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Two Thousand Years of East African Droughts
Reference
Russell, J.M., Verschuren, D. and Eggermont, H. 2007. Spatial complexity of "Little Ice Age" climate in East Africa: sedimentary records from two crater lake basins in western Uganda. The Holocene 17: 183-193.

What was done
The authors conducted lithostratigraphic analyses of sediment cores obtained from two crater lake basins in Western Uganda, Africa - Lake Kitagata (003'S, 2958'E) and Lake Kibengo (004.9'S, 3010.7'E) - which span the past two millennia.

What was learned
Among other things, Russell et al. report that "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 centered on AD ~0 [and] ~1100."

What it means
In discussing what they call the "broader climatic implications" of their findings, the three researchers write that "based on comparison of proxy water-balance records from Lakes Edward (Russell et al., 2003; Russell and Johnson, 2005), Naivasha (Verschuren et al., 2000), Turkana (Halfman et al., 1994), and Tanganyika (Alin and Cohen, 2003), Russell et al. (2003) argued that drought around 2000 years ago (AD ~0) affected 'much, if not all, of equatorial Africa'." Similarly, they say "Verschuren (2004) argued that drought centered on AD 1150 affected much of the region, a hypothesis supported by Russell and Johnson (2005)." Consequently, and in light of the three scientists' similar newer results, they conclude that "droughts at AD ~0 and ~1150" - which roughly mark the midpoints of the Roman and Medieval Warm Periods, respectively - "do appear to have affected much of equatorial Africa."

References
Alin, S.R. and Cohen, A.S. 2003. Lake-level history of Lake Tanganyika, East Africa, for the past 2500 years based on ostracode-inferred water-depth reconstruction. Palaeogeography, Palaeoclimatology, Palaeoecology 199: 31-49.

Halfman, J.D., Johnson, T.C. and Finney, B. 1994. New AMS dates, stratigraphic correlations and decadal climate cycles for the past 4 ka at Lake Turkana, Kenya. Palaeogeography, Palaeoclimatology, Palaeoecology 111: 83-98.

Russell, J.M. and Johnson, T.C. 2005. A high-resolution geochemical record from Lake Edward, Uganda-Congo, and the timing and causes of tropical African drought during the late Holocene. Quaternary Science Reviews 24: 1375-1389.

Russell, J.M., Johnson, T.C., Kelts, K.R., Laerdal, T. and Talbot, M.R. 2003. An 11,000-year lithostratigraphic and paleohydrologic record from Equatorial Africa: Lake Edward, Uganda-Congo. Palaeogeography, Palaeoclimatology, Palaeoecology 193: 25-49.

Verschuren, D. 2004. Decadal and century-scale climate variability in tropical Africa during the past 2,000 years. In: Battarbee, R.W. (Ed.), Past Climate Variability through Europe and Africa. Paleoenvironmental Research Book Series, Elsevier.

Verschuren, D., Laird, K.R. and Cumming, B. 2000. Rainfall and drought in equatorial East Africa during the past 1,100 years. Nature 403: 410-414.

Reviewed 29 August 2007