The Holocene Climate Optimum was a warm period during roughly the interval 9,000 to 5,000 years BP. It has also been known by many other names, such as Altithermal, Climatic Optimum, Holocene Megathermal, Holocene Optimum, Holocene Thermal Maximum, Hypsithermal, and Mid-Holocene Warm Period.
Of or belonging to a time during which the climate is relatively warm —often used of a part of postglacial time