23 March 2010 – Australia’s two lead climate science agencies – the CSIRO and Bureau of Meteorology – have produced a snapshot of the state of the climate. Following are key points:
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.
Some areas have experienced a warming of 1.5 to 2 ºC over the last 50 years. Warming has occurred in all seasons, however the strongest warming has occurred in spring (about 0.9 °C) and the weakest in summer (about 0.4 °C).
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 centres, during the same period.
From 1870 to 2007, the global average sea level rose by close to 200mm. Sea levels rose at an average of 1.7mm per year during the 20th century and about 3.0mm per year from 1993-2009. These levels are global averages and because of the differing movements of ocean currents around the globe, results vary from place to place. This is true for Australia where since 1993 levels have risen 7-10mm per year in the north and west, and 1.5-3mm in the south and east.
Global CO 2 concentrations have risen rapidly over the last century. Methane, which is another greenhouse gas, has shown similar increases. The carbon dioxide concentration in 2009 of 386 parts per million (ppm) is much higher than the natural range of 170 to 300 ppm that has existed in the atmosphere for at least the past 800,000 years and possibly the past 20 million years.
What this means.
Australia will be hotter in coming decades Australian average temperatures are projected to rise by 0.6 to 1.5 ºC by 2030. If global greenhouse gas emissions continue to grow at rates consistent with past trends, warming is projected to be in the range of 2.2 to
5.0 ºC 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.
Much of Australia will be drier in coming decades
In Australia compared to the period 1981-2000, decreases in rainfall are likely in the decades to come in south-western 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.
It is very likely that human activities have caused most of the global warming observed since 1950 There is greater than 90 per cent 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.
Climate change is real
Observations clearly demonstrate that climate change is real. CSIRO and the Bureau of Meteorology will continue to provide observations and research so that Australia’s responses are underpinned by science of the highest quality.