What was done
The authors "synthesized field measurements, satellite image analyses, and empirical models to evaluate forest and carbon cycle impacts for historical tropical cyclones from 1851 to 2000 over the continental U.S."

What was learned
Zeng et al. report "there were more forest impacts and greater biomass loss between 1851 and 1900 than during the 20th century." On average, for example, they found that "147 million trees were affected each year between 1851 and 1900," which led to "a 79-Tg annual biomass loss." Average annual forest impact and biomass loss between 1900 and 2000, on the other hand, "were 72 million trees and 39 Tg, which were only half of the impacts before 1900," which results they say are in "accordance with historical records showing that Atlantic tropical cyclones were more active during the period from 1870 to 1900." In addition, they note that the amount of carbon released from the downed and damaged trees "reached a maximum value in 1896, after which it continuously decreased until 1978," whereupon it leveled off for the remaining two decades of the 20th century.

What it means
Contrary to climate-alarmist claims that storms such as tropical cyclones and hurricanes become stronger and occur more frequently in response to global warming, thereby also creating more damage and destruction, the six U.S. scientists found that just the opposite has occurred over the course of the Industrial Revolution in the United States with respect to a major component of the natural environment (i.e., trees), as opposed to the "built" environment of American society.