University of Bath: human metabolism produced 2.05 billion tonnes of CO₂ in 2015, up 74% since 1985
A modelling study estimates that CO₂ produced as human bodies turn food into energy reached 2.05 billion tonnes a year, which refines global carbon accounting.
A study led by the University of Bath has estimated that the carbon dioxide produced by humans as their bodies turn food into energy rose by 74% between 1985 and 2015, reaching 2.05 billion tonnes a year, according to eurekalert.org eurekalert.org
eurekalert.orgeurekalert.orgOpen source ↗. The paper was published in The Lancet Planetary Health and led by Professor Javier Gonzalez of the university's Centre for Exercise, Nutrition and Metabolism. The global amount grew from 1.18 billion tonnes in 1985 to 2.05 billion tonnes in 2015.
Data and result
The researchers used thousands of real-world measurements of people from infancy to old age, showing how much CO₂ their bodies produced during everyday life. They combined these with global population and body-weight data. The work is a modelling study, and the authors acted on behalf of the IAEA Doubly Labelled Water Database Consortium writing group.
Population growth accounted for more than 60% of the increase. According to the authors, the main reason for the rise was the growing number of people, not a major increase in the amount produced by each person.
The authors come from the University of Bath, Manchester Metropolitan University, Liverpool John Moores University, Auckland University of Technology, the University of Castilla-La Mancha and the Chulabhorn Royal Academy eurekalert.org
eurekalert.orgeurekalert.orgOpen source ↗.
Carbon accounting
The CO₂ people breathe out is not the same as emissions from burning fossil fuels. The carbon we exhale comes from the food we eat and is largely carbon that plants have recently taken from the atmosphere. Fossil fuels, by contrast, release carbon that has been stored underground for millions of years.
Gonzalez said that until now there was no good estimate of how much human CO₂ production adds up to worldwide. The authors say the figure gives scientists one more piece for working out where carbon comes from and where it goes. Human metabolism is a sizeable part of that movement, particularly in heavily populated towns and cities.
The researchers stress that breathing is not driving climate change. The findings concern carbon accounting and do not suggest that people should exercise less or change what they eat eurekalert.org
eurekalert.orgeurekalert.orgOpen source ↗. According to Gonzalez, a clearer picture of human CO₂ production can help improve the accuracy of predictions for carbon reduction programmes.
