An increase in the mean temperature in Australia of about 0.7 °C (1.26 °F) since 1960 and other observed changes in rainfall, sea level rise, ocean acidification and atmospheric CO2 concentration show that “climate change is real”, according to a joint CSIRO/Bureau of Meteorology (BOM) statement and snapshot of the state of the country’s climate. CSIRO, Australia’s national science agency, and the Bureau of Meteorology are the country’s two lead climate science agencies.
The snapshot is sourced from peer reviewed data on temperature, rainfall, sea level, ocean acidification, and carbon dioxide and methane levels in the atmosphere.
Australia holds one of the best national climate records in the world. The Bureau’s been responsible for keeping that record for more than a hundred years and it’s there for anyone and everyone to see, use and analyse.
—Dr. Greg Ayers, BOM Director
Changes observed include:
Temperature. Since 1960 the mean temperature in Australia has increased by about 0.7 °C . The long term trend in temperature is clear, but there is still substantial year to year variability of about plus/minus 0.5 °C (0.9 °F). Some areas have experienced a warming of 1.5 to 2 ºC (2.7 °F to 3.6 °F) over the last 50 years. Warming has occurred in all seasons, however the strongest warming has occurred in spring (about 0.9 °C, 1.62 °F) and the weakest in summer (about 0.4 °C, 0.72 °F).
The number of days with record hot temperatures has increased each decade over the past 50 years, while there have been fewer record cold days each decade. 2000 to 2009 was Australia’s warmest decade on record.
Rainfall. While total rainfall on the Australian continent has been relatively stable, the geographic distribution of rainfall has changed significantly over the past 50 years. Rainfall decreased in south-west and south-east Australia, including all the major population centers, during the same period.
Sea-level rise. Rapidly rising sea levels from 1993 to 2009, with levels around Australia rising, between 1.5mm and 3mm (0.059" to .118") per decade in Australia’s south and east and between 7mm and 10mm (.276" to .394") in the country’s north.
Sea surface temperatures. Sea surface temperatures around Australia have increased by about 0.4°C (0.72 °F) in the past 50 years.
Ocean acidification. The world’s oceans currently absorb about 25% of the carbon dioxide generated by humans—with about 40% of this being absorbed in the Southern Ocean. The CO2 absorbed by the ocean makes the ocean become more acidic. Recent research shows that ocean acidification decreases the ability of marine plants and animals to form shells. Such effects are now being observed at the base of the food chain in the Southern Ocean.
Australian average temperatures are projected to rise by 0.6 to 1.5 ºC [1.08 to 2.7 °F] by 2030. If global greenhouse gas emissions continue at current levels, warming is projected to be in the range of 2.2 to 5.0 ºC [3.96 to 9 °F] by 2070. Warming is projected to be lower near the coast and in Tasmania and higher in central and north-western Australia. These changes will be felt through an increase in the number of hot days.
In Australia compared to the period 1981-2000, decreases in rainfall are likely in the decades to come in southern areas of Australia during winter, in southern and eastern areas during spring, and in south-west Western Australia during autumn. An increase in the number of dry days is expected across the country, but it is likely that there will be an increase in intense rainfall events in many areas.
There is greater than 90% certainty that increases in greenhouse gas emissions have caused most of the global warming since the mid-20th century. International research shows that it is extremely unlikely that the observed warming could be explained by natural causes alone. Evidence of human influence has been detected in ocean warming, sea-level rise, continental-average temperatures, temperature extremes and wind patterns. CSIRO research has shown that higher greenhouse gas levels are likely to have caused about half of the winter rainfall reduction in south-west Western Australia.
State of the Climate (March 2010)