ScienceDaily: A new study of lake sediments in Ghana suggests that severe droughts lasting several decades, even centuries, were the norm in West Africa over the past 3,000 years. The earlier dry spells dwarfed the well-documented drought that plagued West Africa in the late-20th century, and as the planet warms, the study’s authors believe the region’s rainfall patterns will have an even greater impact. The team of geoscientists and climate scientists, led by Jonathan Overpeck of the …