EL-NINO, VOLCANISM, AND GLOBAL CLIMATE

The June 1991 eruption of Mt. Pinatubo in the Philippines produced one of the greatest volcanic aerosols in the last hundred years. The esti mated net decrease of radiation may have peaked at 10% in the tropics. What was the impact of the Pinatubo aerosol on regional and global cl imate? Besides the expected net cooling of the average global surface temperature, correlation studies indicate that other types of climate anomalies may also be expected These include the appearance of an El N ino event, decreased Indian monsoon rainfall, fewer tropical storms in the north Atlantic Ocean in 1991-1993, and normal to above normal win ter rainfall in California in 1991/92, all of which were observed. A p roposed physical mechanism for the almost-simultaneous occurrence of t his constellation of climate anomalies is presented. The results of co rrelation studies between low-latitude volcanic aerosols and the El Ni no/Southern Oscillation are presented in some detail as one example. T he correlation between Indian monsoon rainfall and tropical storms in the north Atlantic Ocean is also shown and is updated for the most rec ent 5 years.