Australia — IN A land of droughts and flooding rains, it’s often hard to remember when you’re being scorched by one or submerged by the other. But lately Australia seems to be oscillating between increasingly regular and ruinous extreme weather events – and sometimes suffering the opposite ends of the extremes at the same time.
So one side of the continent is inundated by the worst floods in memory, while its south-west corner is hit by bushfires. Is this the future? Are these a sign of things to come with climate change?
The short answer, from a range of experts consulted by The Sunday Age, is yes and no.
Professor Andy Pitman, of the University of NSW’s Climate Change Research Centre, suggests there isn’t a scientist in the country who would pin all the blame for Queensland’s floods or Victoria’s inundating rains on climate change. That rests with the little girl – La Nina, the periodic ocean-atmosphere weather phenomenon that cools the eastern and central Pacific and brings wetter than usual weather to Australia.
Dr David Jones, climate analyst with the Bureau of Meteorology agrees. ”The last year (of extreme weather events across the world) certainly has been really extreme, but in the Australian context the really major story is La Nina,” he says. ”It’s one of the strongest in recorded history.”
The last comparable La Nina, from 1973 to 1975, brought similar calamity, he notes, including the record Brisbane floods and cyclone Tracy of 1975. La Ninas in 1955 and 1917 also brought major flooding.
But this La Nina has been exacerbated by record-high sea surface temperatures and those might well be a result of global warming. How much they have driven the intensity of the last year’s rains (and 2010 was Australia’s third wettest on record) and whether global warming is causing more intense La Ninas and their opposite, El Ninos, which bring drought to Australia, is still unknown.
”The warming we’ve seen over the last 30 or 40 years, of about half a degree, has to have an effect on changing the background climate on which natural variabilities such as La Ninas and El Ninos operate,” says Monash University meteorologist Professor Neville Nicholls. Unfortunately, no one has a computer big and fast enough, nor enough money to run the sort of models that could confirm the link or predict any effect into the future, he says.
”We certainly can’t say thereis or isn’t a global warming signal because the work’s not been done,” says Professor Pitman. ”Scientists just can’t say yea or nay. The actual analysis has to be done and, boringly, that takes a very long time.” But there are so many extreme weather events happening, and at such an unusual frequency, one has to be ”extremely suspicious” that there is some connection, he says.
Professor Will Steffen, executive director of the Australian National University’s Climate Change Institute, says there’s ”definitely” a growing risk that events of this type will become more frequent as the climate warms. ”One-in-100-year events would become a one-in-20 or one-in-30-year event as the climate shifts we say with some confidence they are becoming more frequent and they will become more frequent in future.”
Dr Kevin Tolhurst, Melbourne University fire ecologist, notes that, basically, what drives the world’s weather systems is heat and a lot of that comes from the sun. ”The consequence of global warming is like putting your foot harder on the accelerator, you still have variation, you still go up and down hills. But you’ve got more energy in the system to push in both directions, so you go down hills faster and you go higher up the hills.”
Certainly, the world appears to have increasingly suffered wild and damaging swings in its weather in recent years, from the record high temperatures and bushfire havoc of Black Saturday in February 2009 to monsoonal flooding in January 2011, from scorching Russian summer to recently snowbound Europe and North America.
Global reinsurance giant Munich Re recently plotted 950 natural catastrophes over 2010. It found more than 90 per cent were weather-related – with a cost of more than $US130 billion and a huge loss of life. It estimated the Russian heatwave and associated fires and air pollution in July killed at least 56,000 people and Pakistan’s worst-ever floods killed 1769.
Worldwide, 2010 was the wettest on record but, according to the World Meteorological Organisation, also the hottest since instrumental climate records began in 1850. Eighteen nations experienced their hottest-ever temperatures. It was the coolest year in Australia since 2001 but still above the long-term average.
Professor Nicholls says that while it is not possible to accurately predict global warming-induced changes to natural variables like La Nina, one prediction can be made with confidence – heatwaves.
”The last 10 years has been the decade of unprecedented heatwaves around the world,” he says. ”A whole string of heatwaves much more dramatic than we’ve seen before and they’ve been killer heatwaves.”
The last three days of January 2009, in the week before Black Saturday (at 46.4 degrees, itself the hottest February day in Melbourne by more than three degrees) there were 374 extra deaths in Victoria due to the heatwave, he says.
Dr Tolhurst says we can also expect more fires. In Victoria, about 27 per cent of bushfires in the past 30 years have been started by lightning. Because of inaccessibility and multiple strikes causing separate fires to converge, the area burnt is about 70 per cent of the total. But lightning-sparked fires have been increasing. In 2003 and 2007 they accounted for about 40 per cent of all bushfires.
University of Southern Queensland climatologist Professor Roger Stone, director of the Australian Centre for Sustainable Catchments and chairman of a United Nations global team investigating the impacts of climate change and extreme weather on agriculture, says the see-saw pattern of changes between La Ninas and El Ninos would have a significant future impact on Australia’s economy.
”These events can often reduce GDP growth by half of 1 per cent because they have a huge impact on our mining industry, agriculture, tourism, insurance companies someone has to pay for this at the end of the day.”
Professor David Karoly, from Melbourne University’s school of earth sciences, agrees: ”In terms of planning for these events, we need to develop adaptation measures that cope with even greater variability in rainfall in Australia. So hotter and drier conditions in some years and very wet conditions in other years,” he says. ”We need to be able to cope with Australia becoming a land of more droughts and worse flooding rains.”