Advertisement

Fact check: False claim that weight of CO2 molecule means it can't rise or cause warming

Eleanor McCrary, USA TODAY
·3 min read

The claim: CO2 is too heavy to add to greenhouse gas effect

An image attached to Jan. 12 Instagram post (direct link, archive link) shows clouds spelling out "CO2" against a blue sky.

"CO2 has a molecular weight of just over 44 while air – mainly oxygen and nitrogen – has a molecular weight of only 29," reads the post. "The specific gravity of CO2 is some 1.5 times greater than air. That would suggest that CO2 exhaust gases from vehicles or power plants do not rise into the atmosphere some 12 miles or more above Earth to form the feared greenhouse effect."

It was liked nearly 7,000 times in two weeks.

Follow us on Facebook! Like our page to get updates throughout the day on our latest debunks

Our rating: False

Gases – including CO2 – are constantly moving around and mixing in the lower levels of the atmosphere regardless of their weight, experts said. If gases were in stratified layers and CO2 sunk below oxygen, humans would not be able to breathe. Carbon dioxide is one of the main contributors to the greenhouse gas effect.

Gases are not separated by weight

It's true that carbon dioxide has a higher molecular weight than oxygen and nitrogen, said Suzanne Paulson, a professor of atmospheric and oceanic science at the University of California in Los Angeles.

However, it still rises into the atmosphere.

The homosphere, which extends about 60 miles from the ground, is an area where gases are mixed and do not separate by their mass, Paulson said. This is partly caused by wind and other turbulent air motions, according to a 1999 article in the journal International Geophysics.

Even without winds, the gases would still mix, Paulson said. It is their nature to move around constantly "like little billiard balls."

Fact check: No, a volcano in Greece did not produce more CO2 than all humans combined

If this mixing did not occur, gases would be in stratified layers – and humans would not be able to survive.

Paulson, along with some of her students, calculated that if CO2 did not rise into the atmosphere, the Earth would be covered in an 11-foot-thick layer of carbon dioxide.

"CO2 at moderate concentrations makes you sleepy, but if it were pure CO2 – or even majority CO2 – we would have all been asphyxiated due to lack of oxygen," said Paulson, who is also director of UCLA's Center for Clean Air.

Instead, carbon dioxide intermingles with other molecules. It also absorbs infrared radiation and re-radiates it back to Earth, causing a warming effect, said Dennis Baldocchi, a biometeorology professor at the University of California in Berkeley.

That's why carbon dioxide is one of the main contributors to the greenhouse gas effect and global warming.

USA TODAY has debunked an array of CO2-related misinformation, including claims that one eruption of Mt. Etna in Italy released 10,000 times more CO2 than humans ever have and that CO2 is not a problem because it is involved in photosynthesis.

USA TODAY reached out to the social media user who shared the post for comment.

Our fact-check sources:

Thank you for supporting our journalism. You can subscribe to our print edition, ad-free app or electronic newspaper replica here.

Our fact-check work is supported in part by a grant from Facebook.

This article originally appeared on USA TODAY: Fact check: CO2 rises and spurs warming, despite molecule's weight