If global greenhouse gas emissions continue to grow quickly, average temperatures in Australia by 2070 are likely to be 2.2°C-5.0°C above 1990 levels, says a report released today by CSIRO and the Bureau of Meteorology. But if the world adopts a low emissions pathway, the rise could be limited to 1.0°C-2.5°C.
The report says that within these ranges the best estimate for 2070 under the high emissions scenario is 3.4°C and the best estimate for the low emissions scenario is 1.8°C.
In 2030, Australia will be an average 1°C warmer than it was in 1990 (with a range of uncertainty of 0.6°C to 1.5°C), the report says. Warming will be less pronounced in coastal areas (0.7°C-0.9°C) than inland (1°C-1.2°C). There will be changes in temperature extremes, with fewer frosts and substantially more days over 35°C.
Australia’s average temperatures have already increased by 0.9°C since 1950, though with significant regional variations, it says.
Rainfall declines
There have been “substantial rainfall declines” in Victoria, on the east coast and in south-west Australia, it says. In stark contrast, north-west Australia has experienced an increase in rainfall.
The report says global sea levels rose by about 17 centimetres during the 20th century. And it notes seawater near the bottom of the ocean off Antarctica has rapidly become less salty and less dense. “This freshening may be the signature of increased melt from Antarctic glaciers,” it says.
Rising concentrations of atmospheric carbon dioxide will cause increases in ocean acidity in the Australian region and this could affect the capacity of marine organisms to grow shells and endoskeletons, it says.
The report notes the latest projections have taken advantage of significant technical advances since CSIRO’s 2001 climate change projections. These include projections using a much larger number of climate and ocean variables and many more climate models.
Climate Change In Australia: Technical Report 2007 (CSIRO, Bureau of Meteorology, October 2, 2007)
Website with interactive regional maps (CSIRO, Bureau of Meteorology, October 2, 2007)
