RECENT TEMPERATURE-VARIATIONS IN SOUTHERN SOUTH-AMERICA

Results from a critical appraisal of surface mean air temperature in C hile and Argentina and extreme air temperature in Chile during the pre sent century are presented. Observations were homogenized to produce a set of time series as reliable as possible. Linear trends computed fo r the period 1933-1992 resulted in warming rates from 1.3 to 2.0 degre es C 100 years(-1); during the last three decades warming rates are tw ice as large. The generalized warming is not present around 41 degrees S, where a cooling period from the 1950s to the 1970s prevails. Both positive and negative trends are due mostly to changes in minimum temp eratures. The influence of El Nino-Southern Oscillation on surface tem perature along the Pacific South American coast from 18 degrees S to 5 3 degrees S was estimated and found to decrease southward. When its ef fect is extracted, warming trends become more uniform through time. In particular, the Southern Oscillation Index change around 1976 is felt in minimum temperatures at almost all stations, starting a period wit h higher values along the Chilean Pacific coast. Trend corrections for autocorrelation in the series introduce only small local changes.