NEW YORK • In rural villages in Africa and Asia, and in urban neighbourhoods in South America, millions of lives have been disrupted by weather linked to the strongest El Nino in a generation.
In some parts of the world, the problem has been not enough rain; in others, too much. Downpours were so bad in Paraguay's capital, Asuncion, that shantytowns sprouted along city streets, filled with families displaced by floods.
But farmers in India had the opposite problem: Reduced monsoon rains forced them off the land and into day-labour jobs.
The World Health Organisation has estimated that El Nino-related weather is putting 60 million people at increased risk of malnutrition, water- and mosquito-borne diseases, and other illnesses.
Scientists began reporting early signs of El Nino conditions early last year. By mid-year, the World Meteorological Organisation declared that El Nino was in full swing and that it was on track to be the strongest such event since 1997-98.
An El Nino occurs, on average, every two to seven years, when warm Pacific water shifts eastwards, creating an immense warm zone in the central and eastern Pacific. This adds heat and moisture to the air, which condenses high in the atmosphere, releasing energy that affects the high-altitude winds known as jet streams that circle the planet. The warmer the ocean, the more energy that can potentially be released.
"It's like waving a paddle back and forth in the stream and generating planetary-scale atmospheric waves," said senior scientist Michael McPhaden at the National Oceanic and Atmospheric Administration.
That leads to patterns of precipitation, or lack of it, that can pop up in far-flung regions at different times - heavy rains in south-central South America from September to January, increased dryness in Central America for much of the year and a reduced summer monsoon in India, among other effects.
Because these patterns often recur in different El Nino years, the effects can be predictable. Nonetheless, they can still test the ability of governments and aid agencies to respond.
NEW YORK TIMES