Witness trees are rewriting America’s climate timeline

witness trees – From cores pencil-thin to centuries-old, tree rings are extending U.S. climate records—capturing droughts, volcanic cooling, El Niño-linked patterns, and hurricane scars long before satellites. Researchers say the longer the record, the sharper the forecast be

By the time the 2026 hurricane season is in full motion and a strong El Niño looms over global weather patterns, scientists are still turning to one of the oldest data sources on Earth: living trees.

In forests across Alaska, Arizona and far beyond, researchers keep pulling narrow, pencil-diameter cores from ancient trunks. In the rings they uncover. they say they can read centuries of storms and dry spells—floods. droughts. and hurricane landfalls—sometimes extending what modern satellites can show by hundreds of years.

For tree scientists, it’s not abstract science. The rings carry the memory of damage and recovery: reduced growth, blocked sunlight, regional cooling, and the trauma left behind when extreme weather breaks, strips, and stunts a tree’s life.

Nicole Davi. a tree scientist at William Paterson University and an adjunct scientist in the Tree-Ring Laboratory at the Lamont-Doherty Earth Observatory. said the evidence stored in tree rings can be “thrilling.” During the U.S. celebration of its 250th anniversary. she marveled at still-living trees that were already growing in 1776—living witnesses to the weather history that helped shape the country.

People call some of these trees “witness trees,” Davi said. “They were there, right?”

The method is precise, and the scale is massive. Researchers compare the width, density and spacing of tree rings across regions. Under a microscope. Davi said. a core slice from trees sensitive to temperature change can illustrate historic volcanic eruptions. with patterns showing reduced growth tied to blocked sunlight and regional cooling. She described seeing volcanic impacts in places spanning “Mongolia to Canada to Alaska.”.

Valerie Trouet. a professor in the Laboratory of Tree-Ring Research at the University of Arizona. called finding the right trees one of the best parts of the job. “You arrive and you see these ancient old trees, in a beautiful landscape,” she said. “You’re among these organisms that have been there for centuries, literally many generations before you’ve been there.”.

Her work often begins with travel into remote. high-mountain forests. where searching for the oldest trees can turn into an expedition. Trouet said that when she finally sees the rings, “it’s so exciting.” She also pointed to how regions matter. When researchers target drought. for example. they look for tree rings in areas that are drier. where growth is dominated by moisture.

In Tucson, Trouet said trees grow more in wet years. In dry years, they don’t have enough water to create new wood, leaving behind rings that are “really narrow.”

That same need for careful selection shapes what scientists can learn about climate events with repeating cycles. Collecting tree ring data to study events like El Niño helps fill in the history that existed before satellites were available, Trouet said.

But she also warned how limited direct observation can be. With 50 to 60 years of data and a cycle that spans six or seven years, she said researchers are left with fewer than ten El Niños to study. “That’s not a lot, especially for statistical analysis.”

Expanding the record means widening the geographic net. Trouet said comparing cores from other regions where climate and rainfall patterns are strongly affected by El Niño can improve the analysis of how often events occur and how they interact with other forces.

Hurricane memory can also be read in the wood. Tree ring samples taken in areas previously hit by hurricanes can reveal not only impacts from long-ago storms but also how more recent storms have affected trees. Trouet said. For example. she said tree rings have shown how Hurricane Harvey’s intense flooding in Texas affected tree growth and how rain storms are intensifying.

Studies have shown that tree growth slowed in the year after a hurricane, she said. When trees remain standing, they can lose leaves and big limbs, and that trauma shows up in their rings.

Davi described finding evidence of hurricanes in “gorgeous” old, “stunted and gnarly” trees in coastal New York and New Jersey. She connected reliability to duration: “The really big (hurricanes) don’t happen that often,” she said. “The longer record you have, the more reliable idea you have of how often these hurricanes happen.”.

Researchers do not read tree rings in isolation. They cross-reference tree information to understand how wildfires strike the Pacific Northwest during El Niño years and the Southwest during La Niña years. The rings also help study how expansive or prevalent wildfires were in the past.

Taken together. the work ties the same physical markers—ring width. density. spacing—to very different extremes: drought and volcanic cooling. storm surges and hurricane landfalls. wildfire patterns linked to El Niño and La Niña years. The common thread is time. The rings offer a record that stretches well beyond the era when instruments and satellites could watch every shift in the sky.

What fascinates Davi is not only that trees are storing stories, but what those stories can reveal about resilience to traumatic weather events. “But she adds it’s ‘super exciting scientifically’ to look forward to what more trees could tell us about events that shape our histories.”

In a world heading into a potentially disruptive hurricane season while El Niño conditions build, researchers say the most important field tool isn’t a new device—it’s the patient, still-living record already embedded in wood that has survived.

tree rings witness trees El Niño hurricanes Hurricane Harvey drought volcanic eruptions wildfire climate records University of Arizona Lamont-Doherty Earth Observatory William Paterson University