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/
.png)
