After reviewing more than 200 climate studies, researchers have determined that, contrary to what many scientists thought, the 20th century is not the warmest in the past millennium.

Researchers at the Harvard-Smithsonian Center for Astrophysics have confirmed that the Medieval Warm Period of 800 to 1330 AD occurred, as did the Little Ice Age of 1300 to 1850 AD.

For a long time, researchers only had anecdotal evidence for the existence of these climate extremes, says Saliee Baliunas, a Smithsonian astronomer and a coauthor of the study.

“For example, the Vikings established colonies in Greenland at the beginning of the second millennium that died out several hundred years later when the climate turned colder,” says Baliunas. “And in England, vineyards had flourished during the medieval warmth. Now, we have an accumulation of objective data to back up these cultural indicators.”

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