Plant CO2 absorption increases by nearly one third in new global estimate

Plant CO2 absorption increases by nearly one third in new global estimate
by Clarence Oxford
Los Angeles CA (SPX) Oct 22, 2024
Plants worldwide are absorbing approximately 31% more carbon dioxide (CO2) than previously believed, according to new research by scientists. The study, published in *Nature*, is expected to improve climate modeling and emphasizes the importance of natural carbon absorption in reducing greenhouse gases.

The process of removing CO2 through plant photosynthesis, known as Terrestrial Gross Primary Production (GPP), is the largest carbon exchange between land and the atmosphere. GPP is measured in petagrams of carbon per year, with one petagram equaling 1 billion metric tons. This is roughly equivalent to the annual CO2 emissions from 238 million gas-powered cars.

Researchers from Cornell University, in collaboration with Oak Ridge National Laboratory (ORNL), applied new models to estimate GPP at 157 petagrams of carbon per year, significantly higher than the previous estimate of 120 petagrams established 40 years ago. Their findings are detailed in the paper "Terrestrial Photosynthesis Inferred from Plant Carbonyl Sulfide Uptake."

The team tracked carbonyl sulfide (OCS), a chemical compound that moves through plant leaves similarly to CO2. OCS serves as a reliable proxy for measuring photosynthesis, making it easier to estimate global GPP accurately. The new model was developed using data from several sources, including ORNL's LeafWeb database, which supports carbon cycle research.

A crucial aspect of the new estimate is the improved understanding of mesophyll diffusion-the process through which OCS and CO2 travel from the leaf surface to chloroplasts for carbon fixation. This understanding is vital for assessing photosynthetic efficiency and predicting how plants might respond to environmental changes.

Co-author Lianhong Gu, a distinguished scientist at ORNL, noted that the original GPP estimate of 120 petagrams per year, established in the 1980s, remained in use for decades. "It's important that we get a good handle on global GPP since that initial land carbon uptake affects the rest of our representations of Earth's carbon cycle," Gu said.

The new estimates particularly highlight tropical rainforests as a more significant carbon sink than previously thought. This finding, supported by ground data, suggests that rainforests play a larger role in natural carbon sequestration compared to earlier satellite-based measurements.

Peter Thornton, a Corporate Fellow at ORNL, emphasized the importance of refining global GPP estimates for improving climate predictions. "Nailing down our estimates of GPP with reliable global-scale observations is a critical step in improving our predictions of future CO2 in the atmosphere, and the consequences for global climate," Thornton said.

This research will inform the development of next-generation models, especially those focused on tropical forests, to reduce uncertainties in predictions related to the global carbon cycle.

Research Report:Terrestrial photosynthesis inferred from plant carbonyl sulfide uptake