Who knew that Northern temperatures had the power to influence so much more than our apparel choices? According to a new study by Brown researchers, the weather up north can affect conditions even in southeast Africa.
The study, published in Science Express by Jessica Tierney '04 GS in conjunction with researchers from Brown, the University of Arizona and the Royal Netherlands Institute for Sea Research, counters scientists who believed climate in this part of the world was determined by the low pressure system around the equator known as the inter-tropical convergence zone, according to the study.
Researchers extracted sediment containing tens of thousands of years of climate record from southeast Africa's Lake Tanganyika. To determine rainfall variation, Tierney, a graduate student in the geology department and the study's lead author, studied the composition of leaf wax remains in that sediment using a method that "Brown geology has pioneered," she said. Tierney used the equipment in the Netherlands to perform temperature analyses. The study found that major shifts in temperature and rainfall in the North Atlantic were frequently followed by major shifts in southeast Africa's climate. Because tropical conditions largely determine climate in the rest of the world, it is surprising to find variations in the Northern Hemisphere contributing to tropical climate, Andrew Cohen, professor of geosciences, ecology and evolutionary biology at the University of Arizona and an author of the study.
The study found relatively abrupt climate changes, but these findings do not imply that modern global warming could result from purely natural forces, said Cohen, adding that climate trends are "currently outside natural bounds."
The study does not relate to current conditions but should be viewed as a piece of climatological history that provides context for modern trends, Tierney said. Because of the study's focus on the relationship between two regions and its expansive timescale, it neither supports nor refutes arguments in the debate over global warming, Cohen said. At most, it serves to "put the modern changes in perspective," Cohen said.
Assistant Professor of Geological Sciences James Russell and Associate Professor of Geological Sciences Yongsong Huang also contributed to the study.
