The recent decline in Horn of Africa rainfall during the March–May “long rains” season has
fomented drought and famine, threatening food security in an already vulnerable region.
Some attribute this decline to anthropogenic forcing, whereas others maintain that it is a
feature of internal climate variability. We show that the rate of drying in the Horn of Africa
during the 20th century is unusual in the context of the last 2000 years, is synchronous with
recent global and regional warming, and therefore may have an anthropogenic component …