What climate scientists learned from a N.H. forest

For a decade, scientists have been studying trees at New Hampshire’s Hubbard Brook Experimental Forest to learn more about how the forest can mitigate climate change as a “carbon sink” capturing greenhouse gas emissions.

But just letting trees do the work of sucking up carbon might not work as well as some climate models assume, they found in a new study published in Proceedings of the National Academy of Science.

While warmer temperatures in the summer can boost how much carbon trees store by 63 percent, those benefits are cut in half by warmer winters that melt the insulating winter snow, according to the study.

When the snow melts, tree roots can get damaged in freeze/thaw cycles, limiting how well the trees can absorb nutrients such as carbon.

“Temperate forests aren’t as large a climate safety net as previously expected, since half its warming-induced ability to sequester carbon unravel due to a smaller winter snowpack,” said Emerson Conrad-Rooney, the study’s lead author and a PhD student at Boston University.

Right now, forests absorb enough carbon to offset about one-fifth of the country’s annual fossil-fuel emissions, according to the study. But, the scientists warned, warmer temperatures could erase that benefit.

The study suggests that current models likely overestimate how much carbon temperate forests — those in the temperate zone between the tropical and polar regions — can store because they aren’t accounting for the negative impacts of a shrinking snowpack. The authors said an update to those models is likely due.

“Our decade-long experiment shows why Earth-system models need to incorporate how ecosystem processes respond to changes in winter climate, not just warmer summers,” said Andrew B. Reinmann, a co-author and assistant professor at City University of New York.

This story first appeared in Globe NH | Morning Report, our free newsletter focused on the news you need to know about New Hampshire, including great coverage from the Boston Globe and links to interesting articles from other places. If you’d like to receive it via e-mail Monday through Friday,you can sign up here.

Amanda Gokee can be reached at amanda.gokee@globe.com. Follow her @amanda_gokee.