The Historical Insights of Tree Rings

The Importance of Tree Rings in Weather and Climate Records

Tree cores extracted from some of the oldest trees on Earth are extending the historical record of past weather conditions. As the 2026 hurricane season unfolds with a robust El Niño potentially altering weather patterns globally, trees worldwide continue to document these changes. Scientists specializing in dendrochronology find the information stored in tree rings about climatic and weather events to be quite revealing. Besides revealing a tree’s age, these rings provide data on the storms, droughts, and wildfires it has endured over time. In regions like Alaska and Arizona, as well as forests globally, scientists are compiling an extensive dataset that records historical natural disasters and offers insights into future occurrences.

Thin tree cores, comparable in diameter to a pencil, are taken from ancient trees. These samples have pushed the boundaries of weather event documentation back several centuries beyond what current satellite imagery can achieve. Attributes like width, density, and spacing in the cross sections of tree rings offer evidence of floods, droughts, and hurricanes.

Witness Trees and Their Stories

Nicole Davi, a tree scientist, reflects on trees still living that have been around since 1776. Known as “witness trees,” these trees provide valuable insights into historical events because they were present to record them. Davi, a professor at William Paterson University and adjunct scientist at the Lamont-Doherty Earth Observatory, appreciates the narratives these trees offer.

Discovering the appropriate trees involves ventures into nature, one of Valerie Trouet’s favored aspects of her work. Exploring remote mountain areas and encountering ancient trees in scenic landscapes fills Trouet with awe. Associated with the Laboratory of Tree-Ring Research at the University of Arizona, Trouet captures the excitement of observing tree rings. Her adventure involves traversing forests and mountains to locate trees that hold vast historical data.

Regional Focus for Climate Research

Researchers target trees in specific areas based on the study questions they pursue. For example, research on drought necessitates examination of tree rings in arid regions where growth is heavily moisture-dependent. Trouet exemplifies the U.S. Southwest’s drought conditions. In Tucson, trees exhibit significant growth during wet years, whereas in dry periods, they lack sufficient moisture to form new wood, resulting in narrow rings.

Davi explains how microscopic examination of core slices from temperature-sensitive trees can illustrate historical volcanic eruptions. Patterns of reduced growth due to blocked sunlight and cooling effects can be observed. She mentions impressive volcanic impacts traced from Mongolia to Canada and Alaska.

Slow-growing trees in boreal forests are of particular interest for climate trend researchers. These trees offer crucial insights into long-term climate changes.

Extending Tree Ring Data

Compiling tree ring data is essential for understanding events like El Niño, especially before the era of satellites. Trouet highlights the need for a longer dataset to enhance statistical analysis of El Niño’s frequency and interactions with other events.

For areas previously affected by hurricanes, tree rings can demonstrate the impact of past and recent storms. Trouet notes tree rings have revealed how Hurricane Harvey’s flooding significantly influenced tree growth and intensified rain storms.

Research indicates that tree growth diminishes in the year following a hurricane. Trees that survive show trauma in their rings after losing leaves and substantial limbs.

Davi discovered historical hurricane evidence in old, stunted trees on the coasts of New York and New Jersey. She stresses the importance of an extended record for understanding hurricane frequency.

Scientists cross-reference tree ring data to assess wildfire prevalence in the Pacific Northwest during El Niño years and the Southwest during La Niña years. These rings assist in examining the extent of past wildfires.

Davi remarks on the resilience trees exhibit in recording traumatic weather histories, finding it scientifically fascinating to anticipate future revelations from trees regarding historically impactful events.

About the Author

Dinah Voyles Pulver, a national correspondent for USA TODAY, addresses climate change, weather, environment, and related news. Reach her at [email protected] or find her on Bluesky and X as @dinahvp or Signal as dinahvp.77.