuel power plants to generate electricity.

There are four main types of coal: anthracite, bituminous, subbituminous and lignite. The way we determine the type of coal is by assessing the amount and type of carbon the coal contains, as well as the amount of heat energy it can produce. 

Coal is by far the dirtiest form of energy production. Burning coal releases many toxins and GHGs, causing air pollution, climate change and environmental destruction. Australia has the highest coal power emissions in the world per capita.

Natural gas

Natural gas is formed from millions of years of heat and pressure that caused the carbon bonds of decomposed plants and animals to break down. This created underground reservoirs of thermogenic methane: natural gas. When it exists in permeable material beneath impermeable rock and is easily accessible to extract, it is ‘conventional’ gas. In other geological settings, where it is more difficult and expensive to extract, it is ‘unconventional’. We use natural gas for heating, cooking, electricity generation and fuelling certain vehicles. 

Gas companies drill to extract natural gas, and the extraction process causes land degradation and toxic air, water and soil pollution. Extracting unconventional gas sources also requires highly damaging and controversial techniques, such as fracking. Furthermore, gas infrastructure is prone to methane leakage. Scientists have found that this doubled the climate impact previously thought, causing a warming impact as severe as coal. As of 2022, Australia is the world’s biggest LNG exporter.

Crude oil

Crude oil, or petroleum, is a liquid fossil fuel. It is found at the sites of ancient seas where plants, algae, and plankton were buried and crushed under millions of tons of sediment. Oil exists in vast underground reservoirs beneath land or ocean floor, in the cracks and pores of sedimentary rock, or in tar sands near the Earth’s surface. 

Oil companies extract underground crude oil with giant drilling machines or by strip mining in the case of tar sands oil.  Extraction poses substantial environmental risks. For example, oil spills cause enormous ecological disasters. On land, bitumen extraction from tar sands is also incredibly harmful to the environment as it contains high amounts of sulfur and heavy metals.

Oil is currently the world’s largest energy source. Both petrol and diesel are made from crude oil. We use it for heating and processing into thousands of different items, including tires, refrigerators and even anaesthetics. In 2021, oil contributed around one-third of Australia’s energy

Fossil fuels and greenhouse gas emissions

Burning fossil fuels emits billions of tonnes of GHG emissions into our atmosphere every year. They are carbon dioxide, methane, nitrous oxides and water vapour, as well as ozone and chlorofluorocarbons.

Carbon dioxide

One of the main byproducts of fossil fuel combustion is CO2. The ever-increasing burning of fossil fuels is increasing the concentrations of planet-warming CO2 in our atmosphere and ocean, where it remains for 300 to 1,000 years. Atmospheric carbon dioxide concentrations reached 421 parts per million (PPM) in May 2022, a level not seen for millions of years.


Methane (CH4) is a potent GHG with over 80 times the warming potential of carbon dioxide over its first 20 years in the atmosphere. This potency means methane has contributed around 40 per cent of total global warming to date. Methane concentrations in our atmosphere have doubled since the industrial revolution. 

Nitrous oxide

Fossil fuel combustion is an important source of nitrous oxide (N2O) emissions, which has a warming impact 300 times that of CO2. When burning fossil fuels, part of the nitrogen in the fuel and surrounding air oxidises, creating N20 emissions. N2O emissions have risen 30 per cent over the past four decades.

Water vapour 

Water vapour (H2O) is Earth’s most abundant GHG. It is responsible for about half of Earth’s greenhouse effect as it “amplifies” the warming effect of the other GHGs, according to NASA. Because warmer air holds more moisture, water vapour concentrations increase, absorbing and trapping Earth’s heat and resulting in further warming. This is what scientists call a “positive feedback loop”.

The impact of fossil fuels on the climate, environment and human health

The coal, oil and gas industries cause significant climate, environmental and health costs that are external to market prices. Every stage of the fossil fuel supply chain – from mining, processing, transporting and burning – generates external impacts and costs on our lives and planet. 

Fossil fuels’ impact on the climate

Extreme weather

The climate impact of burning fossil fuels is causing more frequent and severe extreme weather events. Every year, heatwaves, wildfires, hurricanes, wind storms, flooding and droughts cost the world economy USD $520 billion and push 26 million people into poverty. Continuing down this path means vast areas of our planet could become inhabitable over the coming decades due to burning fossil fuels.

Sea level rise

Our warming atmosphere and ocean are melting glaciers and land-based ice sheets, resulting in global sea level rise. This is causing more frequent flooding, destructive storm surges and saltwater intrusion. Millions of people living in coastal zones – including major cities, low-lying islands and coastal communities – are predicted to be impacted this century as seas continue to rise. 

Ecological breakdown and ‘tipping points’

Climate change is pushing Earth’s ecological systems out of balance and risks triggering planetary ‘tipping points‘. These are sudden and dramatic changes that push a system into a new, irreversible state. They include Greenland and West Antarctica ice sheet disintegration, permafrost thaw, Amazon rainforest die-off, coral reef die-off and West African and Indian monsoon shifts. 

Fossil fuels’ impact on the environment

Air and water pollution

The fossil fuel industry produces hazardous air pollutants, including sulfur dioxide, nitrogen oxides, particulate matter (PM2.5), carbon monoxide and mercury. These can cause acid rain and eutrophication, damage crops and forests and harm wildlife. Toxins from coal mining can also leach into groundwater, and oil spills can devastate marine life. Fracking for gas creates wastewater containing substances such as arsenic, lead, chlorine and mercury that can contaminate ground and drinking water.

Ecosystems and species

Mining fossil fuels caused widespread destruction to landscapes and ecosystems. For example, surface coal mining and mountaintop removal mining obliterate landscapes, destroying habitats and entire ecosystems. It can also put areas at greater risk of landslides, erosion, floods and other natural hazards. Oil drilling in areas such as the Amazon and the Democratic Republic of Congo is associated with ecological destruction and human rights abuses. Furthermore, extreme heat, wildfires and drought caused by global warming are devastating wildlife populations and threaten extinctions. 

Ocean acidification

The ocean absorbs atmospheric CO2, which changes the water’s pH, making it more acidic. This increased acidity dissolves the shells of marine organisms and makes it harder to build shells and coral skeletons. Over the last 150 years, ocean acidity has increased by 30 per cent, threatening coral reefs and marine ecosystems.

Fossil fuels’ impact on health

Toxic air pollution

Globally, burning fossil fuels was responsible for 8.7 million deaths in 2018, equivalent to one in every five deaths. This is primarily through toxic air pollution, including PM2.5, which absorbs deep into the blood and organs. This causes serious health problems, such as cardiovascular disease, cancer, tissue damage and asthma. Fossil fuels also emit toxic chemicals including lead, arsenic and mercury. These can seriously damage peoples’ brains and mental abilities, leading to dementia and possibly Alzheimer’s disease.

Unequal impacts

Toxic air pollution is especially dangerous for young children, whose organs and immune responses are still developing, and they breathe in more air pollution relative to their body weight. Older adults are also at high risk of air pollution impacts on dementia and Alzheimers. Air pollution also disproportionately affects poorer and deprived communities, leading to increased global health inequalities. 

Additional hazards for fossil fuel workers

Workers in the fossil fuel industry can suffer from exposure to its high health risks. For example, coal mining is one of the most dangerous jobs in the world. Coal dust can build up in the lungs, causing “black lung” respiratory illnesses. In addition to disease, mine explosions, collapses and other accidents kill thousands of coal miners annually.

The fossil fuel industry

The world consumes almost 15 billion tonnes of fossil fuels every year. Fossil fuels are also a significant export commodity. In 2018, countries traded more than four billion tonnes of these fossil fuels around the world, making up 40 per cent of all shipping trade by weight.

Globally, the oil and gas industry alone has profited an average of USD $1 trillion every year since 1970. Despite this, oil and gas companies often pay little in tax. A 2022 report found that five Australian fossil fuel giants have paid no tax on a combined income of AUD $138 billion from their Australian operational profits over the past seven years. Moreover, governments spend billions of public money heavily subsidising the fossil fuel industry. In Australia alone, the government handed AUD $11.6 billion to the fossil fuel industry in 2021-22, an increase of AUD $1.3 billion from the previous year.

But, while fossil fuels companies are making vast profits, the total global environmental cost of extractive industries – including fossil fuels – comes to USD $5 trillion every year. This is mainly due to the impacts of GHG emissions, particulate matter and acidification — particularly from the coal and steel sectors.

Due to the devastating effects of fossil fuels on people and their environment – in addition to mounting evidence that companies spent decades hiding the impactsclimate litigation cases against these companies are rising globally.

The difference between fossil fuels and renewable fuels

Unlike fossil fuels, renewable energy sources, such as solar, wind and hydropower, are inexhaustible resources that emit no GHGs or air pollution at the point of use. These renewable energies – along with storage – can replace fossil fuels and be transformed into electricity or green hydrogen power for our electricity, heating and transportation needs.

These differ from bioenergy fuels. These are also in the renewable energy category, using biomass to produce biofuels and biogas. However, we still burn them to produce energy, and biomass combustion can still emit GHGs and air pollutants that are harmful to humans and the environment. They can also have a vast ecological footprint. For example, both charcoal and wood chip are widely used biomass fuels but are also significant drivers of deforestation of precious tropical and hardwood forests. Biomass fuels made from crops also increase food prices and drive world hunger. 

This means that the non-combustible renewable energies produced from solar, wind and hydropower are the cleanest and safest options to power our economies in the future.

Replacing fossil fuels with clean, renewable energy

Continuing to burn fossil fuels will make much of our planet uninhabitable. As per the Paris Agreement, the world must urgently scale down our reliance on fossil fuels and transition to renewable energies to avoid the very worst impacts in the future. The ingenuity of scientific and technological breakthroughs in clean energy means that transitioning to 100 per cent emissions-free energy is possible with the solutions we already have. What’s more, renewable systems are more efficient, more affordable and would bring profound benefits to human and ecological health compared to burning the dirty fossil fuels of the past.