The origin of the Tropical Oceans–Global Atmosphere (TOGA) Program was closely related to the response of global atmospheric circulation to sea surface temperature variations in the tropical Pacific Ocean, which is evident by the El Niño phenomenon. During the two decades before the 1985 start of TOGA, advancements in scientific understanding of the tropical ocean and global atmosphere and advancements in technology provided strong foundations for TOGA. By the early 1980s, research had demonstrated a strong linkage between tropical SST variations and global atmospheric circulation, and discussions of an international ocean–atmosphere program had begun. Probably the single most important event leading to the creation of TOGA was the unannounced arrival in 1982 of the largest El Niño in a century.