Carbon dioxide produced by human metabolism rose 74% between 1985 and 2015 to 2.05 billion metric tons a year, a study led by the University of Bath estimates, the university said in a release republished by ScienceDaily on Nov. 7. The study was published in The Lancet Planetary Health.
Related: COP31 Opens in Antalya With U.S. Absent and 1.5C Off Track.
What the study found
The team calculated that metabolic CO2 grew from 1.18 billion metric tons in 1985 to 2.05 billion in 2015, according to Bath. More than 60% of the increase came from the growing number of people, the university said. Changes in how much CO2 each person produces played a much smaller role.
The researchers combined thousands of measurements of CO2 output across the human lifespan with global population and body-weight data, Bath said.
Why breathing is not like burning fuel
The researchers stressed that exhaled CO2 differs from fossil fuel emissions, according to the release. Most of the carbon people breathe out comes from food, which plants recently pulled from the air. Burning coal, oil and gas releases carbon that stayed underground for millions of years, the university said.
“We’re not saying that breathing is driving climate change,” lead researcher Javier Gonzalez of Bath’s Centre for Exercise, Nutrition and Metabolism said in the release.
Why it matters
The estimate can help scientists build more complete carbon budgets, Bath said. Human metabolism can noticeably affect local carbon measurements in dense cities, according to the release. The researchers are not recommending that people change their diets or exercise to reduce it. See more in Science.
Sources
- ScienceDaily (University of Bath release): Human bodies produce 2 billion metric tons of CO2 a year just by staying alive
- The Lancet Planetary Health: Accounting for global carbon dioxide production from human metabolism between 1985 and 2015
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