El Niño refers to the phenomenon that occurs when warming waters in the tropical Pacific build up around Christmastime. It is a fairly regular occurrence (every two to seven years, but usually every three to four years, and with powerful ones every 10 to 15 years), and because it happens around Christmas, Spanish-speaking people called it El Niño after the Christ child. Meteorologists often refer to it as the ENSO, which is short for El Niño Southern Oscillation. The term Southern Oscillation was coined by Sir Gilbert Thomas Walker (1868–1958), a British statistician and physicist who was studying the pattern of Indian monsoon seasons. The El Niño effect influences weather not only along the Pacific coasts of the Americas, but also worldwide. The consequences range from colder-than-normal temperatures in the central and eastern United States to strong storms in Africa, Australia, and the coast of California, flooding in Europe, and declines in fish populations in South America. Climatologists increasingly believe that strong El Niños increase droughts in Africa and may be accelerating desertification there. A moderate El Niño effect was in action during the years 2006 through 2008.