Dendrochronology is the science of using exactly dated wood from old growth trees to infer or reconstruct information about the Earth’s environmental system. The science of dendrochronology involves studying variations in the radial growth among individual trees forming a given forest stand and uses the practice of cross dating to precisely date the collected wood samples to an exact calendar year. After processing, the resulting annual tree-ring records are used to reconstruct the spatial and temporal patterns of processes related to climate and the natural environment, as well as related societal impacts.

There are multiple sub-disciplines of dendrochronology, such as dendroclimatology, dendroarchaeology, dendroecology, dendrogeomorphology, dendroglaciology or dendrohydrology among others. The specific projects within PIRE-CREATE are associated with dendroecology and dendroclimatology.

Problems that can be addressed using dendroecological techniques include studies of widespread outbreaks of herbivorous insects in forests, tree decline and forest dieback, or distinct tree behavior driven by the rising concentration of atmospheric CO2 and other gases. Within the PIRE-CREATE context, we are working to find tropical tree species sensitive to climate variations to fill an important gap in knowledge of the tropical regions of South America, which lack tree-ring data in comparison with temperate regions of the Americas. For example, recently Laia Andreu-Hayles, a PIRE-CREATE scientist, and collaborators have confirmed annual periodicity using radiocarbon analyses for a Brazilian Cedrela odorata tree-ring chronology found in Ecuador.

By using tree-ring records, we can quantitatively infer temperature and precipitation values from past centuries with annual and even seasonal resolution with the only limitation being the age of the trees. Dendroclimatic reconstructions are based on the principle that the radial growth of trees is limited by the environmental conditions of their surroundings. The relevance and significance of dendroclimatological studies lies in its ability to develop long climate reconstructions beyond the relatively short instrumental record, facilitating a much more comprehensive view of the climate system.

Several reconstructions have contributed to understanding past climate variability and trends, especially during the last millennium (see Esper et al., 2016 for a review), highlighting the unprecedented recent warming of the second part of the 20th century and the 21st century. Some results also show that modern hydroclimatic variations may have at times been exceeded in magnitude and duration. However, a recent study led by Park Williams, a PIRE-CREATE scientist,  is already linking anthropogenic warming to an emerging North American megadrought.

As part of the PIRE CREATE Project, scientists use insights gained from dendroclimatology to explore many aspects of climate change. Across the Americas, scientists use information from trees to study changes in megadroughts and look for continental-scale influences of ocean surface temperature changes. In Argentina and Peru, scientists use trees in the Andes to study changes in atmospheric general circulation such as the expansion of the Hadley cells. In Peru, Bolivia, and Brazil, trees are being used to study changes in South American Monsoon variability. In Brazil, urban climate is studied by examining metal traces found in tree wood.

PIRE CREATE project in the news:

Several reconstructions have contributed to understanding past climate variability and trends, especially during the last millennium, highlighting the unprecedented warming during the second part of the 20th century and in the 21st century. Some results also show that modern hydroclimatic variations may have at times been exceeded in magnitude and duration. However, a recent study led by Park Williams, a PIRE-CREATE scientist,  is already linking anthropogenic warming to an emerging North American megadrought (Williams et al. 2020 Science).

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FULL MOVIE: CHASING TRACES FROM THE PAST:

In this documentary movie , Ernesto Tejedor, researcher from the PIRE CREATE Project and researchers from the University of Zaragoza will make a journey through isolated lakes, ancient forests, remote glaciers, deep caves and rare historical manuscripts, chasing those evidences that allow us to infer past climate conditions beyond the instrumental period. Besides, some of the most important scientists in their fields, will accompany us in this adventure to discover the climate secrets stored in those evidences. Understanding the climate of the past will help contextualizing the current warming and that would mean better adaptation in the future.