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Pressures from greenhouse gas emissions

Natural causes versus human activities

The Earth’s atmosphere consists mainly of nitrogen and oxygen – non-greenhouse gases that do not interact with infrared radiation. On the other hand, greenhouse gases absorb infrared radiation flowing upwards from Earth’s surface and impede outward flow of infrared energy from Earth to space. These greenhouse gases, when existing in natural concentrations, act to warm the surface of the Earth and provide a habitable temperature.

Human activities have enhanced this greenhouse effect since the beginning of the agricultural and industrial revolutions by directly increasing atmospheric concentrations of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) as well as chemically manufactured greenhouse gases, such as halocarbons.

Humans also indirectly increase the concentrations of water vapour (which accounts for about half the natural greenhouse effect) through increasing global temperature, amplifying the direct warming impacts. Human-induced drivers of climate change have been much larger than natural drivers over the last century, during which changes from solar cycles, variations in the Earth’s orbit and CO2 emitted by volcanoes became negligible when compared with CO2 emissions from human activities.

Some of the warming is masked by the net cooling effects of increased aerosol concentrations. Aerosols are tiny solid or liquid particles suspended in the atmosphere, produced from industrial activity, dust and sea salt. They directly impact radiation by reflecting solar radiation back to space, but they also have indirect impacts through their effect on clouds.


Global greenhouse gas emissions have risen steeply since the beginning of the industrial revolution, with the largest increases coming after 1945. Total global greenhouse gas emissions have roughly doubled since 1970 and have grown dramatically since 2000. Similar to Australia, energy related emissions account for more than 70% of global emissions. In 2017, worldwide energy related emissions were at 32.53 Gt, up from 15.54 gigatonnes (Gt) in 1975, reaching 20 Gt in 1990, and 30 Gt in 2010.

A relatively small number of countries produce the majority of greenhouse gas emissions. The 25 largest emitters produce approximately 78% of global emissions.

Maritime transport emits around 1,000 million tonnes of CO₂ a year and is responsible for about 2.5% of global greenhouse gas emissions. More than 52,000 ships are navigating the world’s ocean trade routes, burning more than 2 billion barrels of heavy fuel oil a year. Emissions from the shipping sector can be expected to continue to expand in concert with the growth in global trade, 90% of which is seaborne. In addition to its contribution to greenhouse gas emissions, the fuel used in ships contains sulfur at concentrations 1,800 times higher than that used in road vehicles, thereby also significantly contributing to air pollution.

See the world's ocean trade routes


Australia’s contribution of greenhouse gas emissions are significant globally. Australia ranked 13th in the world based on total domestic emissions in 2014, as shown in Table 3. Australia, together with other countries whose emissions each contribute less than 2%, make up more than a fifth of global emissions.

Australia’s emissions per capita are the 7th highest in the world, higher than any of the top 25 emitting nations and the highest of the Organisation for Economic Co-operation and Development (OECD) member countries. Compared with other OECD nations, Australia’s reliance on fossil fuels for generating electricity is a key cause of our high per capita, and high per unit of GDP, emissions.

Table 3: Top 25 greenhouse-gas-emitting nations (excluding land use change) in 2014

Rank Country Total GHG emissions excluding LULUCF (MTCO2e) Total GHG emissions including LULUCF (MTCO2e)
  World 45,741 48,892
1 China 11,912 11,601
2 United States 6,371 6,319
3 India 3,080 3,202
4 Russian Federation 2,138 2,030
5 Japan 1,315 1,322
6 Brazil 1,051 1,357
7 Germany 854 817
8 Indonesia 789 2,472
9 Canada 745 867
10 Iran 734 801
11 Mexico 722 729
12 Korea, Rep (South) 671 632
13 Australia 590 523
14 Saudi Arabia 583 583
15 South Africa 525 527
16 United Kingdom 506 494
17 Turkey 431 367
18 France 413 334
19 Italy 403 369
20 Thailand 358 374
21 Poland 353 328
22 Argentina 349 443
23 Ukraine 348 344
24 Pakistan 333 362
25 Malaysia 317 188

Source: World Resources Institute

According to the 2016 Australia State of the Environment Report:

  • The energy sector continues to be the dominant source of Australia’s greenhouse gas (GHG) emissions, accounting for 76% of net emissions in 2015.
  • Australia’s total emissions (including land use, landuse change and forestry LULUCF) have decreased by an average of 1.1% per year since 2006. This compares with an average increase of 0.3% per year from 1990 to 2000.
  • When LULUCF emissions are excluded, total emissions have generally increased.

The LULUCF sector accounted for 2% of Australia’s GHG inventory in 2015 and includes emissions from deforestation, forest management, afforestation and reforestation, grazing land management and crop land management. Emission levels of the sector tend to vary significantly from year to year, reflecting extreme events such as bushfires and drought, which lead to a major loss of carbon from vegetative and soil sinks.

South Australia

South Australia contributed 5% of Australian net emissions in 2016 (Figure 11), at 26.3 million tonnes (Mt) of CO2 equivalents. These included the highly variable net emissions from the LULUCF sector.  

The ‘CO2 equivalent’ (CO2-e) is a measure of how much global warming a given type and amount of greenhouse gas may cause, using the functionally equivalent amount or concentration of CO2 as the reference.

soer2018_national_emissionsFigure 11: Contribution to national emissions by state and territory for 2016.
Source: Australian Government

The energy sector is the dominant source of SA’s emissions, as shown in Figure 12, contributing 64% of the total in 2016. Emissions from the energy sector include emissions from electricity generation, direct combustion of fuels on site (such as gas and diesel to produce stationary energy), combustion of fuel for transport, and net electricity imports over the interconnector.


Figure 12: South Australia’s greenhouse gas emissions 2016

Total energy sector emissions peaked in 2008, declining each year until 2015 as a result of the increase in renewable energy generation, followed by a small (1%) increase in 2016.  

Energy emissions include emissions from transport, which have increased by 22% from 5.4 megatonnes (Mt) in 1990 to 6.6 Mt in 2016, and made up 25% of SA’s emissions in 2016.

South Australian emissions per capita declined by about 30% from 23 to 15.4 tonnes of CO2-e/person between 1990 and 2016 and remain substantially lower than the national average of 21.7 tonnes of CO2-e/person for 2016. Similarly, the greenhouse gas intensity of the SA economy has more than halved since 1990 – that is, the tonnes of CO2-e produced per million dollars of gross state product.

Total annual SA net emissions in 1990 were 32.9 Mt (Table 3) and, after an initial fall in the early 1990s, began to rise in the late 1990s to a peak of 34.2 Mt in 2006. Total emissions then decreased, particularly from 2007, to 10% (or 6.6 Mt) lower than 1990 emissions in 2016 (including LULUCF).

Table 3: South Australia's total annual greenhouse gas emissions


Emissions (Mt of CO2-e)











%change 2005–16











Industrial processes








































Total including net LULUCF