State of the Climate - 2012

Temperature

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Key points

  • Each decade has been warmer than the previous decade since the 1950s.
  • Australian annual average daily maximum temperatures have increased by 0.75 °C since 1910.
  • Australian annual average daily mean temperatures have increased by 0.9°C since 1910.
  • Australian annual average overnight minimum temperatures have warmed by more than 1.1 °C since 1910.
  • 2010 and 2011 were Australia’s coolest years recorded since 2001 due to two consecutive La Niña events.

Australian average temperatures over land

Australian annual average daily mean temperatures showed little change from 1910 to 1950 but have progressively warmed since, increasing by 0.9 °C from 1910 to 2011. The average temperature during the past ten years has been more than 0.5 °C warmer than the World Meteorological Organization’s standard 1961-1990 long-term average. This increase continues the trend since the 1950s of each decade being warmer than the previous.

The warming trend has occurred against a backdrop of natural, year-to-year climate variability. Most notably, El Niño and La Niña events during the past century have continued to produce the hot droughts and cooler wet periods for which Australia is well known. 2010 and 2011, for example, were the coolest years recorded since 2001 due to two consecutive La Niña events.

Graph showing temperature anomalies.

Changes in average temperature for Australia for each year (orange line) and each decade (grey boxes), and 11-year average (black line – an 11-year period is the standard used by the Intergovernmental Panel on Climate Change). Anomalies are the departure from the 1961-1990 average climatological period. The average value for the most recent 10-year period (2002–2011) is shown in darker grey.

A graph showing the increase in annual average daily mean temperature from 1960 to 2011 (in °C)

Increase in annual average daily mean temperature from 1960 to 2011 (in °C). Most of Australia has experienced warming over the past 50 years, with some areas experiencing warming since 1960 of up to 1 °C.

 

Australian annual average daily maximum temperatures have increased by 0.75 °C since 1910, with most of the warming trend occurring since 1970. There has been an increase in the frequency of warm weather and decrease in the frequency of cold weather.

Consecutive La Niña events in the past two years, however, have kept average maximum temperatures below the long-term average – by 0.24 °C in 2010 and 2011. Very few extreme hot maxima were recorded during these two years, with the exception of three heat waves in 2011 in southeast Western Australia and central South Australia in January and February, southeast Australia in August, and in northwest Western Australia in December.

Australian annual average overnight minimum temperatures have warmed more rapidly than daytime maximum temperatures. Minimum temperatures have warmed by more than 1.1 °C since 1910 – with more than 0.8 °C of that warming occurring since 1960.

The number of climate reference stations recording warm (top ten per cent) night-time temperatures and the frequency with which this occurs have increased since the mid 1970s. The rate of very hot (greater than 40 °C) daytime temperatures has been increasing since the 1990s. The frequency of extreme (record) hot days has been more than double the frequency of extreme cold days during the past ten years.

A graph showing the number of hottest-day-of-the-month records from 1910

Number of hottest-day-of-the-month (highest maximum) records at 43 Australian climate reference stations with daily data from 1910; for each year (orange line) and each decade (grey boxes), and the 11-year average (black line). The average for the most recent 10-year period (2002-2011) is shown in darker grey.

 

A graph showing the number of coldest-day-of-the-month records from 1910

Number of coldest-day-of-the-month (lowest maximum) records at 43 Australian climate reference stations with daily data from 1910; for each year (orange line) and each decade (grey boxes), and the 11-year average (black line). The average for the most recent 10-year period (2002-2011) is shown in darker grey.

 

Rainfall

Key Points

  • Southwest Western Australia has experienced long-term reductions in rainfall during the winter half of the year.
  • There has been a trend over recent decades towards increased spring and summer monsoonal rainfall across Australia’s north; higher than normal rainfall across the centre, and decreased late autumn and winter rainfall across the south.

Australia’s rainfall is highly variable. During recent decades, there has been a general trend towards increased spring and summer monsoonal rainfall across Australia’s north, higher than normal rainfall across central parts of the continent, and decreased late autumn and winter rainfall across the south.

A very strong La Niña event in 2010, followed by another La Niña event in 2011, brought the highest two-year Australian-average rainfall total on record. Many rainfall records were broken during this period.

Southwest Western Australia experienced its lowest rainfall on record in 2010 and only average rainfall during 2011, in contrast to the rest of the continent. 

The record rainfall of 2010 and 2011 fell in spring and summer in the southeast of the continent. Rainfall was below average for the period April to July 2011, continuing the longer-term drying trend observed over the winter half of the year for this region. Recent drying trends across southern Australia in autumn and winter have been linked to circulation changes. The causes of these changes are an area of active research.

A map of Australia showing rainfall deciles from 1997 to 2011

April to September (autumn and winter) rainfall deciles from 1997 to 2011 for Australia (a decile rainfall map shows whether the rainfall is above average, average or below average for the most recent 15-year period, in comparison with the entire rainfall record from 1900). Areas of highest on record and lowest on record are also shown.

 

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