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测到的和持续的气温上升有关，但随之而来的降水量变化以及干旱的频率和持续时间将对人类产生最直接和最直接的影响。区域水文气候的变化将加剧人口增长、污染、基础设施下降和资源冲突对可持续供水的威胁。政府间气候变化专门委员会（气专委）气候模式集合的最新一个强有力的预测是，在未来温室气体增加的情景下，危地马拉和中美洲大部分地区的夏季和冬季降水率将下降。对减轻水供应变化的后果至关重要的是，对降水量变化的潜在范围有一个长期的看法，并将这一知识纳入水规划和自然资源政策。然而，在危地马拉和整个中美洲热带地区，干旱的长期仪器记录很少。高海拔地区尤其如此，这些地区可能最早出现全球气候变化的严重后果。在缺乏长期仪器记录的情况下，科学家们要调查气候变异和变化的原因和后果，就必须依靠代用记录来重建过去的海洋-大气状况。树轮年表构成了现有的高分辨率陆地代用记录的主体。然而，它们几乎完全不存在于墨西哥以南的热带美洲。缺乏对该地区干旱的高分辨率、长期视角也限制了验证气候模型预测的机会。因此，从该地区发展长期的、每年分辨的气候记录对于理解当地对大尺度强迫的反应、检测和归因于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是必要的。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化作出估计。他们将在这项研究中调查和利用高海拔热带针叶树种的组合。所有候选分类群将仔细和系统地检查，以建立年轮形成和年表发展。一旦测年和年代学的发展已经完成和验证，树木年轮时间序列将与现有的当地和网格气象数据进行比较，以检测生理上合理的气候/生长关系。将建立模型，从绝对定年的年轮宽度系列估计过去的气候异常。过去降水和干旱的重建将与独立开发的气候场以及过去强迫的估计进行客观的比较。干旱重建也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。这项研究将为干旱变异性提供一个长期背景，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地区玛雅社区的积极外联和参与性教育。

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.