Increases in atmospheric carbon dioxide can make trees grow faster and accumulate more biomass. A study in a forest in North Carolina found that trees exposed to elevated CO2 had 21% more aboveground biomass. The way trees grow and their size relationships also changed under elevated CO2, leading to a 27% increase in biomass for the dominant tree species. This shows that understanding how trees change in response to CO2 levels is important for accurately estimating their biomass.