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

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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.