Paleoclimatologist Peter B. deMenocal was on one of the last research vessels to ply the waters off the Horn of Africa before the region was declared off limits to scientists due to the threat posed by Somali pirates—a peril vividly illustrated in this fall’s hit movie, "Captain Phillips."
Fortunately deMenocal was aboard a Dutch-flagged vessel. “If we had been flying the American flag I probably wouldn’t be here today,” says the professor and current chair of the Department of Earth and Environmental Sciences and scientist at Columbia’s Lamont-Doherty Earth Observatory.
After receiving faxes about recent attacks in the area, the crew went on high alert, peering with binoculars across the dark waters off the coast of Somalia. “It was pretty nerve-wracking,” deMenocal recalls. Navigation and interior lights were turned off, the ship’s radio went silent, and plans for what to do if pirates boarded the vessel were reviewed.
During that research mission, three months before the Sept. 11, 2001 attacks, scientists extracted cores of sediment from the deep seabed, providing evidence of profound climate change in North Africa some 5,000 years ago. Wooded grasslands became arid, creating the Sahara Desert—the driest region on Earth—and the population of hunter-gatherers suddenly disappeared.
At about the same time there was a surge in population along the Nile River, which led a few centuries later to the rise of Pharaonic culture in ancient Egypt as people simply moved to find water. “This is a classic example of how a change in climate shaped who we are,” he says. “The land could no longer support the population. They went in search of water.”
His research, part of a Lamont-led initiative called Climate and Life, is challenging prevailing theories that climate in North Africa changed over thousands of years. He concluded that the desertification of the Sahara happened over just 200 years, which he notes is “a wink of time geologically.”
Yet the man-made changes we are experiencing now are occurring even faster. DeMenocal points out, “The current generation, people 30 years old or younger, have lived their whole lives in a world that’s warmer than that of their parents or grandparents or great-grandparents.”
DeMenocal co-authored a paper describing his work in Africa that appeared in last month’s issue of Science magazine. “As we look at how global warming may impact society, it’s useful to look into the past,” he says.
There is evidence of natural climate change going back millions, even billions of years, deMenocal says, and “there’s no shortage of evidence that organisms large and small, from bacteria to mammoths, respond to climate. What is different today is that it’s happening very quickly and populations are dependent upon basic resources that are threatened as climate changes.”
Jessica E. Tierney, lead author of the paper, worked with deMenocal as a post-doctoral fellow at Lamont from 2010 to 2012 and is now a scientist at Woods Hole Oceanographic Institution. By studying changes that happened over thousands of years, she adds, “we get to see a bigger range of what can happen.”
As land becomes arid, for instance, changes in vegetation induce further changes in climate. DeMenocal, who earned his Ph.D. from Columbia in 1991, has done research suggesting that arid conditions in the central Yucatan between 800 and 1000 A.D., along with social upheaval, warfare and disease, contributed to the collapse of Mayan civilization. The Akkadian civilization in what is now northeast Syria collapsed around 2200 B.C. after a centuries-long drought.
He and Tierney are continuing their research on climate change in Africa with a grant from the National Science Foundation, but they will not be able to get new samples off the Somali coast. “We developed a record in a place where it’s impossible to do science anymore,” deMenocal notes.
After a proposal to return to the Gulf of Aden was put on hold because of the pirate risk, deMenocal asked a U.S. Navy admiral if they might request a military escort for protection. “He kind of looked at me and said, ‘Do you have any idea what our day rate is?’” deMenocal recalls with a laugh. The answer was no.
Other parts of Africa are also off limits to deMenocal, who in 2008 won the Lenfest Distinguished Columbia Faculty Award for excellence in teaching and scholarship. “Even on land, in Kenya, there are areas I can’t go to anymore,” he says. “We were shot at the last time I was there.”
—Story by Georgette Jasen
—Video by Columbia News Video