Plant gases help curb global warming, finds study

Plants respond to warming temperatures by emitting vapors that help reflect sunlight, a team of scientists have discovered.

Melanie Stetson Freeman / The Christian Science Monitor / File
An aerial view of Tongass National Forest near Ketchikan, Alaska. Tongass is the largest national forest in the United States.

It's well known that plants can help mitigate global warming, by absorbing carbon dioxide and trapping it, via photosynthesis, in things like leaves, stalks, and branches.

But it turns out that plants help cool the planet in another way, by releasing tiny particles into the atmosphere that help reflect sunlight back into space. 

Yes, it's true: Plants pass gas. A new study published in the journal Nature Geoscience found that vapors emitted by plants scatter and absorb radiation from the sun, and that they help form cloud droplets that also reflect the sun's rays. 

"Everyone knows the scent of the forest," said study co-author Ari Asmi, in a press release from the University of Helsinki. "That scent is made up of these gases."  

The scientists measured concentrations plant vapors and other aerosols at 11 different sites around the globe – seven in Europe, two in North America, and the others in Siberia and South Africa – and recorded the temperature. They found that, as temperatures increased, the plants emitted more vapors, effectively responding to the warming by increasing the cooling effect.

So does that mean we are good then? Do the global cooling emissions from plants offset the global warming emissions coming from a Chevy Camaro's tailpipe?

Not quite. The scientists found that the effect of the increased plant emissions counters only about 1 percent of global warming. “This does not save us from climate warming,” said study co-author Pauli Paasonen, in the press release. 

But the plant gasses still might cool things for you locally, especially if you live in a rural, forested area. The study found that, in places where there is little man-made soot in the air, the effect could counteract up to 30 percent of warming.

And this discovery has the potential to improve our understanding of how and why our climate is changing. Aerosols, that is, tiny solid or liquid particles that hang in the air, are one of the least understood aspects of our atmosphere.  "Understanding this mechanism could help us reduce those uncertainties and make the models better,” said Paasonen.

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