In
1899, the Indian monsoon failed, leading
to drought and famine in India. This led Gilbert Walker, the head
of the Indian Meteorological Service,
to search for a way to predict
the Indian monsoon. By the early
20th century, he had identified a
peculiar see-saw relationship between
pressure over the maritime continent
and India and the Pacific near
South America. When pressure is
high over the eastern Pacific, it is low
over the maritime continent, and vice
versa. He called this relationship
the Southern
Oscillation.