On the outside, its rust-red bark had peeled. Its sweet, distinct cedar smell had disappeared.

But at its core, it’s still as hard as a tabletop – and may just contain a way of slowing down rapidly rising temperatures.

A 3,775-year-old log unintentionally discovered under a farm in Canada may point to a deceptively simple method of locking climate-warming carbon out of the atmosphere for thousands of years, according to a study published Thursday.

“This accidental discovery really gave a critical data point,” said Ning Zeng, a University of Maryland climate scientist whose team unearthed the ancient chunk of wood.

“It’s a single data point,” he added, but it “provides the data point we need to really say under what conditions we can preserve wood for a thousand years or longer.”

Figuring out ways of sequestering carbon may be crucial to meeting the world’s goal of halting warming beyond 2 degrees Celsius above preindustrial levels, which scientists agree is necessary for forestalling the most disastrous consequences of climate change.

Doing something as simple as burying wood underground in the right spot, these researchers say, may be a cheap and scalable way of doing just that.

Forests are Earth’s lungs, sucking up six times more carbon dioxide (CO2) than the amount people pump into the atmosphere every year by burning coal and other fossil fuels.

But much of that carbon quickly makes its way back into the air once insects, fungi and bacteria chew through leafs and other plant material. Even wood, the hardiest part of a tree, will succumb within a few decades to these decomposers.

What if that decay could be delayed? Under the right conditions, tons of wood could be buried underground in wood vaults, locking in a portion of human-generated CO2 for potentially thousands of years. While other carbon-capture technologies rely on expensive and energy-intensive machines to extract CO2, the tools for putting wood underground are simple: a tractor and a backhoe.

Finding the right conditions to impede decomposition over millennia is the tough part. To test the idea, Zeng worked with colleagues in Quebec to entomb wood under clay soil on a crop field about 30 miles east of Montreal.

“We were trying to do a small pilot project at first,” said Ghislain Poisson, an agronomist with Quebec’s agricultural ministry who worked with Zeng. “At the time, I was already thinking that it was a good place to do this.”

But when the scientists went digging in 2013, they uncovered something unexpected: A piece of wood already buried about 6½ feet underground. The craggy, waterlogged piece of eastern red cedar appeared remarkably well preserved.

“I remember standing there looking at other people, thinking, ‘Do we really need to continue this experiment?’” Zeng recalled. “Because here’s the evidence.”

“I actually got a little otherworldly feeling,” he added. “We immediately understood this was a very old piece.”

Radiocarbon dating revealed the log to be 3,775 years old, give or take a few decades. Comparing the old chunk of wood to a freshly cut piece of cedar showed the ancient log lost less than 5 percent of its carbon over the millennia.

The log was surrounded by stagnant, oxygen-deprived groundwater and covered by an impermeable layer of clay, preventing fungi and insects from consuming the wood. Lignin, a tough material that gives trees their strength, protected the wood’s carbohydrates from subterranean bacteria. The team wrote up their results in a paper in the journal Science.

“This is a very interesting paper with practical applications for fighting climate change,” said Daniel L. Sanchez, an assistant professor at the University of California at Berkeley who was not involved in the study. “Scientists and entrepreneurs have long contemplated burying wood as a climate solution.”

The next step is to find prehistoric logs in other locations, to see how well other types of soil preserve wood. And Zeng and his colleague did continue with their experiment vaulting their own wood underground. For now, Zeng brought a slice of the ancient log unearthed in Quebec to show off at Climate Week in New York.

The researchers estimate buried wood can sequester up 10 billion tons of CO2 per year, which is more than a quarter of annual global emissions from energy, according to the International Energy Agency.

One of the biggest challenges isn’t so much the supply of wood but rather the cost of transporting it to the right spots, Poisson said. “There’s probably a lot of unmerchantable wood right now that doesn’t have any market or doesn’t have any purpose.”

There’s an irony to the idea of entombing wood to stall climate change, Zeng points out. Coal, one of the main fossil fuels responsible for rising temperatures, is formed when vegetation is buried underground for millions of years. Ever since the Industrial Revolution, of course, people have mined and burned coal for energy.

In a sense, a wood vault simply reverses that process.