East Africa's drought is the worst in sixty years. Scientists say the dry conditions in the Horn of Africa are at least partly the result of an event half a world away. The event is called La Niña, which means "little girl" in Spanish. A La Niña begins when waters become cooler than normal in the eastern Pacific Ocean near the equator. Changes in wind currents can then affect weather around the world. A related event, called an El Niño, happens when the waters become unusually warm. La Niñas and El Niños happen about every three to five years. The latest La Niña began in July of last year and ended in May. The conditions can last for up to two years.Wassila Thiaw studies Africa for the Climate Prediction Center at the National Weather Service in the United States. With a La Niña, Mr. Thiaw says the easterly winds that are supposed to bring moisture into East Africa are reduced. And when that happens, rainfall is reduced.Starting late last year, rains that were supposed to fall over Somalia, southern Ethiopia and northern Kenya failed. That part of the Horn of Africa has a second rainy season during March, April and May. Mr. Thiaw says that one failed, too, but "probably mostly due to the atmospheric conditions that prevailed at that time." He says La Niña conditions might begin again by the end of this year. And if that happens, he says, then the October-through-December rainy season could again be dryer than normal. Climate researcher Simon Mason at Columbia University in New York says East Africa has been getting drier over about the last ten years. Mr. Mason says this is at least partly the result of global warming. Rising temperatures in the Indian Ocean create conditions that pull moisture away from East Africa.Claudia Ringler at the International Food Policy Research Institute also points to another issue. She said much of the land in the drought-affected areas is not very productive even in good times. "It will not get any better. Even if we have a bit more rainfall, the general potential for more food production is not expected to improve dramatically in the region." In the United States, the latest La Niña pushed moisture away from the south, causing severe droughts. Texas has suffered billions of dollars in agricultural losses. Changes in the winds pushed the rain toward northern states, causing floods.

For VOA Special English, I'm Carolyn Presutti. You can learn English and stay informed every day at voaspecialenglish.com.