Changing Planet

Pacific cooling may have caused epic droughts in Europe and North America

Did the Anasazi people abandon their cliff dwellings in North America because of the same weather event that caused great famine in Europe 700 years ago?

A new study has found a connection between La Niña-like sea surface temperatures in the central Pacific and droughts in western Europe and in what later became the southwestern United States and Mexico, the University of Miami (UM) said today.

The research is published in a recent issue of Geophysical Research Letters.

“We’ve known for some time the connection between El Niño and La Niña and the weather conditions in North America and Europe,” said Robert Burgman, a climate scientist at UM’s Rosenstiel School of Marine & Atmospheric Science. “La Niña-like conditions, such as those we found, can cause persistent drought, and as we know warm conditions cause increased precipitation.”

Using cores of fossil coral from the Palmyra Atoll in the central Pacific Ocean, Burgman and a team used reconstructed sea surface temperatures from the period 1320 to 1462 to simulate medieval climate conditions with a state-of-the-art climate model, UM said in a news statement.

“When the differences between medieval and modern climate simulations were compared with paleo-records like tree-rings and sediment cores from around the globe, the authors found remarkable agreement.

“During the 142-year study period, the sea surface temperature dropped only one-tenth of one degree, but it was enough to cause arid conditions in North America and Europe.

Anasazi-cliff-dwelling-photo.jpg

This cliff palace, in Mesa Verde National Park,  once sheltered hundreds of Anasazi people.

NGS stock photo by Willard Culver

The Anastazi people–who lived in dramatic cliff dwellings near what later became known as the “Four Corners” area at the intersection of the state of Utah, Colorado, New Mexico, and Arizona—left their settlements at Mesa Verde and other locations some 600 years ago without explanation. A prolonged drought is thought to be one of the contributing factors to their departure.

“In Europe, the study period was preceded by three years of torrential rains, which led to the Great Famine from 1315 to 1320, and marked the transition from the Medieval Warm Period to the Little Ice Age, which began in the mid 1500s. During that time, extreme weather conditions were thought to be responsible for continued localized crop failures and famines throughout Europe during the remainder of the 14th Century,” UM said

“The marriage of complex climate models with paleo-records of sea surface temperature and other climate variables provide valuable insight to climate scientists who wish to understand climate variability and change before the instrumental record,” said Burgman.

Warning that the Palmyra Atoll data only represents one data point, Burgman emphasized that he would like to test his thesis with data from other oceans. “If we can fill in the gaps with data from corals and other records from the Atlantic, Pacific, and Indian oceans, we’ll have a better idea of what has happened to the global climate over time,” he said.

Posted by David Braun 

Forty years in U.S., UK, and South African media gives David Braun global perspective and experience across multiple storytelling platforms. His coverage of science, nature, politics, and technology has been published/broadcast by the BBC, CNN, NPR, AP, UPI, National Geographic, TechWeb, De Telegraaf, Travel World, and Argus South African Newspapers. He has published two books and won several journalism awards. He has 120,000 followers on social media. David Braun edits the National Geographic Society blog, hosting a global discussion on issues resonating with the Society's mission and initiatives. He also directs the Society side of the Fulbright-National Geographic Digital Storytelling Fellowship, awarded to Americans seeking the opportunity to spend nine months abroad, engaging local communities and sharing stories from the field with a global audience. Follow David on Facebook  Twitter  LinkedIn

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