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Tuesday, January 8, 2013
Get used to record-breaking heat: bureau
Ben Cubby Environment Editor The Age,January 9, 2013
The heatwave that has scorched the nation 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 said.
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.
The hottest average maximum temperature ever recorded across Australia – 40.33 degrees, set on Monday – may only stand for 24 hours and be eclipsed when all of Tuesday's readings come in. Previously, that record had stood since December 21, 1972.
''The current heatwave – in terms of its duration, its intensity and its extent – is now unprecedented in our records,'' the Bureau of Meteorology's manager of climate monitoring and prediction, David Jones, said.
''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 increases over coming years, record-breaking heat will become more and 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're 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 now 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 of Meteorology, the CSIRO and the Garnaut climate change review.
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 over-40 temperatures over much of mainland Australia very close to 50 degrees 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 Adaptation 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. The unparalleled setting of new heat extremes is forcing the continual upwards trending of warming predictions for the future, and the timescale is contracting.''
Around the world, 2013 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, 2013 will be 0.43 degrees 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, 2013 would surpass the previous record, held jointly by 2005 and 2010.
The Met Office findings are considered telling in the climate science community, because 2013 is set to be a relatively ''neutral'' year, without a strong El Nino warming cycle to push temperatures up.
The Australian heatwave, which is 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 2012 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.