After controlling for other variables, scientists concluded that the change resulted largely from the increase in carbon dioxide, a major factor in climate change.

Image Forests along the Eastern Seaboard are responding to increasing carbon dioxide levels. Credit... Ethan Gilsdorf for The New York Times

Trees are now known to play a vital role in countering global warming because they absorb and store carbon dioxide, the leading heat-trapping gas.

Geoffrey G. Parker, a co-author of the paper and an ecologist with the Smithsonian Environmental Research Center in Edgewater, Md., said his research indicated that the local forests were adapting to the rise in carbon dioxide by absorbing more.

“My guess is that they are already sopping up some of the extra carbon,” he said.

But Dr. Parker said it was unclear whether the trend could be sustained. “We don’t think this can persist for too long because other limiting factors will come into play, like water availability and soil nutrients,” he said.

Since 1987, Dr. Parker has been studying 55 stands of trees along the bay’s western edge. Recent censuses have shown that compared with the earlier years, the trees are packing on weight at an additional two tons per acre annually. The scientists track the speed of growth through tree diameter.