Dr David Jones, the head of climate analysis at the Bureau of Meteorology, recently attributed a decline in Melbourne’s rainfall to global warming. Amongst various comments, he claimed in The Age that the autumn drying trend could be linked to either human-induced climate change through greenhouse gases or changes in the ozone layer over Antarctica.
Ockham’s Razor, the principle proposed by William of Ockham in the fourteenth century: “Pluralitas non est ponenda sine neccesitate”, which translates as “entities should not be multiplied unnecessarily” would require that Dr Jones choose one or the other theory, greenhouse gases or depletion of the ozone layer, as an explanation for the decline in rainfall.
But does either theory really represents much more than speculation?
Indeed lead authors of the Intergovernmental Panel on Climate Change (IPCC) acknowledged just after the release of their last big report that until major oscillations in the Earth System, including El Nino-Southern Oscillation, Pacific Decadal Oscillation, North Atlantic Oscillation and Atlantic Multidecadal Oscillation, are better understood regional climate, and in particular regional rainfall, is a difficult problem.
Furthermore, there are perhaps other simpler explanations for the recent decline in rainfall.
Indeed Dr Jones recently confirmed that his comments in The Age were based on data from just one weather station: a site in Melbourne’s central business district.
This brings us back to Part 1 of this series in which Bill Kininmonth, a meteorologist formerly with the Bureau, made comment that “the rain gauge in Melbourne’s central business district is now sheltered from the rain bearing winds of the southwest”.