Is global warming driving Australia's bushfires?

The deadly wildfires that tore across southeastern Australia this past week have prompted some experts to look beyond the arsonists, lightning strikes, and carelessly discarded cigarette butts to a more complex culprit: climate change.

While all agree that it is impossible to link any single event – no matter how extreme – to global warming, scientists say that the extreme heat and dryness that helped spread the fires are becoming more common as human activity continues to produce greenhouse gases.

According to the UN's Intergovernmental Panel on Climate Change's Fourth Assessment Report, released in 2007, heatwaves and brush fires are "virtually certain to increase in intensity and frequency" in Australia. Many parts of that country have been in the grips of a seven-year drought, the worst in recorded history.

As an article in Time magazine notes, in 2007 Australia's national science agency predicted that, if climate change continues unabated, by 2020 there could be up to two-thirds more "extreme fire-danger days" compared with 1990. The organization found that there could be up to a threefold increase in such days by midcentury.

[Update: Commenter Tenebris dug up the report, which I hadn't been able to find. You can read it here.]

Writing in the Guardian, Tim Flannery observes that Victoria, the state where the fires raged, has become hotter and drier in recent years. Mr. Flannery is a zoologist and conservationist at Sydney's University of Macquarie and author of "The Weather Makers: The History and Future Impact of Climate Change." He describes how Victoria's shifting winds and high temperatures, which this month have topped 115 degrees F., have in the past helped drive deadly brush fires.

"But this time the conditions were more extreme than ever before," he writes, "and the 12-year 'drought' meant that plant tissues were almost bone dry."

Flannery describes how his home state's climate has changed so drastically:

Scientists are famously wary of attributing single events to climate change. The Associated Press quotes two experts – a professor of agriculture and the head of Australia's national science advisory group – who say that no definitive link can be traced, but that climate change seems to be loading the dice:

Many news outlets covering the bushfires quote Bob Brown, the head of Australia's Greens party, who said the fires are a reminder of the dangers of climate change.

But climate activists who cite extreme weather events – if we can use that term to describe the bushfires – could be overplaying their hand, warns Vicky Pope, the head of the climate prediction program at Britain's Met Office. Writing in Wednesday's Guardian about exaggerations of melting Arctic ice, Ms. Pope says that reflexively attributing any bad weather to climate change is ultimately a disservice to science:

As this blog noted last month as particularly frigid temperatures descended on many parts of the United States, you can't tell much about climate change by looking only at a particular day, season, or year. But Australia's intense fires are very much in line with what climate scientists have predicted. These same scientists say that we can expect more fires like these, all over the world.