Identifying the causes of climate change is crucial if we want to slow down the warming of the planet. Temperatures are increasing at rapid levels worldwide, with observable effects on the environment. Glaciers are melting, sea levels are rising and heat waves are intensifying.

Evidence shows that the net damage costs of climate change are likely to be significant and will only increase over time. Among other reasons, this is because temperatures will continue to rise in the decades to come, according to scientists.

What causes climate change?

The concentration of certain gases in the atmosphere prevents heat from escaping. This phenomenon, also known as the greenhouse effect, is why the planet is rapidly warming. Some of the greenhouse gases (GHG) that are significant contributors to this effect are carbon dioxide (CO2), methane and nitrous oxide.

Although these gases can occur naturally, human activity is a key contributor to high concentrations of GHGs in the atmosphere. In fact, there is more than a 95 per cent probability that human activities over the past 50 years have warmed our planet. This is according to the Intergovernmental Panel on Climate Change (IPCC)’s Fifth Assessment Report.

graphic of Greenhouse gas increase up to 2010

IPCC’s Fifth Assessment Report

What are the five primary human causes of climate change?

Producing energy is the human activity with the biggest CO2 footprint. Therefore, energy production is the main cause of climate change driven by humans. Nevertheless, energy generation takes different forms when it comes to CO2 emissions. For this top five, we will divide energy production into three categories: energy use in industry, energy use in buildings and transport.

In 2016, greenhouse gas emissions totalled 49.4 billion tonnes of CO2e. The following are the top five drivers with their contribution share:

> Energy: 73.2 per cent

  • Energy use in industry (e.g. iron and steel; chemical and petrochemical; and food and tobacco): 24.2 per cent
  • Energy use in buildings (both commercial and residential): 17.5 per cent
  • Transport (e.g. road transport, aviation and shipping): 16.2 per cent

> Agriculture, forestry and other land use (AFOLU) (e.g. livestock, crop burning and deforestation): 18.4 per cent

> Industry (e.g. cement and chemicals): 5.2 per cent

While other sectors significantly contribute towards climate change, emissions from energy generation are certainly one of the biggest drivers. This is due to the burning of fossil fuels.

graphic of global greenhouse gas emissions by sector

How does burning fossil fuels increase greenhouse gases, particularly carbon dioxide?

CO2 emissions from fossil fuel burning and industrial processes jointly contributed about 78 per cent of the total GHG emission increase from 1970 to 2010. Despite an increase in global renewable energy usage in recent years, coal, oil and gas are still dominant in the world’s energy mix. This means that transport, electricity production and heating are mostly the result of burning fossil fuels in most places worldwide.

Australia is an example of this. The country is among the nations with the highest fossil fuel consumption per capita. In fact, Australia’s fossil fuel consumption per capita in 2019 was 64,592 kWh. This was far higher than countries like China (23,373 kWh) and India (6,303 kWh).

As a result, emissions caused by burning fossil fuels for energy and cement production are high in Australia. In 2020, Australia’s emissions (15.37 tonnes) were higher per capita CO2 emissions than in the US (14.24 tonnes), China (7.41 tonnes) and India (1.77 tonnes).

That said, other factors also impact climate change.

How are other drivers of climate change producing CO2e emissions?

The global food system, which includes production and post-farm processes like distribution, is also a key contributor to GHG emissions and climate change. For example, deforesting forests and other carbon sinks in order to convert them into cropland or pasture results in carbon dioxide emissions. Indeed, agricultural expansion accounted for 24 per cent of food emissions in 2018. Also, on-farm processes related to animals raised for meat, dairy, eggs and seafood production accounted for 31 per cent of GHGs in the same year.

Similarly, producing cement and chemicals, such as ammonia, generates direct CO2 emissions. Ammonia is a raw material used to produce plastic, fertilisers, pesticides and textiles. As a result, cement production accounted for three per cent of direct industrial process emissions in 2018. Meanwhile, chemicals and petrochemicals were responsible for 2.2 per cent.

How can these drivers be mitigated?

Burning fossil fuels to produce energy is the main cause of climate change. Therefore, we need to decarbonise this sector urgently. In other words, we need to produce clean electricity, in addition to electrifying transport and heating.

Some countries have made more progress than others in this urgent transition. For instance, 59 per cent of per capita electricity in the UK comes from low-carbon sources. In contrast, 75 per cent of per capita electricity in Australia comes from fossil fuels, mainly coal.

Mitigating food emissions is currently more challenging, as no fully viable technological solutions are available yet. Cutting emissions from this sector would require changes to diets, food waste reduction and improvements in agricultural efficiency. Additionally, it is necessary to develop technologies that make low-carbon food options scalable and cheap. But, there is no clear pathway for this yet.

Our priority should be decarbonising the energy sector. Energy production has the highest CO2 footprint, with higher emissions than the global food system and industry. Moreover, fossil fuels are behind these emissions, and we have the available technology to leave fossil fuels behind.

We must slow down the effects of climate change, and countries should accelerate their transition towards clean sources of energy.