Climate trends and projections for SA

Changing climate is affecting South Australia's:

• temperature
• rainfall
• impacts on the ocean
• frequency and intensity of extreme or adverse events.

This information is from the Bureau of Meteorology and CSIRO State of the Climate 2022 report, which uses the latest monitoring, science and projection information to describe variability and changes in Australia’s climate.

Temperature

Average temperatures in South Australia are now nearly 1°C warmer than in 1960.

This warming means that extreme heat events are more common and drought conditions are more severe. Nine of the 10 hottest years on record in South Australia have occurred since 2005.

Rainfall

There has been a sustained decline in rainfall in many of South Australia’s agricultural regions.

Australian rainfall is highly variable and is strongly influenced by phenomena such as El Niño and La Niña. However, the year-to-year variability happens against a long-term background tend of drying across much of the southern half of Australia.

Southern Australia has had below average rainfall from April to October, for 17 of the last 20 years. The long‑term reduction in rainfall has led to even greater reductions in streamflow.

Declines in streamflow have also been observed in the Murray-Darling Basin into the South Australian Gulf, which includes Adelaide.

Climate effects on the ocean

Climate changes continues to pose a significant risk to the South Australian marine systems by multiplying environmental changes on top of natural climate variations and their extremes.

Sea levels

Sea levels along South Australia’s coast continue to rise by 2 to 4 cm per decade. They are expected to rise by up to 16 cm above the 1986 to 2005 mean level by 2030.

The effects of sea level rises will probably be stronger due to increases in the intensity of extreme events, such as wind-generated storm surges.

This means coastal defences will need to be higher in the coming decades so they can offer the same protection that they give today.

Sea surface temperatures

Sea surface temperatures around Australia have been increasing since 1920 by about 0.1˚C per decade (1˚C per century), as oceans continue to absorb heat from the atmosphere.

In South Australia, most of the shelf waters during warmer months (October to April) have increased between 0.2 to 0.4°C each decade.

Like land-based systems, the frequency of marine extreme events has increased over the last decade. For example, marine heatwaves (when water temperatures rise by 2 to 4°C for days or weeks above their typical values).

This increase is associated with changes in the climate drivers, such as the Southern Annular Mode and Indian Ocean Dipole. These influence:

• sea surface temperature
• surface winds
• oceanic current patterns.

Seawater acidity

The absorption of CO₂ by the oceans has been connected to the increase in seawater acidity.

Oceans to the south of Australia are acidifying faster than those to the north. South Australian shelf waters have decreased in pH by approximately 0.11 over the last century.

At a seasonal scale, the lowest acidity waters are observed during periods of strong summertime upwelling. This increasing trend in acidity has been supported by an identified decrease in bottom water temperatures by 0.17°C per year since 2008 in the Kangaroo Island upwelling centre.

These changes in seawater acidity are linked to declines in phytoplankton biomass and primary productivity, coinciding with increases in zooplankton biomass. This indicates a shift in the regional foodweb structure, with unknown implications for fisheries productivity in South Australian waters.

Agricultural greenhouse gas emissions

Greenhouse gas (GHG) emissions from human activity are causing unprecedented global warming. A lot of these gases are from agriculture.

Agricultural GHG emissions are methane (CH₄) and nitrous oxide (N₂O). These gases are considered potent greenhouse gases with a global warming potential far greater than carbon dioxide. Methane has 25 times the global warming potential of CO₂, and N₂O is 298 times that of carbon dioxide.

Agriculture’s emission-generating activities, from highest to lowest emissions nationally, are:

1. enteric fermentation in ruminant livestock (eructation and flatulence)
2. agricultural soils
3. prescribed burning of savannas
4. manure management
5. liming and urea application
6. rice cultivation and field burning of agricultural residues.

Nationally, agriculture accounts for around 15% of Australia’s total GHG emissions. In 2017, South Australia’s agriculture sector was the second biggest emitter of GHG emissions – around 24% of the state’s total. The transport sector was responsible for 30% of the state’s emissions.

The largest agriculture GHG emitter in South Australia is animal enteric fermentation (CH4 emissions) at 56%, with sheep responsible for 54% and beef cattle 35%.

Reduction commitments

In South Australia, and nationally, many agriculture organisations have committed to reducing their emissions. They are actively working on strategies for carbon neutrality or significant reductions. For example, in 2017 Meat and Livestock Australia committed to being carbon neutral by 2030.

Possible ways to reduce carbon emissions in primary industries include:

• carbon storage and capture in soils, vegetation and coastal ecosystems
• low-carbon farming practices
• changes in livestock management
• using renewable energy and biofuels
• feed supplements to reduce methane emissions from ruminant livestock (still in development).

There is also increasing research and investment in areas such as:

• blue carbon
• different pasture species with lower enteric emissions
• selective breeding
• genetic manipulation.