Charles Warren Thornthwaite (March 7, 1899 – June 11, 1963) was an American geographer and climatologist.

He moved away from geography to climatology, but recent scholarship suggests he was nonetheless ahead of his time in his thesis project and that many of the techniques he used would later be standard procedures.

[6][7] In 1931 Thornthwaite published “The Climates of North America: According to a New Classification”,[8] which launched his career as a climatologist and married the science of climatology with that of geography.

Thornthwaite learned about the Köppen while at UC Berkeley and while in Oklahoma he began to study the flaws of the classification.

Thornthwaite created the P-E index to measure precipitation and evaporation, which he did from April to September in twenty-one stations in the United States.

Included in his output from this period was the USDA technical bulletin, written with Benjamin Holzman, Measurement of Evaporation from Land and Water Surfaces.

[9] Leaving government in 1946, Thornthwaite opened the Laboratory of Climatology in Seabrook, New Jersey, which he operated until his death in 1963.

It incorporates evapotranspiration, temperature and precipitation information and is widely used in studying animal species diversity and potential impacts of climate change.

The fund awards annual merit scholarships to students in meteorology and earth science at Central Michigan University.