Last millennium climate reconstruction in Ethiopia using multiple stalagmite parameters

埃塞俄比亚高地是一个典型的对降雨敏感的地区，由于对历史模式、其更广泛的联系和原因了解不足，未来的预报受到阻碍。降雨量和温度记录相对较短，质量较差。少数长期记录表明，厄尔尼诺年后，春雨较多，夏季主要降水减少，而正常/拉尼娜年，春雨变化/减少，夏季降水稳定。然而，这种关系太弱，不能进行干旱预报，而且校准时间太短。此外，春雨也会导致饥荒；其原因更为复杂，到目前为止，春雨不足的情况是不可预测的。今年夏天，出人意料的夏季过度降雨导致包括埃塞俄比亚在内的北半球热带非洲大部分地区发生洪水。在未来气候变化的气候模式情景下预测增强的季节性降水范围需要长时间、高分辨率的气候记录，以调查降雨多变性的性质、任一场降雨失败的频率以及调查气候中是否存在通过短仪器序列无法检测到的较长期周期性。一种特别有效的方法将是利用日期确定的替代材料来推导出过去气候变异性的独立测试。最近在理解钙质洞穴沉积(洞穴降水)参数的气候意义方面取得的快速进展，再加上我们在埃塞俄比亚的试点工作，表明洞穴沉积记录是解决埃塞俄比亚这一紧迫问题的最佳前景，因为到目前为止，其他潜在的替代方法未能产生高分辨率的气候重建。在这里，我们建议通过对过去一千年来生长的洞穴植被的多参数分析来获得古气候参数，如平均年降水量、季节性和年水分过剩。每个单独参数的不确定性将来自分析系列中的噪声，并通过对同一地理位置的不同样本重复分析不同的替代物来获得。因此，我们的目标是将气候系列重建为可由气候模型建模并因此用于验证的定量参数。

The Ethiopian highlands are a classic example of a rain-sensitive region where future forecasts are hampered by inadequate understanding of historical patterns, their wider associations, and causes. Rainfall and temperature records are relatively short and of poor quality. The few long records demonstrate that after El Niño years, the spring rains are heavy and the main summer rains are reduced, whereas in normal / La Nina years, spring rains are variable / reduced and the summer rains are stable. However this relationship is too weak to enable drought forecasts and the calibration time period is too short. In addition, the spring rains also fail and lead to famine; their cause is more complicated and spring rainfall failures are, to date, not predictable. This summer, unpredicted excessive summer rains caused flooding over most of northern hemisphere tropical Africa, including Ethiopia. An enhanced seasonal precipitation range is predicted under climate model scenarios of future climate change Long, high resolution climate records are required to investigate the nature of rainfall variability, the frequency of failure of either rain, as well as investigate the presence of longer term periodicity in climate that cannot be detected through short instrumental series. A particularly powerful approach will be to make use of well-dated proxy material to derive independent tests of past climate variability. Recent rapid advances in the understanding of the climatic meaning of parameters derived from calcareous speleothems (cave precipitates), coupled with our pilot work in Ethiopia, indicates that speleothem records are the best prospect for tackling this urgent problem in Ethiopia, as to date other potential proxies have failed to yield high resolution climate reconstructions. Here we propose to derive palaeoclimatic parameters such as mean annual precipitation, seasonality and annual moisture excess through the multiparameter analysis of speleothems that have grown over the last millenium. Uncertainty on each of the individual parameters will be derived from the noise in analytical series and by repeating analyses of different proxies on different samples from the same geographic location. We therefore aim to reconstruct climate series as quantitative parameters that can be modelled by, and therefore used to validate, climate models.