HISTORICAL ENSO TELECONNECTIONS IN THE EASTERN HEMISPHERE PETER WHETTON CSIRO Division of Atmospheric Research, P.B. No. 1, Mordialloc, Vic 3195, Australia and IAN RUTHERFURD* Department of Geography and Environmental Science, Monash University, Clayton, Vic 3178, Australia Abstract. Examination of instrumental data collected over the last one hun- dred years or so shows that rainfall fluctuations in various parts of the eastern hemisphere are associated with the E1 Nifio-Southern Oscillation (ENSO) phe- nomenon. Using proxy rainfall data-sets from Indonesia, Africa, North China; and a chronology of droughts from India, we investigate the occurrence of ENSO- related floods and droughts over the last five hundred years. The aim of this work is to examine the stability of the pattern of ENSO teleconnections over this longer period, noting any changes in ENSO behaviour which may be relevant in esti- mating its future behaviour, such as its response to climate change due to the enhanced greenhouse effect. Comparisons of the various data sets with each other and with E1Nifio chronology from South America, showed statistically significant evidence of teleconnections characteristic of ENSO back to around 1750. Prior to that time, relationships characteristic of ENSO were weak or absent. The disappearance of the ENSO signal in the early period is considered to be most likely due to the poorer quality of the data at that time. From the 18th Century onwards, chronologies of ENSO and anti-ENSO events are given and compared with similar chronologies in the literature. 1. Introduction Over much of the middle to lower latitudes of the globe, E1 Nifio-Southem Oscil- lation events are a most important source of year to year variability in climate. These episodes involve large-scale ocean-atmosphere interactions. The Southern Oscillation component represents a tendency for atmospheric surface pressure to be below normal throughout the central and south Pacific at the same time that it is above normal across Australia, South-East Asia and the Indian Ocean, and vice versa. During the phase where the pressure is low in the Pacific, warm water replaces the usually cool surface waters of the central and eastern equatorial Pacif- ic - an event known as 'El Nifio' (although originally 'El Nifio' referred to only the warming off Peru). Together, the anomalies in the atmosphere and ocean are known as an 'El Nifio-Southern Oscillation' (ENSO) events. During the opposite phase, an 'anti-ENSO event', surface waters in the eastern Pacific are colder than * Now at: Department of Civil Engineering, Monash University, Clayton, Vic 3178, Australia. Climatic Change 28: 221-253, 1994. (~ 1994 Kluwer Academic Publishers. Printed in the Netherlands.