Australia, both as an ancient island continent and a society predicated on a federation of states in a representative democracy, entered 2025 with the following two hundred & fifty-eight year climatic background which every single person needs to seriously consider as they navigate this federal election year and what remains of this decade.
Because the decisions made now will affect if or how our own communities, friendship groups and families will cope — because the Australian and global overarching climate and seasonal weather patterns that we grew & prospered under down the generations are quickly disappearing never to return for millennia.
State of the Climate 2024: Report at a glance, excerpts:
Key points
Australia
> Australia's climate has warmed since national records began in 1910.
> The oceans surrounding Australia have also warmed. Chart of the temperature anomaly relative to the 1961 to 1990 average, in degrees Celsius, from 1910 to 2023, for temperatures over Australia and for sea surface temperatures in the Australian region.
> Australia’s climate has warmed by an average of 1.51 ±0.23 °C since national records began in 1910.
> Sea surface temperatures have increased by an average of 1.08 °C since 1900.
> The warming has led to an increase in the frequency of extreme heat events over land and in the oceans.
> In the south-west of Australia there has been a decrease of around 16% in April to October rainfall since 1970. Across the same region, May to July rainfall has seen the largest reduction, by around 20% since 1970.
> In the south-east of Australia, there has been a decrease of around 9% in April to October rainfall since 1994.
> Heavy short-term rainfall events are becoming more intense.
> There has been a decrease in streamflow at most gauges across Australia since 1970.
> There has been an increase in rainfall and streamflow across parts of northern Australia since the 1970s.
> There has been an increase in extreme fire weather, and a longer fire season, across large parts of the country since the 1950s.
> There has been a decrease in the number of tropical cyclones observed in the Australian region since at least 1982.
> Snow depth, snow cover and number of snow days have decreased in alpine regions since the late 1950s.
> Oceans around Australia are becoming more acidic, with changes happening faster in recent decades.
> Sea levels are rising around Australia, including more frequent extreme high levels that increase the risk of inundation and damage to coastal infrastructure and communities.
Anomalies (departures from the mean for the 1961–1990 standard averaging period) in annual mean sea surface temperature, and temperature over land, in the Australian region. Sea surface temperature values (data source: ERSST v5, psl.noaa.gov) are provided for a region around Australia (4–46°S and 94–174°E).
Global
> Concentrations of all major long-lived greenhouse gases in the atmosphere continue to increase. Global annual mean carbon dioxide (CO2) concentrations reached 419.2 parts per million (ppm) in 2023 and the CO2 equivalent (CO2-e) of all greenhouse gases reached 524 ppm. These are the highest levels on Earth in at least 2 million years.
> Global fossil fuel CO2 emissions, the principal driver of the growth in CO2 concentrations, are continuing to increase. Overall anthropogenic CO2 emissions, including fossil fuel and land-use change emissions, have levelled off over the last decade after increasing for more than a century prior to the 2010s.
> In 2022 and 2023, the amounts of methane (CH4) and nitrous oxide (N2O), both greenhouse gases, in the atmosphere increased rapidly.
> Globally averaged air temperature at the Earth’s surface has warmed by about 1.2 °C since reliable records began in 1850. Each decade since 1980 has been warmer than the last, with 2011–2020 being around 0.2 °C warmer than 2001–2010. 2023 was the warmest year on record globally.
> The world’s oceans, especially in the Southern Hemisphere, have taken up more than 90% of the extra energy stored by the planet (as heat) arising from enhanced greenhouse gas concentrations.
> The ice sheets and ice shelves of Antarctica and Greenland are losing ice due to a warmer climate, and contributing to global sea level rise.
> There has been an abrupt decrease in Antarctic sea-ice extent since 2015, after a small increase over the period from 1979 to 2014.
> Around half of all CO2 emissions from human activities are absorbed by land and ocean sinks, which act to slow the rate of increase in atmospheric CO2.
> Global mean sea levels have risen by over 22 cm since 1900; half of this has occurred since 1970.
Future
In the coming decades, Australia will experience ongoing changes to its weather and climate. The changes are projected to include:
> Continued increase in air temperatures, with more heat extremes and fewer cold extremes.
> Continued decrease, on average, in cool season rainfall across many regions of southern and eastern Australia, which will likely lead to more time in drought.
> More intense short-duration heavy rainfall events even in regions where the average rainfall decreases or stays the same.
> Continued increase in the number of dangerous fire weather days and a longer fire season for much of southern and eastern Australia.
> Further sea level rise and continued warming and acidification of the oceans around Australia.
> Increased and longer-lasting marine heatwaves that will affect marine environments such as kelp forests and increase the likelihood of more frequent and severe bleaching events in coral reefs around Australia, including the Great Barrier Reef and Ningaloo Reef.
> Fewer tropical cyclones, but with higher intensity on average, and greater impacts when they occur through higher rain rates and higher sea level.
> Reduced average snow depth in alpine regions, but with variations from year to year.
Changes in weather systems and climate influences
Australia’s weather systems are changing. Southern Australia receives much of its rainfall during the cooler months of the year from low-pressure systems and cold fronts to the south of the subtropical high-pressure ridge. During recent decades, these systems have become less common over southern Australia, and are less likely to produce rainfall when they do occur, contributing to declines in cool season rainfall. Mean sea level atmospheric pressure is increasing over Australia, and there has been an increase in the number of high-pressure systems over southern Australia, which bring dry, clear weather and little rainfall. This increase in atmospheric pressure across southern latitudes is a response to climate change.
There is large variability in the frequency of individual weather systems between individual months and years. Many of these trends are consistent with simulations from climate models, which demonstrate that increased greenhouse gas levels lead to fewer low-pressure systems in southern Australia and a stronger subtropical ridge, but an increase in the intensity of heavy rainfall, including from thunderstorms.
Australia’s climate is also influenced from year to year by various broadscale climate influences, such as the El Niño–Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and the Southern Annular Mode (SAM). SAM shows a sustained trend towards more positive conditions from 1950 to the present day, particularly in summer.
The level of ENSO activity over the past 50 years is higher, with more significant El Niño and La Niña events than in the years between 1920 and 1970. However, there is no clear indication that recent activity levels are outside the long-term range of variability, with evidence of high levels of ENSO activity in the late 19th and early 20th centuries. There is low confidence in the long-term trends in the IOD, particularly prior to the 1960s, although paleoclimate data indicate that the recent frequency of strong positive IOD events is high in the context of multi-century variability.
The full report can be read & downloaded as a pdf at
http://www.bom.gov.au/state-of-the-climate/
