A new analysis finds that the global human population collectively produces more than two billion metric tons of carbon dioxide each year simply by converting food into energy, a figure that has risen 74 percent over the past three decades. Researchers attribute the increase largely to population growth rather than any change in individual metabolic output. The estimate draws on data modeling the basal metabolic rates of billions of people, offering an unusually direct measure of humanity's biological footprint.
Scientists caution that this respiratory CO2 differs fundamentally from fossil fuel emissions. The carbon humans exhale was recently absorbed by plants through photosynthesis, making it part of the natural carbon cycle rather than a net addition to the atmosphere. Even so, researchers argue that quantifying human respiration more accurately could sharpen climate models, particularly in densely populated regions where biological emissions may influence local atmospheric readings. The findings, published in a peer-reviewed journal, underscore the distinction between carbon that circulates through ecosystems and carbon unlocked from underground reserves, a difference the authors say is often blurred in public discussion of emissions accounting.
Independent reporting synthesized from primary wires and global correspondents.