Verschuren D, Laird K R, Cumming B F
Limnological Research Center, University of Minnesota, Minneapolis 55455, USA.
Nature. 2000 Jan 27;403(6768):410-4. doi: 10.1038/35000179.
Knowledge of natural long-term rainfall variability is essential for water-resource and land-use management in sub-humid regions of the world. In tropical Africa, data relevant to determining this variability are scarce because of the lack of long instrumental climate records and the limited potential of standard high-resolution proxy records such as tree rings and ice cores. Here we present a decade-scale reconstruction of rainfall and drought in equatorial east Africa over the past 1,100 years, based on lake-level and salinity fluctuations of Lake Naivasha (Kenya) inferred from three different palaeolimnological proxies: sediment stratigraphy and the species compositions of fossil diatom and midge assemblages. Our data indicate that, over the past millennium, equatorial east Africa has alternated between contrasting climate conditions, with significantly drier climate than today during the 'Medieval Warm Period' (approximately AD 1000-1270) and a relatively wet climate during the 'Little Ice Age' (approximately AD 1270-1850) which was interrupted by three prolonged dry episodes. We also find strong chronological links between the reconstructed history of natural long-term rainfall variation and the pre-colonial cultural history of east Africa, highlighting the importance of a detailed knowledge of natural long-term rainfall fluctuations for sustainable socio-economic development.
了解自然长期降雨变化对于世界半湿润地区的水资源和土地利用管理至关重要。在热带非洲，由于缺乏长期的仪器气候记录以及树木年轮和冰芯等标准高分辨率代用记录的潜力有限，与确定这种变化相关的数据稀缺。在此，我们基于从肯尼亚奈瓦沙湖的湖平面和盐度波动推断出的三个不同古湖沼学代用指标：沉积物地层学以及化石硅藻和蠓类组合的物种组成，呈现了过去1100年赤道东非降雨和干旱的十年尺度重建。我们的数据表明，在过去一千年中，赤道东非在对比鲜明的气候条件之间交替，在“中世纪暖期”（约公元1000 - 1270年）气候比现在明显干燥，而在“小冰期”（约公元1270 - 1850年）气候相对湿润，期间被三次长期干旱事件打断。我们还发现自然长期降雨变化的重建历史与东非殖民前文化历史之间存在紧密时间联系，凸显了详细了解自然长期降雨波动对可持续社会经济发展的重要性。
