Climate change that strengthens the El Nino weather patterns could endanger food supplies for more than 20 million people in Africa, a new study warns. El Nino is a warming of the water in the tropical Pacific Ocean that is associated with changes in air pressure and the movement of high-level winds that can affect weather worldwide. In the past, El Ninos have occurred every four to seven years, but many climate experts worry that continuing global warming will lead to stronger and more frequent events. A new analysis of 40 years of African crop and livestock records shows a close association between El Ninos and variations in production of corn, sorghum, millet and groundnuts such as peanuts.