FACT BRIEF

Are carbon dioxide emissions from human activities enough to affect the climate?

Thursday, July 8, 2021

By John Cook

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YES

The carbon cycle naturally moves a large amount of carbon dioxide through the climate system. For example, in spring, vegetation increases, absorbing CO2. In the winter, vegetation dies, emitting CO2. Natural CO2 emissions roughly balance natural CO2 absorptions.

The misconception that CO2 from human activities cannot influence the climate because it is too small compared to natural CO2 emissions fails to recognize that introducing even a modest new source of CO2 throws off Earth’s carbon balance. The land and oceans have not adequately absorbed the CO2 humans have released since the Industrial Revolution, causing atmospheric CO2 to spike.

For 800,000 years, atmospheric CO2 remained roughly in balance, moving slowly between 170 and 300 parts per million. Due to activities such as burning fossil fuels, deforestation, and land-use changes, atmospheric CO2 reached 416 parts per million in February 2021 — a nearly 50% increase from preindustrial times.

See a full discussion of this at Skeptical Science

This fact brief is responsive to conversations such as this one.

Sources

NASA Earth Observatory: The carbon cycle

NASA Vital Signs: Carbon dioxide measurements

Reuters CO2 levels to breach 50% rise from pre-industrial era in 2021 - Met Office

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Skeptical Science

Skeptical Science is a non-profit science education organization. Our goal is to remove a roadblock to climate action by building public resilience against climate misinformation. We achieve this by publishing debunking of climate myths as well as providing resources for educators, communicators, scientists, and the general public. Skeptical Science was founded and is led by John Cook, a Senior Research Fellow with the Melbourne Centre for Behaviour Change at the University of Melbourne.

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