EVER the opportunist, Bob Brown, Leader of the Australian Greens, yesterday blamed the Brisbane floods on the coal industry for causing global warming.
But there is no correlation between atmospheric levels of carbon dioxide and rainfall or flooding, as measured by the Australian Bureau of Meteorology, anywhere in Australia.
There is, however, a correlation between patterns in the major atmospheric-oceanic oscillations and flood events.
Stewart Franks, a hydrologist at the University of Newcastle, has shown that the usefulness of the El Nino/Southern Oscillation (ENSO) as a predictor of flooding depends on whether or not a more complex phenomenon also measured by sea surface temperatures known as the Interdecadal Pacific Oscillation (IPO) is in a positive or negative phase.
In a series of peer-reviewed papers published in the best international journals since 2003, Professor Franks has shown that when the IPO is negative, as it was from 1946 to 1977, then there is a much greater chance that there will be flooding rains if a La Nina forms.
The IPO started to go negative in 1999, but an El Nino formed in 2001, and seven years of mostly drought followed – sustained by the El Nino conditions.
In February 2009, Professor Franks commented at this weblog that the Australian climate showed signs of entering another wet phase and warned that governments should prepare for a return to a 20-40 year period where La Nina dominates.
Just over a year later, in April 2010, the negative IPO now entrenched, a strong La Nina began to form and flooding rains followed.
Indeed the explanation for the recent devastating flooding is not carbon dioxide, but inadequate infrastructure and warning systems in the face of a combination of La Nina conditions during a negative IPO, a monsoon trough and already saturated catchments.
Better Planning for Extreme Floods Possible: A Note from Stewart Franks
February 27th, 2009