New measurements of the atmospheric gases wafting above a forest call into question basic estimates of how much carbon the Earth’s oceans and land masses absorb.

Researchers examine plant growth to estimate the amount of carbon dioxide plants take up during photosynthesis and the amount of oxygen they release during respiration. This information is incorporated into computer models that simulate carbon flow around the planet.

To improve estimates of the gases that vegetation inhales and exhales, Mark Battle at Bowdoin College in Brunswick, Maine, and his colleagues analysed 6 years of data on the amount of O 2 and CO 2 about 5 metres above the treetops in a New England forest.