Climate change is having a significant impact on the ACT, with clear evidence of a warming climate and increased occurrence of heat days. Rainfall is variable, but most recent years have been drier than average. Projections suggest a worsening climate with hotter temperatures and decreased rainfall.
Indicator assessment legend
Environmental condition is healthy across the ACT, OR pressure likely to have negligible impact on environmental condition/human health.
Environmental condition is neither positive or negative and may be variable across the ACT, OR pressure likely to have limited impact on environmental condition/human health.
Environmental condition is under significant stress, OR pressure likely to have significant impact on environmental condition/ human health.
Data is insufficient to make an assessment of status and trends.
Adequate high-quality evidence and high level of consensus
Limited evidence or limited consensus
Evidence and consensus too low to make an assessment
Assessments of status, trends and data quality are not appropriate for the indicator
The data presented in this indicator shows the impact of climate change on temperature and rainfall the ACT region. Projected climate trends are also discussed.
The ACT’s climate is determined by atmospheric conditions and sea-surface temperatures. The main drivers of natural climate variability include (but are not limited to) the El Niño–Southern Oscillation (including La Niña cycles), the Indian Ocean Dipole, and the Southern Annular Mode which influence climate across south-eastern Australia. Changes in the frequency and duration of these drivers cause year-to-year variations in temperature and rainfall.
This natural climate variability is now significantly influenced by human-induced climate change. Evidence of global and regional warming caused by greenhouse gas emissions is incontrovertible.
Condition and trends
Observed surface temperature
The ACT’s annual mean maximum temperatures have risen by over 1.5°C since records began in 1926 (Figure CC1). The frequency and severity of hot temperatures have also increased (see Figure CC2). Since 2013, every year has been among the eleven warmest years on record for daytime temperatures and 2018 was the warmest year on record for daytime temperatures in the ACT.
Figure CC1: ACT mean maximum temperature anomaly (as calculated from the 1961 to 1990 average), 1926 to 2018.
In the ACT, minimum temperatures have warmed the most, with annual mean minimum temperatures having risen by around 2°C since records began in 1926 (Figure CC2). Recent warm years include 2016 which was the warmest year on record for mean minimum temperatures and 2018 which was the tenth warmest year on record.
Figure CC2: ACT mean minimum temperature anomaly (as calculated from the 1961 to 1990 average), 1926 to 2018.
Other annual temperature trends for the ACT include:
- an increase of 4 days per year for temperatures above 35 °C
- a decrease of 20 days per year for temperatures below 10 °C
- an increase of 20 nights per year for temperatures above 15 °C
- a decrease of 25 nights per year for temperatures below 0 °C
- autumn mean maximum temperatures have risen by just over 1.5 °C since 1926
- the warmest daytime temperatures for autumn were recorded in 2016, with 2018 the second warmest
- autumn mean minimum temperatures have risen by around 1 °C since 1926
- spring mean maximum temperatures have risen by over 1.5 °C since 1926, and
- spring mean minimum temperatures have risen by over 2 °C since 1926.
These results demonstrate a clear warming climate trend in the ACT. The impacts of this warming are discussed in Indicator CC2: Impacts of climate change.
There is considerable year-to-year and decadal variability in annual rainfall averaged over the ACT region, with no long-term trend (Figure CC3). Over the last two decades, the Millennium Drought drove drier-than-average conditions across the ACT from 2000–2009, before being broken by the two La Niña events of 2010–2011 and 2011–2012. Recent years have been drier than average, except for 2016 which had a strong negative Indian Ocean Dipole in that year which typically results in wetter than average conditions over south-eastern Australia.
Figure CC3: ACT annual rainfall anomaly (as calculated from the 1961 to 1990 average), 1900 to 2018.
Projected climate trends
Regional climate modelling has identified the most significant effects of climate change on the ACT. EPSDD, 2019, ACT Climate Change Strategy 2019–25, ACT Government, Canberra Webb, L.B. and K. Hennessy, 2015, Projections for Selected Australian Cities, CSIRO and Bureau of Meteorology, Australia These projections are dependent on the level of global greenhouse gas emissions. Projected impacts include:
- reduced rainfall, particularly for spring and winter rainfall, with more frequent and prolonged drought
- summer and autumn rainfall may remain unchanged
- extreme daily rainfall intensity is projected to increase
- average temperatures will continue to increase in all seasons
- increased extreme temperatures with up to an additional 5 hot days per year by 2030 and 20 more per year by 2070
- temperature increases will mainly be in spring and summer, although the number of hot days will also extend into autumn
- hotter temperatures (day and night), longer and more frequent heatwaves
- harsher fire-weather climate in the future,
- more frequent and severe storms over a longer summer season, with flash flooding, violent winds and thunderstorms
- fewer frosts, and
- increased evapotranspiration.
These projected changes will significantly increase climate pressures on the natural and urban environment.