Climatic variability related to El Niño in Ecuador − a historical background

Abstract. This paper reports on an investigation into the chronology of El Niño/Southern Oscillation (ENSO) events, during the period from the arrival of conquistadores in Ecuador in 1532 until the year 1900. A number of probable El Niño events and drought years can be dated from anecdotal reports of significant rainfall and drought in the equatorial region.

The evidence of ENSO has been documented from early reports in the South America archives. A large number of books and articles have been reviewing from the Ecuadorian archives to obtain information on El Niño events that have occurred over the past centuries. This information is based on evidence obtained from the equatorial region, where strong and very strong El Niño events clearly separate the northern part of the Ecuadorian coast from the southern region, the normally rainy season specially from west-central to the south coast of Ecuador, as well as the drought years, reported in this region which is climatologically and oceanographically different from the moist Northern coast of Ecuador. Given the normal occurrence of rains in the southern coast of Ecuador, it is reasonable to expect that at least some of the major rainy seasons would be recorded in local chronicles and publications. This information has been compared with reports obtained from Peru.

Relative strengths of events are based on such considerations as wind and current effects on travel times of ancient sailing ships, degree of physical damage and destruction, amounts of rainfall and flooding, human disease epidemic, mass mortality of endemic marine organism, rises in sea temperatures and sea levels, effects on coastal fisheries.

This paper is the first survey of the historical sources concerned the rainfall and drought in Ecuador. In the course of this investigation we also noted some extended periods of time, near decadal or longer over the past records, when the amount and/or strength of El Niño and its resulting effects appeared to represent significant long-term climate changes.