PAlaeo-Constraints on Monsoon Evolution and Dynamics

季风系统影响着世界一半以上地区的供水和生计。观测时间太短，无法估计与未来有关的多年时间尺度上的季风变化，也无法确定这一时间尺度上变化的原因。未来季风行为预测的可信度受到模拟降雨量变化的大范围传播的限制。过去的气候为克服这些问题提供了机会。这个项目将使用过去6000年来珊瑚、软体动物、洞穴和树木年轮气候变化的年度分辨古环境记录，以及全球气候模型模拟和对印度、非洲、东亚和南美季风的高分辨率模拟，以更好地了解季风动态和年际至数十年的变化。我们将使用前工业时代(公元850-1850)之前的千年作为参考气候，并将其与中全新世(MH，6000年前)的模拟和6000年前至约850年的瞬变模拟进行比较。我们将使用环境模拟来模拟观测数据，对季风变化的哪些方面由目前的模式充分反映，提供定量和全面的评估。通过将过去气候模型和未来预测联系起来，我们将评估这些预测的可信度和在十年时间尺度上发生极端事件的可能性。该项目围绕四个主题安排：(1)外部强迫和温带气候对热带辐合和热带水文循环的影响；(2)IM变率的特征，以确定外部强迫或平均气候变化对随机成分的调制程度；(3)当地(植被、沙尘)和远程因素对印度、非洲和南美洲季风持续时间、强度和模式的影响；(4)可用于评估未来季风演变可靠性的古制约因素的确定。

Monsoon systems influence the water supply and livelihoods of over half of the world. Observations are too short to provide estimates of monsoon variability on the multi-year timescale relevant to the future or to identify the causes of change on this timescale. The credibility of future projections of monsoon behavior is limited by the large spread in the simulated magnitude of precipitation changes. Past climates provide an opportunity to overcome these problems. This project will use annually-resolved palaeoenvironmental records of climate variability over the past 6000 years from corals, molluscs, speleothems and tree rings, together with global climate-model simulations and high-resolution simulations of the Indian, African, East Asia and South American monsoons, to provide a better understanding of monsoon dynamics and interannual to multidecadal variability (IM). We will use the millennium before the pre-industrial era (850-1850 CE) as the reference climate and compare this with simulations of the mid- Holocene (MH, 6000 years ago) and transient simulations from 6000 year ago to ca 850 CE. We will provide a quantitative and comprehensive assessment of what aspects of monsoon variability are adequately represented by current models, using environmental modelling to simulate the observations. By linking modelling of past climates and future projections, we will assess the credibility of these projections and the likelihood of extreme events at decadal time scales. The project is organized around four themes: (1) the impact of external forcing and extratropical climates on intertropical convergence and the hydrological cycle in the tropics; (2) characterization of IM variability to determine the extent to which the stochastic component is modulated by external forcing or changes in mean climate; (3) the influence of local (vegetation, dust) and remote factors on the duration, intensity and pattern of the Indian, African and South American monsoons; and (4) the identification of palaeo-constraints that can be used to assess the reliability of future monsoon evolution.