Jennifer Marohasy’s article in the Weekend Australian newspaper (23/8/2008) is yet another installment in the ongoing saga of Australian non-greenhouse theorists (‘sceptics’) attempting to discredit, at least in the eyes of the general public, the conclusions of Australian climate science. But one wonders why Institute for Public Affairs supporters choose to give their imprimatur to such risky advice.
In contrast to Dr Marohasy’s piece, a robust discussion of rainfall trends their relationship to the anthropogenically driven component of global warming (AGW) must involve some aspect of risk and uncertainty. Such uncertainty can be amplified (either way) to suit supporters or detractors of the evidence underpinning global warming – and hence influence actions required to avoid dangerous climate change. However a fair and robust case for risks involved in the AGW case should be put explicitly, instead of simply pretending that such detailed advice did not exist.
The basic problem with the Australian temperature and rainfall graphics used in the Marohasy article is the issue of averages and the practice of ‘smearing’ the statistics. For instance, if we examined the time series of Australian rainfall, the immediate conclusion might be that there is no trend, or even a slight upward trend, over the entire time span. However, this continental-wide data averages over both a wetter north-west and a drier eastern, south-eastern and south-western Australia. Such an average can blur very significant and environmentally important regional trends.
Indeed if things are “so average” and of little concern, why has the Australian media been full of drought stories for the last 5 years? So, on to the basics…