How did middle Holocene global temperatures compare with late 20th-century temperatures?

During the middle Holocene Epoch—approximately 5,000 to 7,000 years ago—global climate conditions were characterized by significant regional and seasonal variability, a period often referred to as the Mid-Holocene Climatic Optimum.1

While some regions and seasons experienced temperatures that were warmer than those of today, these were balanced by cooler conditions elsewhere, such as cooler winters in the Northern Hemisphere and cooler year-round temperatures in the tropics. Because of this regional heterogeneity, the "thermal maximum" did not occur as a single, uniform global event.12

When considering the global mean, recent theoretical climate model studies indicate that average temperatures during the middle Holocene were likely 0.2–0.3 °C (0.4–0.5 °F) colder than the average conditions observed during the late 20th century.1