El Niño–Southern Oscillation
El Niño–Southern Oscillation (ENSO) events have a profound impact across a wide global band and are now recognised as the main source of Australia's infamous droughts. Tasmania is the coolest and wettest of the Australian states and the absolute reduction in precipitation is seldom as great as in the vulnerable areas of the mainland, but it has been severely impacted upon by El Niños.
Tasmanian annual average rainfall is highest in the mountainous south-west and in essence reduces further towards the north-eastern corner of the island. El Niños essentially replicate this pattern, with the north-eastern third of the state having suffered most regularly and severely, while the impact has been much less towards the south-west. However, the chronology (frequency and length), spatial distribution and severity of El Niños vary considerably, even within limited regions like Tasmania. The 1914 El Niño was the driest on record (closely followed by 1965–67 and 1982–83) when the impact was felt severely across the whole northern half of the state. By contrast, 1972 affected little more than a narrow strip on the east coast and 1997 a narrow strip along the northern coast.
Because Tasmania is generally so moist, it is not easy to find references to drought or El Niño in its histories. Nevertheless, reduced rainfall has historically threatened water supplies, grazing land and crops. More dangerous has been the desiccation of forest vegetation and it is far easier to find references to bushfires. The normally high rainfall produces dense growth which becomes highly combustible during a 'drought'. The El Niño which has impacted most on the psyche of the state was that in 1965–67 which led to disastrous bushfires around Hobart in 1967. (See also Climate.)
Further reading: R Allan et al, El Niño Southern Oscillation and climatic variability, Melbourne, 1996; N Nicholls, 'Historical El Niño/Southern Oscillation variability in the Australasian region', in H Diaz & V Margraf (eds), El Niño, Cambridge, 1992.