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PUBLICATION HIGHLIGHT: Reconciling Theories for Human and Natural Attribution of Recent East Africa Drying

Wilted wheat in Ethiopia. Photo credit: Getachew Abate Mussa, Famine Early Warning Systems Network
Wilted wheat in Ethiopia. Photo credit: Getachew Abate Mussa, Famine Early Warning Systems Network

APRIL 11, 2017—The spring (March–May) rains over the Greater Horn of Africa are critical to the region’s agriculture and water resources. During 1979–2013, many spring droughts produced a marked drying trend, which played a role in humanitarian disasters. Two theories for this drying were later proposed: one that invokes a primarily human cause, and the other a primarily natural cause.

In a study published in the March 2017 issue of the Journal of Climate, NOAA and CIRES researchers from the ESRL Physical Sciences Division reconcile these two theories for the observed East Africa drying trends during spring 1979–2013. Model simulations indicate that observed sea surface temperature variations contributed significantly to the East Africa drying trend during the spring periods from 1979–2013. The model simulations suggest that anthropogenic forcing alone did not contribute significantly to East Africa drying. However, the same model simulations demonstrate that the co-action of anthropogenic forcing and natural ENSO-like decadal variability can significantly enhance these March–May East Africa drying trends relative to when the natural ocean variability acts alone. A human-induced change via its interplay with an extreme articulation of natural variability may thus have been key to Africa drying.

Authors of Reconciling Theories for Human and Natural Attribution of Recent East Africa Drying are Andrew Hoell, Martin Hoerling, Jon Eischeid, Xiao-Wei Quan, and Brant Liebmann of the ESRL Physical Sciences Division.