Collaborative Research: Multicentury Drought Reconstructions from Guatemala and the Context for Past and Future Hydroclimatic Change

虽然人为气候变化的特征与观察到的和持续的气温上升有关，但伴随而来的降水变化以及干旱的频率和持续时间将对人类人口产生最直接和最直接的后果。区域水文气候的变化将加剧人口增长、污染、基础设施衰落和资源冲突对可持续水资源供应的威胁。政府间气候变化专门委员会(IPCC)最新气候模型的一个强有力的预测是，在未来温室气体增加的情况下，危地马拉和中美洲大部分地区的降雨率在夏季和冬季都将下降。缓解水资源供应变化的后果的关键是对降水变化的潜在范围以及将这一知识纳入水规划和自然资源政策的长期观点。然而，在危地马拉和整个中美洲热带地区，干旱的长期工具记录很少。对于高海拔地区尤其如此，这些地区很可能表现出全球气候变化最早和更严重的局部后果。在缺乏长期仪器记录的情况下，研究气候变化和变化的原因和后果的科学家依赖于可用于重建过去海洋-大气条件的替代记录。树木年轮年表构成了可用的高分辨率陆地代理记录的大部分。然而，它们几乎完全没有出现在墨西哥南部的热带美洲。该地区缺乏对干旱的高分辨率、长期视角，也限制了验证气候模型预测的机会。因此，为了了解当地对大范围强迫的反应，检测和确定与人为气候变化有关的长期趋势，以及验证用作预测未来变化的主要预测工具的气候模型的保真度，开发该地区每年可分辨的长期气候记录是必要的。研究人员将把树状气候学的地理前沿扩展到危地马拉的山区，确定对降水敏感的物种和地点，并对过去几个世纪的干旱变异性进行估计。在这项研究中，他们将调查和利用高海拔热带针叶树种的组合。将对所有候选分类群进行仔细和系统的研究，以确定年度年轮形成和年表发展。一旦测年和年表编制完成并得到核实，将把树木年轮时间序列与现有的当地和网格气象数据进行比较，以发现生理上合理的气候/生长关系。将开发模型，根据绝对日期的年轮宽度序列估计过去的气候异常。对过去降水和干旱的重建将与独立开发的气候场以及对过去强迫的估计进行客观比较。干旱重建还将被用来解释气候在过去几百年的重要历史事件中可能发挥的作用。这项研究将提供干旱变异性的长期背景，这对于努力减轻气候变化对脆弱人口的影响至关重要。拟议的研究纳入了各区域玛雅社区的积极宣传和参与性教育。

While the signature of anthropogenic climatic change is associated with observed and ongoing increases in temperature, it is concomitant changes in precipitation and the frequency and duration of drought that will have the most direct and immediate consequences for human populations. Changes in regional hydroclimate will exacerbate threats to sustainable water supplies from growing populations, pollution, declining infrastructure, and resource conflicts. One robust prediction of the most recent Intergovernmental Panel on Climate Change (IPCC) climate model ensemble is that precipitation rates will decrease over Guatemala and most parts of Central America in both the summer and winter under future increased greenhouse gas scenarios. Critical to mitigating the consequences of changes in water availability is a long-term perspective on the potential range of variability in precipitation and the integration of this knowledge within water planning and natural resources policy. However, long-term instrumental records of drought are sparse in Guatemala and throughout the Central American tropics. This is particularly true for high elevation regions, which are likely to demonstrate the earliest and more severe local consequences of global climate change. In the absence of long instrumental records, scientists investigating the causes and consequences of climate variability and change depend on proxy records that can be used to reconstruct past ocean-atmosphere conditions. Tree-ring chronologies form the bulk of the available, high-resolution terrestrial proxy records. However, they are almost entirely absent from the tropical Americas south of Mexico. The lack of a high resolution, long-term perspective on drought from this region also limits opportunities to validate climate model predictions. The development of long, annually resolved records of climate from this region is therefore necessary for understanding the local response to broad-scale forcing, detecting and attributing long-term trends related to anthropogenic climate change, and verifying the fidelity of the climate models used as the primary forecasting tool for predicting future change.The investigators will expand the geographic frontier of dendroclimatology into the mountains of Guatemala, identifying species and sites which show sensitivity to precipitation, and developing estimates of drought variability over the last several centuries. They will investigate and utilize a combination of high elevation tropical conifer species in this study. All candidate taxa will be carefully and systematically examined to establish annual ring formation and chronology development. Once dating and chronology development has been completed and verified, the tree-ring time series will be compared against the available local and gridded meteorological data in order to detect physiologically reasonable climate/growth relationships. Models will be developed to estimate past climate anomalies from the absolutely dated ring width series. Reconstructions of past precipitation and drought will be objectively compared against independently developed climate fields as well as estimates of past forcing. The drought reconstructions will also be used to interpret the possible role of climate in important historical events of the last several hundred years. This research will provide a long-term context for drought variability that is critical for efforts to mitigate the consequences for vulnerable human populations from climatic change. Active outreach and participatory education in Maya communities in the regions are integrated in the proposed research.