Australia's blistering heatwaves here to stay

Last updated 07:30 09/01/2013
Sydney heatwave
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EARLY BURN: Runners get out early to beat the head at Sydney's Bronte Beach.

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The heatwave that has scorched Australia since Christmas is a taste of things to come, with this week's records set to tumble again and again in the coming years, climate scientists say.

The hottest average maximum temperature ever recorded across Australia - 40.33 degrees Celsius, set on Monday - might stand for only 24 hours and be eclipsed when all of yesterday's readings come in.

The previous record had stood since December 21, 1972.

» Australia’s heatwave sparks bushfires

''The current heatwave - in terms of its duration, its intensity and its extent - is unprecedented in our records,'' said the Bureau of Meteorology's manager of climate monitoring and prediction, David Jones.

''Clearly, the climate system is responding to the background warming trend. Everything that happens in the climate system now is taking place on a planet which is a degree hotter than it used to be.''

As the warming trend increased over coming years and decades, record-breaking heat would become more common, Dr Jones said.

''We know that global climate doesn't respond monotonically - it does go up and down with natural variation. That's why some years are hotter than others because of a range of factors. But we are getting many more hot records than we're getting cold records. That's not an issue that is explained away by natural variation.''

Australia's climate is based on an interplay of many factors, including regional and local weather patterns, El Nino and La Nina climate cycles and the Indian Ocean dipole, all superimposed on the greenhouse gas-driven warming trend.

While temperatures vary on a local and regional scale, globally it has been 27 years since the world experienced a month that was colder than average.

The impacts of the rising heat on farming, food, water and human health have been studied closely for years, and the trends being played out now mirror those laid out years ago in projections by the bureau, the CSIRO and the Garnaut climate change review.

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They include heightened bushfire risk, rising sea levels affecting infrastructure and houses all along the coast and, by the end of the century, massive cuts in food production in the Murray-Darling Basin.

According to a peer-reviewed study by the Australian-based Global Carbon Project, global average temperatures are on a trajectory to rise a further four to six degrees by the end of this century, with that rise felt most strongly over land areas.

It would be enough to tip Tuesday's 40C-plus temperatures over much of mainland Australia close to 50C in some parts.

"Those of us who spend our days trawling - and contributing to - the scientific literature on climate change are becoming increasingly gloomy about the future of human civilisation,'' said Liz Hanna, convener of the human health division at the Australian National University's climate change Adaption Network.

''We are well past the time of niceties, of avoiding the dire nature of what is unfolding, and politely trying not to scare the public,'' Dr Hanna said. ''The unparalleled setting of new heat extremes is forcing the continual upwards trending of warming predictions for the future, and the time scale is contracting.''

Around the world, this year could be the hottest ever recorded by modern instrumentation, according to a recent study by Britain's Met Office.

It said that, based on the rising background warming trend, this year would be 0.43 to 0.71 degrees hotter globally than the average temperature between 1961 and 1990, with a ''best fit'' of 0.57 degrees warmer. If that turns out to be accurate, this year would surpass the previous record, held jointly by 2005 and 2010.

The Met Office findings are considered telling in the climate science community, because this year is set to be a relatively ''neutral'' year, without a strong El Nino warming cycle to push up temperatures.

The current Australian heatwave, while exceptional, is a continuation of the record-breaking temperatures seen across much of Australia since September, according to the special climate statement issued by the bureau on Tuesday. The last four months of last year were the hottest on record, albeit by just 0.01 of a degree.

''This event is ongoing with further significant records likely to be set,'' the statement said.

The weather bureau's Dr Jones said the background warming was now clearly felt.

''Our oceans are hotter, the tropics are hotter, so any attempt to disentangle climate change from what we see in terms of weather doesn't make much sense - everything is hotter,'' he said.

''There is no alternative world which doesn't have the fingerprint of warming.''

- Sydney Morning Herald

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