As Queenslanders continue to wade through the mud, Premier Anna Bligh has started the process of finding answers in the aftermath of the floods by calling a commission of inquiry, but the wide-ranging terms of reference appear to have given little, if any, explicit consideration of the role of climate change.
This is a strange omission, given that only three months ago the state published its latest assessment of the potential impacts of climate change.
“Climate change is also likely to affect extreme rainfall in south-east Queensland,” the report said, adding that “a projected decrease in rainfall across most of Queensland, the projected increase in rainfall intensity could result in more flooding events.”
Among the terms is a request to the commission to make recommendations to improve the “preparation and planning for future flood threats and risks”, particularly when it comes to saving lives.
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Last year Queensland had its wettest year on record, but the spring period leading up to the flooding in the Rockhampton and Bundaberg areas and then in Brisbane, was exceptional. The state got 248 millimetres of rainfall — almost triple the statewide long-term average.
A separate Queensland government report into rainfall intensity, commissioned to provide advice to policy makers on inland flooding risks, also agreed that “the available scientific literature indicates this increased rainfall intensity to be in the range of 3%–10% per degree of global warming.”
But if these are the risks for Queensland it doesn’t necessarily implicate climate change in the line-up of suspects likely to be paraded before the public in coming months.
Several climate scientists are already discussing the role of increased atmospheric greenhouse gases in the atmosphere, caused mainly by the burning of fossil fuels such as coal and oil, and how it impacts extreme weather events.
Dr David Jones, head of climate monitoring and prediction at the Bureau of Meteorology, says there will be “a healthy scientific debate in the next few years about the point when the probability of an event was so implausibly small before climate change”.
“The signal-to-noise ratio is so high,” says Dr Jones, referring to the difficulty in picking out the climate change influence among the natural variability of weather and climate.
“The general view is that this is one of the strongest La Nina we have had in modern history where we have data going back to the early 1900s.
“The ocean temperatures last year were the highest on record and we know the oceans around Australia are warming quite quickly and that’s the fuel for the storms and rain events. In 2010 we had the highest humidity on record and July to October was our wettest ever.”
Dr Jones adds: “We have got extreme natural variability in La Nina which makes things confused, but we are seeing signatures of global warming in the climate system over Australia. We have the highest sea-surface temperatures on record with high humidity.
“The potential intensity of rainfall goes up with rising humidity. When people estimate what the likely maximum rainfall that can occur, one variable is the amount of moisture in the atmosphere. That’s well established.”
Professor Matthew England, co-director of University of New South Wales Climate Change Research Centre, is reluctant to explicitly apportion any of the flood crisis to climate change.
But he stresses that “to exclude climate change would be premature”.
Earlier this week, he told Reuters: “I think people will end up concluding that at least some of the intensity of the monsoon in Queensland can be attributed to climate change. The waters off Australia are the warmest ever measured and those waters provide moisture to the atmosphere for the Queensland and northern Australia monsoon.”
Speaking to Crikey, Professor England explained the waters to the north of Australia have warmed by about 0.5 degrees over the past 50 years.
Those waters are currently about 1.5 degrees warmer than average, he said, so it’s likely that about a third of this warming is due to long-term ocean temperature increases, the remainder due to the normal La Nina cycle.
“The warmth of the waters north of Australia drive our summer monsoon system via evaporation — the warmer the oceans are the greater the resulting moisture content of the atmosphere. In short, a warmer ocean north of Australia means increased monsoon rains.”
Professor England added that over the next 20-30 years, it was predicted that this same ocean region would warm by a further half a degree.
Professor Will Steffen, the science adviser to the Federal Department of Climate Change, has announced he will compile a report on the floods for the Gillard government’s multiparty climate change committee, of which he is a member.
One of Australia’s leading climate researchers, Professor Neville Nicholls, of Monash University and president of the Australian Meteorological and Oceanographic Society, told Crikey that in terms of the impact of climate change on Queensland floods “the simple answer is that we really don’t know”.
He agrees that the core driver of the deluge was the strong La Nina system. “The question is, is [climate change] exacerbating this? I would dearly like to find the answer to that.
“The IPCC has been projecting for a long time that as we get more warming we will get increased heavy rainfall.”
He said not enough studies had been done to have confidence about the role of climate change in single extreme weather events occurring now.
He added: “We should not confuse low confidence to mean that this is not happening. There are good grounds for believing that the warming is already affecting climate and things like heavy rainfall.”
Professor Ron Cox, of the UNSW School of Civil and Environmental Engineering, said: “The recent flood events in Queensland are a clear indication of the need for improved planning to adapt future development for our settlements and infrastructure. With expanding settlements, extreme weather resulting in emergency situations can be expected to become more frequent with higher temperatures and climate change.”
Dr Caroline Sullivan, associate Professor of Environmental Economics and Policy at Southern Cross University, added climate scientists around the world agreed that “extreme events are a likely outcome arising from climate change”.
She said: “There is currently so much evidence from across the world that global weather patterns are changing, it is not difficult to find many examples of extreme events.
“Let us once and for all learn from this, that climate change is real, and we must act now in a concerted fashion, before nature wreaks further havoc on our pitiful attempts to control it.”