This summer, life in Australia resembles a compulsory and very unpleasant game of Russian roulette. A pool of hot air more than 1,600km wide has formed across the inland. It covers much of the continent and has proved astonishingly persistent. Periodically, low pressure systems spill the heat toward the coast, where most Australians live. At Christmas it was Perth. Then the heat struck Adelaide, followed by Tasmania, Victoria and southern New South Wales and Canberra. Over the weekend, it was southern Queensland and northern New South Wales that looked set to face the gun, and with every heat wave, the incidences of bushfires and heat-related deaths and injuries spike.
Australians are used to hot summers. They normally love them. However, the conditions prevailing now are something new. Temperature records are being broken everywhere. At Leonora, in the Western Australian interior, it reached 49?C last week — just one record among many. The nation’s overall temperature record was set on Monday last week. Then the following day, that record was exceeded.
The breaking of so many records indicates that Australia’s climate is shifting. This is supported by analysis of the long-term trend. Over the past 40 years Australia has seen a decline in the number of very cold days and the occurrence of many more very hot days. All of this was predicted by climate scientists decades ago and is consistent with the increasing greenhouse gas concentration in the atmosphere.
The new conditions have seen the Bureau of Meteorology add two new color categories to Australia’s weather prediction maps. Temperatures of 48?C to 50?C used to be the highest, and where such extremes were anticipated, the weather map was marked black. Over the last week, purple patches have begun to appear on some maps. They mark temperatures above 50?C. Pink, which is yet to be deployed, will denote temperatures above 52?C.
Climate extremes have a way of stacking up to produce unpleasant consequences. Two years ago, the ocean temperature off northwestern Australia reached a record high, and evaporation of the seawater led to Australia’s wettest year on record. This was followed in central Australia by the longest period without rain on record. The vegetation that had thrived in the wet now lies dried and curing, a perfect fuel for fires.
With abundant fuel and increased temperatures, the nature of bushfires is changing. Australians have long rated fire risk on the MacArthur index. On it, a rating of 100 — the conditions that prevailed in the lead-up to the devastating 1939 bushfires — represents “extreme” risk, but after the 2009 fires, a new level of risk was required.
“Catastrophic” represents a risk rating above 100. Under such conditions fires behave very differently. The Black Saturday fires of 2009, which killed 173 people, were rated at between 120 and 190. They spread so fast and burned so hot that the communities they advanced upon were utterly helpless.
The superheated air currently monstering the continent is fickle. Last week, Sydney residents watched in relative thermal comfort as those living just 100km to the south endured scorching heat, blustering winds and unstoppable fires. The forecast for coming days indicates that Sydney might once again be lucky, with the worst fire conditions striking 50km to the north of the city. However, things might work out differently.