Medieval Warm Period

The Medieval Warm Period (MWP), Medieval Climate Optimum, or Medieval Climatic Anomaly was a time of warm climate in the North Atlantic region, that may also have been related to other climate events around the world during that time, including in China and other countries, lasting from about AD 950 to 1250. It was followed by a cooler period in the North Atlantic termed the Little Ice Age. Some refer to the event as the Medieval Climatic Anomaly as this term emphasizes that effects other than temperature were important.

Despite substantial uncertainties, especially for the period prior to 1600 when data are scarce, the warmest period of the last 2,000 years prior to the 20th century very likely occurred between 950 and 1100, but temperatures were probably between 0.1 °C and 0.2 °C below the 1961 to 1990 mean and significantly below the level shown by instrumental data after 1980. The heterogeneous nature of climate during the Medieval Warm Period is illustrated by the wide spread of values exhibited by the individual records. Warmth in some regions appears to have matched or exceeded recent levels of warmth in these regions, but globally the Medieval Warm Period was cooler than recent global temperatures.