More Little Ice Age Droughts In Africa
By Paul Homewood
Further to my post last week on African Droughts in the LIA, Jimbo sent links to a couple of other papers show similarly severe events, both then and earlier.
1) Little Ice Age drought in equatorial Africa: Intertropical Convergence Zone migrations and El Niño–Southern Oscillation variability.
By JM Russell & TC Johnson, 2006.
High-resolution analyses of the Mg concentration in authigenic calcite in five cores from Lake Edward provide a water balance history of central equatorial Africa spanning the past 1400 yr. A high ratio of Mg to Ca (%Mg) indicates strong droughts in central Africa during the Little Ice Age (A.D. 1400–1750), in contrast to records from Lake Naivasha, Kenya, which suggest a wet Little Ice Age. This spatial pattern in Africa likely arose due to coupled changes in the high latitudes, the position of the Intertropical Convergence Zone, and the El Niño–Southern Oscillation (ENSO) system. Our results further suggest that the patterns and variability of twentieth-century rainfall in central Africa have been unusually conducive to human welfare in the context of the past 1400 yr.
2) Spatial complexity of ‘Little Ice Age’ climate in East Africa: sedimentary records from two crater lake basins in western Uganda
By J Russell et al, 2007.
Lithostratigraphic analyses of the sedimentary record from two contrasting crater lake basins in western Uganda, Africa, provide evidence for three major century-scale arid intervals during the last 2000 years. Variations in sedimentation and salt mineralogy of hypersaline Lake Kitagata, and a succession of fine-grained lake sediments and peat in the freshwater Lake Kibengo, suggest century-scale droughts centred on AD 0, ~1100, ~1550 and 1750. These results broadly support data from nearby Lake Edward on the timing of drought in western Uganda, but contrast with lake sediment records from eastern equatorial Africa. In particular, our results suggest regional variability of East African climate during the main phase of the ‘Little Ice Age’ (AD ~1500 to 1800), with westernmost East Africa experiencing drought while areas farther east were wet. This spatial pattern highlights the strongly regional nature of century-scale climate changes over the African continent, and holds implications for the mechanisms governing African rainfall during the ‘Little Ice Age’.
These papers challenge the naive assumption that a warmer global climate since the Little Ice Age has made droughts in Africa worse, or that large scale changes in rainfall patterns have not happened in the past.
But the most interesting comment is:
Our results further suggest that the patterns and variability of twentieth-century rainfall in central Africa have been unusually conducive to human welfare in the context of the past 1400 yr.