CHAOS CONTROL OF EL NINO in a sophisticated computer simulation has been achieved by an Israel-US team. El Nino is a prolonged warming of the Pacific Ocean surface near the equator every 3 to 6 years, bringing about storms and widespread climate effects. Recent theories suggest that El Nino is chaotic: its behavior is unpredictable but sensitive to initial conditions of such variables as temperature, atmospheric pressure and winds. A Weizmann-Columbia group (Eli Tziperman, eli@beach.weizmann.ac.il; Stephen Zebiak, 914-365-8597) altered the magnitude of ocean waves reflecting from the western boundary of the Pacific Ocean, in a realistic El Nino prediction model developed at Lamont-Doherty Earth Observatory in New York. When they did this, the model produced an El Nino about every 4 years with periodic and perfectly predictable cycles of temperature, winds, and ocean currents. Although the researchers do not propose to apply chaos control directly to El Nino, they believe it may help them better understand the crucial factors governing El Nino's behavior. In addition, the research required improvements in existing chaos control methods, as the El Nino model has many more variables and parameters than previously controlled chaotic systems. (Tziperman et al., upcoming article in Physical Review Letters.)