Does Breathing Add To Climate Change?

Written By Teacher: Liz Ransom

As a High School Spanish teacher and student newspaper advisor, Liz has taught for over 20 years and has served as World Languages Department Chair and K-6 summer camp activities leader. She has worked in Ohio, Maine, New Jersey, Maryland, and Chile.

Curious children and teens might wonder how breathing impacts climate change after learning about concepts such as the carbon cycle, as in this K-2 science lesson Life in Soil, or about carbon emissions, such as in the lessons Renewable Energy and Engineering (grades 3-5) and Carbon Sequestration (grades 9-12). Students will be glad to know that human respiration is a  part of the “closed-loop” carbon cycle and does not contribute to climate change. The “bathtub” metaphor used in this Climate Explainer can also be found in the Inquire section of the 9-12 EnRoads Climate Change Solutions lesson.

Written By: MIT Environmental Solutions Initiative

The MIT Climate Change Engagement Program, a part of MIT Climate HQ, provides the public with nonpartisan, easy-to-understand, and scientifically-grounded information on climate change and its solutions.

We inhale oxygen; we exhale carbon dioxide (CO2). This simple story of human respiration is one many of us remember from grade school science class. And because humanity’s CO2 emissions are driving climate change, it’s natural to wonder whether all the carbon people breathe out is warming the planet, especially as the global population climbs.

As MIT professor of biology Penny Chisholm explains, though, we can breathe easy: Human respiration does not contribute to climate change.

That’s because the CO2 humans exhale is part of a closed loop. During the process of photosynthesis, plants take in CO2 from the air and soil and store the carbon in their tissues. When people eat those plants, or eat the animals that ate those plants, we ingest that carbon. And that’s the carbon in the CO2 we eventually breathe out. Once we exhale it, it returns to the atmosphere, and the cycle begins again.

“There's no net increase in CO2 in the atmosphere, because it just came from the atmosphere via plants, went into you, and went back out,” Chisholm says.