A few weeks ago, as a cool change swept away Melbourne's mid-January heatwave, my partner and I went for a walk around our block. The air temperature had plummeted about ten degrees in 30 minutes, but as we passed a new two-storey home with no surrounding vegetation and a mound of gravel for a front lawn, I felt a surge of residual warmth. The house's dark-grey exterior seemed to shimmer with stored-up heat.
Hurrying on, I wondered how this house — and so many others like it — would cope with future heatwaves.
Climate change has loaded the dice towards hotter days and more frequent heat spells. Australia's average temperature has increased 0.9 degrees since 1910, while the number of record hot days has doubled since 1960. 'Although Australia has always had heatwaves, hot days and bushfires, climate change has increased the risk of more intense heatwaves and extreme hot days, as well as exacerbated bushfire conditions,' explained the Climate Commission's 2013 report 'Off the Charts: Extreme Australian summer heat'.
Heatwaves don't create the same dramatic news footage as bushfires, floods and cyclones, but they kill more people. From 1844 to 2010, heatwaves were responsible for at least 5332 deaths in Australia, and since 1900 they've killed more Australians than all other natural hazards combined. The January 2009 heatwave in Victoria, when Melbourne sweltered through three consecutive days of temperatures above 43 degrees, resulted in 374 deaths. In comparison, the Black Saturday fires took 173 lives.
While peak temperatures fell short of the 2009 heatwave, the severely hot weather across south-eastern Australia from 13 to 18 January this year lasted longer in many places. Adelaide had a record five consecutive days of 42 degrees and above, and Canberra had a record four consecutive days of 39 degrees. Sydney was spared the worst of the heatwave this time around, but last January the city registered its hottest day on record.
Meanwhile, Victoria had a record-breaking average maximum temperature of more than 41 degrees across four successive days, resulting in 139 'excess' deaths in the period up to 23 January.
The elderly are more vulnerable to extreme heat, and Australia's ageing population means we can expect the death toll to rise in the future. But the biggest impact will come from climate change. A November 2011 report from PricewaterhouseCoopers modelled the effect of future heatwaves on Melbourne and found that, by 2050, climate change could multiply annual average