He taught at Euphrates College, Turkey (1897–1901); accompanied the Pumpelly (1903) and Barrett (1905–1906) expeditions to central Asia; and wrote of his Asian experiences in Explorations in Turkestan (1905) and The Pulse of Asia (1907). He taught geography at Yale (1907–1915) and from 1917 was a research associate there, devoting his time chiefly to climatic and anthropogeographic studies. The Climatic Factor (1914), Civilization and Climate (1915, rev. ed. 1924), and, with S. S. Visher, Climatic Changes (1922) were among his works. He also wrote Principles of Human Geography (with S. W. Cushing, 5th ed. 1940) and Mainsprings of Civilization (1945). He was on the original standing committee of the Foundation for the Study of Cycles from 1941.