The revolt of the plants: The Arctic melts when plants stop breathing

The joint research team led by Professor Jong-Seong Kug and doctoral candidate So Won Park of POSTECH's Division of Environmental Science and Engineering, and Researcher Jin-Soo Kim of the University of Zurich has confirmed that the increase in atmospheric CO₂ concentration closes the pores (stomata) of plants in high-latitude areas and reduces their transpiration, which ultimately accelerates Arctic warming. The findings, which were studied through the Earth system models (ESM) simulations, were recently published in Nature Communications, an authoritative journal in science.

Plants take in CO₂ and emit oxygen through photosynthesis. During this process, the stomata of leaves open to absorb CO₂ in the air and release moisture at the same time.

However, when the CO₂ concentration rises, plants can absorb enough CO₂ without opening their stomata widely. If the stomata open narrowly, the amount of water vapor released also decreases. When this transpiration of plants declines, the land temperature rapidly rises under greenhouse warming. Recently, such a decrease in transpiration has been cited as one of the reasons for the surge in heat waves in the northern hemisphere.

This response from the vegetation leads to the global climate change by controlling the exchange of energy between the surface and atmosphere, referred to as 'physiological forcing.' But so far, no study has confirmed the effects of physiological forcing on the Arctic climate system.

The joint research team analyzed the EMS simulation and confirmed that the increase in CO₂ leads to stomatal closure in land vegetation causing land warming, which in turn remotely speeds up Artic warming through an atmospheric circulation and positive feedback in Earth systems process.

In addition, a quantitative estimate of the stomatal closure's effect on Arctic warming due to increased CO₂ showed that about 10% of the greenhouse effect is caused by this physiological forcing.

Professor Jong-Seong Kug, who has studied Arctic warming in a variety of perspectives, commented, "The stomatal closure effect due to the increased CO₂ levels is not fully counted in the future climate projection." He pointed out, "This means that Arctic warming can proceed much faster than current forecast." He also warned that "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."

This research was financially supported by the climate feedback research in the land-ocean biogeochemistry division of the National Research Foundation of Korea.