In a joint statement released earlier this week, CSIRO and the Bureau of Meterology (BoM) outlined afresh the underlying fact that Australia’s climate has warmed since the late 1950s, in accord with the global average, and that warming can be “very likely” attributed to human activity.

The six-page statement concisely presented the likely indicators of human-induced climate change:

• across Australia, temperature stations have recorded warming over the past 50 years. In some areas, including south-east Queensland, the Corner Country and central Australia, the warming amounts to 1.5°C to 2°C over five decades.
• new research shows that the number of days with record warm temperatures has more than doubled, while the number of days with record cold temperatures has more than halved.
• over the past 40 years, Australian rainfall patterns have changed. Average annual rainfall in south-eastern Australia, the Murray-Darling Basin and eastern Queensland has declined, by up to 40 mm per decade in some areas. Rainfall in north-western Australia has increased by a similar proportion.
• since 1993, sea levels around Australia have risen by 1.5 to three millimetres per year in the south, and 7-10 mm in the north. Since 1870, sea levels have risen by about 200 mm.
• sea surface temperatures have increased by about 0.4°C in 50 years.
• oceans absorb about 25 per cent of the carbon dioxide generated by humans, and about 40 per cent of this is absorbed by the Southern Ocean. CO2 makes oceans more acidic, inhibiting shell formation on marine animals—an effect already being observed in the ocean food chain.
• in 2009, atmospheric carbon dioxide levels reached 386 parts per million, well outside the natural range that has existed for at least the past 800,000 years, and possibly the past 20 million years.
• methane levels in the atmosphere have more than doubled since 1800.

“Climate change is real,” the statement concluded.

It repeated the Intergovernmental Panel on Climate Change’s (IPCC’s) conclusion that there is greater than 90 per cent certainty that increases in greenhouse gas emissions have been responsible for the warming observed since the middle of last century.