More gloom on climate front

The deluges and floods that have inundated vast tracts of eastern Australia in the past two years have not affected accelerating trends that have pushed carbon dioxide levels to their highest in 800,000 years.

While the extreme rains have been dumped as a result of two successive la Nina events, the earth has continued heating at a rate that has seen each decade warmer than the preceding 10-year period since 1950.

And a new report from the federal science agency CSIRO and the Bureau of Meteorology says that average temperatures across Australia are expected to rise by up to 5C by 2070.

It says rising CO2 levels from the burning of fossil fuels continue to warm the continent's land and oceans.

This will bring more droughts and bushfires - but also an increase in intense rainfall in many areas.

Launching the two agencies' latest State of the Climate report yesterday, CSIRO chief executive Megan Clark said Australia's climate varied greatly from one year to the next, but long-term trends remained clear.

"Much of Australia may have lurched from drought to floods ... but this has occurred against a backdrop of steadily increasing air and ocean temperatures and rising sea levels," she said.

"What's more, the rate of change is increasing. The fundamental physical and chemical processes leading to climate change are well understood, and CSIRO and the Bureau of Meteorology observations demonstrate that change is occurring now."

The CO2 concentration of the atmosphere had risen to about 390 parts per million by 2011, with an increase of more than 3 per cent over the past decade projected to cause significant further global warming.

"The main cause of the observed increase in CO2 concentration in the atmosphere is the combustion of fossil fuels since the industrial revolution," the report says.

It says that over the past 60 years the number of warm nights has been increasing, with more monthly maximum temperatures being broken.

Since 1910, when accurate records began, Australia's average annual daily maximum temperatures have risen by 0.75C, and overnight minimums by more than 1.1C.

There is also a general trend towards increased spring and summer monsoonal rainfall across Australia's north, and a decline in late autumn and winter rainfall across southern Australia.

Sea levels have risen around the continent at rates equal to or greater than the global average, and sea surface temperatures in the region have increased faster than the global average, rising by about 0.8C since 1910 to their highest level on record in 2010.

The planet's average mean sea level last year was 210mm above 1880 levels, with sea levels rising faster between 1993 and 2011 than during the entire 20th century.

The report says that while both natural and human influences have affected climate over the past century, it was "very likely" that most of the surface global warming observed since the 1950s was because of human activity.

It says human activities have also influenced ocean warming, sea-level rise, and temperature extremes.

"The warming around Australia is consistent with the global pattern and cannot be explained by natural variability alone."