The Southern Oscillation is the term used to describe a phenomenon in which the temperature of the sea and the circulation of atmosphere over the Pacific and Indian Oceans move from one extreme to another in a regular pattern. At one extreme, known as El Niño, the eastern Pacific sea surface warms and air pressure falls, while in the western Pacific the sea surface cools and air pressure rises. Rainfall on the normally arid Peruvian coast increases while the higher pressure and cool seas in the western Pacific bring low rainfall conditions to Papua New Guinea. At the other extreme, known as La Niña, air pressure falls in the western Pacific and warm seas bring high rainfall to Papua New Guinea. The system does not oscillate with perfect regularity and is much of the time somewhere between the extremes. For a number of reasons, some not yet understood and some to do with Papua New Guinea’s complex geography, extreme ENSO events do not all affect Papua New Guinea with similar severity. However El Niño conditions extreme enough to cause drought, such as that experienced in 1997, have probably occurred about once every 100 years for at least the last 6000 years (Haberle 2000), while less severe events have occurred on average around every thirteen years. Papua New Guinea is a high rainfall equatorial country and La Niña impacts are more difficult to identify, although it is possible that they cause longer and more chronic food shortages in areas dependent on sweet potato than the more spectacular but less common El Niño events (Bourke 1988).

The historical record in Papua New Guinea, which is a little over 110 years long in the lowlands and 50 years in the highlands, shows that severe droughts have occurred in 1914–15, 1941–42, 1972, 1982 and 1997. It is also likely, but more difficult to demonstrate, that severe droughts were experienced in 1887 and 1901–02. Documentary reports increase in frequency and geographical coverage over time, but even the early reports suggest widespread disruption to food supplies, fires and famine. In 1901 and 1902, ‘famine’ is reported from Rigo District and Goodenough Island, a ‘complete crop failure’ was reported from Milne Bay and the sago swamps at Cape Nelson burned. In 1914, E.W.P. Chinnery, the government anthropologist, reported that almost the whole population of New Ireland, including those normally dependent on sago, were ‘wandering about in desperation’. He reported ‘destructive bushfires along the whole line of the coast’ and a ‘great loss of life’ (Chinnery 1929, 45). In 1941 ‘abnormal conditions and fires’ were reported from Wau, Bulolo, Madang and Wewak, the New Britain coast was ‘brown from drought or black from the effects of fires’ with ‘smoke everywhere like a thick fog’ and sago swamps burned out on the Sepik River (Pacific Island Monthly November 1941, 6). Food supplies were ‘critical’ in Western Province and the ‘inland mountain districts’ of Papua (Pacific Island Monthly February 1942, 29). Oral accounts from the highlands include frost in Enga followed by mass migrations from the Upper Lai Valley in which ‘many died on the road’ (Dwyer 1952). From Tari in the Southern Highlands comes a description of a two year drought that occurred soon after the visit to Hoiebia by Taylor and Black in 1938 (Gammage 1998, 77) when a bushfire burned right across the central basin, the peaty swamp caught fire and a famine occurred ‘much worse than what happened in 1972’ (Allen et al. 1989, 289).

It is probable that severe ENSO events have been occurring for some thousands of years. The general success of Papua New Guinea food production systems in maintaining the population over that period suggests that these events do not have a long-term negative influence on food production, or that systems are adapted to cope. In pre-colonial times, because severe ENSO events occur only every three or four generations, knowledge of how to cope was recorded in oral accounts. The coming ‘big one’ was used by older people to cajole and threaten young men and women who did not want to work hard in their gardens: ‘Work hard’, they were told, ‘because one day a big famine will happen and you will starve if you don’t have large gardens’.

In a bureaucracy, however, an event which occurs only once every 100 years is not likely to be well remembered. In Papua New Guinea there was almost no administration to record the consequences of the 1901, 1914 or 1941 (in the highlands) events. The loss of experience at independence and concerns with other matters since then, means that in 1997, severe ENSO events were not at the forefront of most peoples’ minds.