Heatwaves an ominous sign

November 25, 2009

Adelaide's Central Bus Station is an austere but pleasing building built recently near the middle of town. No longer merely for coach travellers, the structure is now to be Adelaide's version of the New Orleans Superdome — a place of public refuge from what threatens, in time, to be another full-scale natural catastrophe.

The air-conditioned bus station is now kept open 24 hours a day, with cold water supplied, to give relief to city residents at risk from the latest of Adelaide's now alarmingly frequent heatwaves.

On November 8, the temperature in the city reached 37°Celsius. Not unusual for Adelaide at this time of year — but the superheated days have kept piling upon one another.

As I write, the temperature outside is almost 40°C, and daily highs have exceeded 35°C for eight days straight. The old record for November was four days.

And it's still only spring. Like many South Australians, I grew up with tales of the heatwave of January 1939. Until recent years, that was the only time eight consecutive days above 35°C had been recorded.

Then in March 2008 — autumn — came a heatwave lasting 15 days. Meteorologists calculated if it were purely the result of chance, it would have been a once-in-3000-years event.

Within a year, beginning in late January 2009, came six consecutive days over 40°C. And now, Adelaide is experiencing its first-ever spring heatwave.

Step out the door, and it seems as if the air is trying to knock you over. A burning pain surrounds your eye-sockets.

Climate change deniers — and the city still has some — will no doubt be crouched beneath their air conditioners, reading the Murdoch press as it ridicules the inability of climate scientists to predict outcomes in exact detail.

And it's true: Adelaide's weather of the past few years, in which spring and autumn seem only memories, was not precisely foreseen by anyone. But to the extent that the predictions have been wrong, the errors lie in being nowhere near as extreme as the reality.

To give the climate scientists their due, they now have a robust understanding of the key cause behind Adelaide's rash of heatwaves.

That cause, itself a clear consequence of global warming, is a strengthening of the mid-latitude high-pressure ridge, the "highs" that drift across the weather maps.

Even in summer, it used to be unusual for more than a few days to pass in Adelaide without a cool change from the Southern Ocean bringing temperatures down. Now, rising air pressure south of the continent means weeks can pass without relief.

"Adelaide's unprecedented November heatwave", a press statement from South Australia's Climate Emergency Action Network said, "is classic climate change weather."

As in New Orleans, the prime victims of this calamity are the old, poor and sick. During the January heatwave, the South Australian coroner received reports of 58 deaths in which heat was a factor.

So what are the city and state authorities now doing apart from keeping the bus station open?

The state Labor government of Premier Mike Rann has set itself the goal of "leading the nation in tackling climate change", and in various ways is achieving this objective.

South Australia has a target of "reducing emissions by 60% (to 40% of 1990 levels) by 2050". But the most recent science, from the Potsdam Institute for Climate Impact Research in Germany, points to much greater challenges.

If humanity is to have much chance of keeping global temperature rises below 2°C, big polluters like Australia will need to stabilise net emissions within the next few years, then cut them to zero by mid-century.

On top of this, nations like Australia will have to implement huge foreign aid programs focused on developing zero and low-emissions energy technology.

If the Rann government is really to lead the nation in tackling climate change, it will need to transform its thinking and actions in line with this goal.

In October, the British Meteorological Office predicted that, without determined action to reduce carbon emissions, average global temperatures would most likely reach 4°C above pre-industrial levels by 2050.

For inland Australia — which, whenever the wind blows from the north, in effect includes Adelaide — the most likely increase is given as 5-6°C. By mid-century, this indicates, the hottest days in Adelaide would reach 50°C.

Adelaide's heatwaves are an ominous signal that dangerous climate change has already begun. South Australia's settled areas need not, of course, finish up as super-hot desert; global carbon emissions could still be reined in.

But when the powerful fail to recognise the looming catastrophe, even in the blast that hits them when they walk out the door on a spring morning, it does not inspire confidence.

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