The new study, published in Nature Geoscience, identified a negative feedback loop in which higher temperatures lead to an increase in concentrations of natural aerosols that have a cooling effect on the atmosphere.
“Plants, by reacting to changes in temperature, also moderate these changes,” IIASA and University of Helsinki researcher Pauli Paasonen, who led the study.
Scientists, according to the Rockville, MD-based Science Daily, had known that some aerosols — particles that float in the atmosphere — cool the climate as they reflect sunlight and form cloud droplets, which reflect sunlight efficiently. Aerosol particles come from many sources, including human emissions. But the effect of so-called biogenic aerosol — particulate matter that originates from plants — had been less well understood. Plants release gases that, after atmospheric oxidation, tend to stick to aerosol particles, growing them into the larger-sized particles that reflect sunlight and also serve as the basis for cloud droplets.
The new study showed that as temperatures warm and plants consequently release more of these gases, the concentrations of particles active in cloud formation increase.
Everyone knows the scent of the forest,” says Ari Asmi, University of Helsinki researcher who also worked on the study. “That scent is made up of these gases.” While previous research had predicted the feedback effect, until now nobody had been able to prove its existence except for case studies limited to single sites and short time periods. The new study showed that the effect occurs over the long-term in continental size scales.