What was done
The authors describe climatic and hydrologic conditions in equatorial East Africa from the late 1700s to close to the present, based on histories of the levels of ten major African lakes.  They also use a water balance model to infer changes in rainfall associated with the different conditions, concentrating most heavily on Lake Victoria.

What was learned
The data were indicative of "two starkly contrasting climatic episodes."  The first, which began sometime prior to 1800 and was characteristic of Little Ice Age conditions, was one of "drought and desiccation throughout Africa."  This arid episode, which was most extreme during the 1820s and 30s, was accompanied by extremely low lake levels.  As the authors describe it, "Lake Naivash was reduced to a puddle ... Lake Chad was desiccated ... Lake Malawi was so low that local inhabitants traversed dry land where a deep lake now resides ... Lake Rukwa [was] completely desiccated ... Lake Chilwa, at its southern end, was very low and nearby Lake Chiuta almost dried up."  Throughout this unfortunate period, "intense droughts were ubiquitous."  Some, in fact, were "long and severe enough to force the migration of peoples and create warfare among various tribes."

As the Little Ice Age's grip on the world began to loosen in the mid to latter part of the 1800s, however, things began to tend towards the better for most of the continent.  The authors report that "semi-arid regions of Mauritania and Mali experienced agricultural prosperity and abundant harvests; floods of the Niger and Senegal Rivers were continually high; and wheat was grown in and exported from the Niger Bend region."  Across the east-west extent of the northern Sahel, in fact, maps and geographical reports described "forests."

As the nineteenth century came to an end and the twentieth century began, there was a slight lowering of lake levels, but nothing like what had occurred a century earlier.  And then, in the latter half of the twentieth century, things once again began to pick up for the Africans, with the levels of some of the lakes actually rivaling the high-stands characteristic of the years of transition to the Modern Warm Period.

What it means
Even in Africa, global warming is better than global cooling.