Intensively managed grazing is often touted as a nature-based climate solution that can increase the amount of carbon a pasture removes from the atmosphere, reducing atmospheric carbon dioxide. We tested this assertion at an intensively grazed pasture in Maine by quantifying the amount of carbon taken up and released by the pasture over two years. We found that, contrary to expectations, the pasture was carbon neutral or actually a source of carbon to the atmosphere. Further analysis revealed that the ability of the cool season grasses that dominate the pasture to remove carbon from the atmosphere via photosynthesis was limited by hotter and drier weather during the summer. Our results call into question the use of intensive grazing as a nature-based solution in pastures dominated by cool season grasses in the northeastern U.S.