altithermal period
From Glossary of Meteorology
The period from about 5000–2500 B.C., proposed by Ernst V. Antevs (1952), during which the summer temperature of western North America was 1°–2°C warmer than today and during which the lakes of the American Great Basin dried.
Antevs, E. 1952. Cenozoic climates of the Great Basin. Sonderdruck aus der Geologischen Rundschau. Bd. 40, Heft 1, . 94–108.