Arctic temperatures rise when plants stop breathing

Plants have a major influence on Arctic warming and melting sea ice, according to a new study from Pohang University of Science and Technology (POSHTECH). Arctic temperatures rise when plants shut down a process that naturally cools their surroundings.

Plants release a water vapor that lowers the land surface temperature around them during transpiration, but higher levels of atmospheric CO2 are disrupting this system.

During photosynthesis, the stomata of plant leaves open to absorb CO2 from the air, while simultaneously releasing moisture. But when CO2 levels rise, the plants can absorb enough CO2 without opening their stomata. As a result, less water vapor is released. 

The land temperature can rise rapidly with diminished transpiration. A decrease in transpiration was recently cited as one of the causes of increasingly frequent and intense heat waves in the northern hemisphere.

The widespread response of plants to higher atmospheric CO2 contributes to climate change by controlling the exchange of energy between Earth’s surface and atmosphere, which is referred to as “physiological forcing.” 

The POSHTECH study is the first to confirm the effects of physiological forcing on the Arctic climate system.

For the investigation, the research team analyzed Earth system models (ESM) simulations. The experts confirmed that an increase in CO2 causes stomatal closure in land vegetation and subsequent land warming, which ultimately accelerates Arctic warming.

The researchers estimated the extent of the Arctic warming linked to stomatal closure and found that about 10 percent of the greenhouse effect is caused by this type of physiological forcing.

“The stomatal closure effect due to the increased CO2 levels is not fully counted in the future climate projection,” said study co-author Professor Jong-Seong Kug. “This means that Arctic warming can proceed much faster than the current forecast.” 

“The increase in CO2 is accelerating global warming not only through the greenhouse effect that we all knew of, but also by changing the physiological function of plants.”

The study is published in the journal Nature Communications.

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By Chrissy Sexton, Earth.com Staff