Sir Gilbert makes the connection

The Walker circulation was named after the man who first predicted that weather is a global phenomenon -- Sir Gilbert Walker.

At the turn of this century, scientists still believed this strange phenomenon occurred independently of any other weather patterns. During the 1920s, while scientists in South America were busy documenting the local effects of El Niño, Sir Gilbert Walker was on assignment in India, studying monsoons. A British scientist, Walker, who was the head of the Indian Meteorological Service, had been asked in 1904 to try to figure out how to predict the vagaries of India's monsoons after an 1899 famine that was caused by monsoon failure.

As he sorted through world weather records, he recognized some patterns of rainfall in South America and associated them with changes in ocean temperatures. He also found a connection between barometer readings at stations on the eastern and western sides of the Pacific (Tahiti and Darwin, Australia, to be exact). He noticed that when pressure rises in the east, it usually falls in the west, and vice versa. He coined the term Southern Oscillation to dramatize the ups and downs in this east-west seesaw effect. He also realized that Asian monsoon seasons under certain barometric conditions were often linked to drought in Australia, Indonesia, India, and parts of Africa and mild winters in western Canada.

As the first person to claim there was a connection between monsoons in India and unusually mild winters in Canada, naturally he took some grief. In a modern rendition of "the world is flat" scenario, he was publicly criticized for suggesting that climatic conditions over such widely separated regions of the globe could be linked. Walker conceded that he couldn't prove his theory, but predicted that whatever was causing the connection in weather patterns would become clear once wind patterns above ground level, which were not routinely being observed at that time, were thrown into the equation. He was right.