By counting down from the sediment surface, the year each couplet was deposited can be determined. Confirmation of the aridity-dependence of the isotopic composition of the lake carbonates, over the last 100 years gives confidence that the analysis of carbonate in older sediments will provide information on climatic patterns in Ethiopia before instrumental records began. Lakes and snails Lake Tilo lies in a semi-arid savanna region of the Ethiopian Rift Valley. The lake was full and overflowing during this period, and rainfall was considerably higher than today. NERC copyright all rights reserved.
Snails are the latest recruits to palaeoclimatology.
The snail shells record finer detail than the lake sediments, and reveal the times of the year when monsoon rains entered the lake. For example snail shells from 9000 years ago tell us that the monsoon wet season occurred over a greater proportion of the year than at present. Subsistence economies of the Developing World are particularly susceptible to the ravages of extreme climate. Floods and droughts and the terrible suffering they bring have been graphically illustrated in the last twenty years, for example in Ethiopia, Bangladesh and Sudan. By understanding the past climate variation, in particular by investigating annual and interannual variation, we hope to be able to improve climate model simulations.