Professor Gerald Nanson
A number of media commentators and numerous letters to the editors in major newspapers have suggested that the recent floods in Queensland are some sort of bellwether of global warming and Australia’s hazardous climatic future in a warming world. There is no doubt the globe has been warming over the past century or so, and it seems very likely that this is a function, at least in part, of our introduction of excessive Greenhouse gases to the atmosphere. But Australian weather is far too variable today, and indeed has been so for thousands of years, to enable any confident predictions to be made about the changing magnitude and frequency of extreme events. The last major flood on the Brisbane River was in 1974 which coincided in many places with the most extreme flood events continent-wide since European arrival. So while we have just two such truly ‘catastrophic’ flood events in our recorded history, it is very difficult to say anything scientifically sound about their changing magnitude and the likely frequency of their occurrence. Scientists sometimes use smaller events analysed statistically to predict the likely size and frequency of extreme events, but Australian climate is well known to move in cycles, several decades in length, which commonly result in clusters of decades producing very different conditions to those before and after. Indeed, our natural climate is something of a rollercoaster ride. When ‘old timers’ timers say that a particular flood is the largest they have ever seen in their area, it isn’t necessarily because climate is changing, it’s mostly because even ‘old timers’ don’t live for hundreds of years. Global movement of the ‘climate goalposts’ can be used as an excuse for poor urban regional planning. There is abundant evidence of extreme flood risk in many areas of Australia, including in Brisbane, and much of this evidence was collected before global warming was an additional significant variable to consider. The human cost of flooding in Australia is mostly the product of poor planning, not climate change.
Professor Gerald Nanson is from the UOW School of Earth and Environmental Sciences
Read another short essay from Gerald :
“The floods of Queensland have raised important issues relating to how well Australia collects data that is vital for the accurate analysis of potential hazards, and how adequately our country understands and therefore is prepared to deal with our extreme environmental hazards.” More at: http://media.uow.edu.au/news/UOW094233.html
