El Niño and Global Warming
The El Niño Southern Oscillation is, after the march of the seasons, the largest periodic weather pattern on Earth. El Niño, the periodic warming of the Eastern Pacific, affects weather over half the planet, causing droughts in Australia and the Phillipines; above average rains in much of North and South America; and moving the position of the jet stream, which changes storm tracks over much of North America.
The basic governor of the ENSO system is the heat content of the Pacific Ocean. Warm water accumu- lates in the Western Pacific for three to five years, then flows back east- ward for about three months. This back and forth movement of a large body of water, like a pendulum, gives rise to its name, the Southern Oscilla- tion. We spoke with Michael McPhaden about the history of ENSO, current research, and about how it interacts with other environmental changes.