How will a warming world impact the Earth’s ability to offset our carbon emissions?

Newswise — Washington, DC—As global temperatures rise owing to climate change, to what extent can we still rely on plants and soils to mitigate some of the harm we've caused by extracting carbon pollution from the air?

A recent study spearheaded by Carnegie's Wu Sun and Anna Michalak addresses this crucial inquiry through the implementation of an innovative strategy to deduce the temperature responsiveness of ecosystem respiration—an integral component in the equilibrium between carbon dioxide absorption and emission in terrestrial ecosystems. The outcomes of their research have been documented in the journal Nature Ecology & Evolution.

"At present, plants within the terrestrial biosphere provide us with a valuable 'complimentary service' by absorbing approximately 25% to 33% of global carbon emissions from the atmosphere," clarified Michalak. "However, as the planet undergoes warming, can they sustain this pace of carbon dioxide removal? This question holds immense significance in comprehending the trajectory of our climate and formulating effective strategies for climate mitigation and adaptation."

Photosynthesis, the mechanism through which plants, algae, and certain bacteria transform solar energy into sugars as a source of sustenance, necessitates the absorption of atmospheric carbon dioxide. This process takes place exclusively during daylight hours. However, throughout both day and night, these very organisms engage in respiration, similar to humans, thereby exhaling carbon dioxide.

Enhancing our ability to accurately measure the equilibrium between these two processes across all elements of land-based ecosystems—ranging from soil microorganisms to trees and all other components—and comprehending their responsiveness to warming is instrumental in refining scientists' models for predicting climate change scenarios. By achieving a deeper understanding of this balance, researchers can improve the accuracy and reliability of their projections concerning the impacts of climate change.

In recent times, scientists, including Joe Berry from Carnegie, have made significant advancements in measuring the quantity of carbon dioxide absorbed by plants during photosynthesis. These breakthrough approaches include utilizing satellite technology to monitor global photosynthetic activity and measuring the concentration of a trace gas called carbonyl sulfide in the atmosphere. These innovative methods provide valuable insights into the photosynthetic activity of plants on a global scale, aiding in our understanding of carbon uptake and its implications for the Earth's carbon cycle.

However, up until now, the development of comparable tools to monitor respiration across entire biomes or continents has remained a challenge. Consequently, respiration is often estimated indirectly by calculating the difference between photosynthesis and the overall carbon dioxide uptake. The lack of direct measurement tools for respiration at large scales has presented limitations in accurately quantifying this vital component of the carbon cycle.

Sun stated that their objective was to create a novel approach for deducing the impact of temperature variations on respiration across diverse ecosystems in North America. They emphasized the significance of this endeavor in improving climate change forecasts and guiding the development of mitigation strategies.

Michalak, Sun, and their team successfully devised a novel method to estimate the extent of respiration augmentation on a large scale in response to temperature rise. Their approach relied on measurements of atmospheric carbon dioxide concentrations obtained from a network of numerous monitoring stations situated throughout North America.

The research team made a significant discovery by analyzing atmospheric observations, which indicated that the temperature sensitivity of respiration is lower than what is commonly portrayed in state-of-the-art models. Furthermore, they identified variations in this sensitivity between forests and croplands. This study marks the first time that observational data at such a large scale has been used to constrain temperature sensitivities of respiration, as previous investigations primarily focused on much smaller land plots.

Sun highlighted the effectiveness of their approach, emphasizing that by utilizing measurements of atmospheric carbon dioxide concentrations from strategically located monitoring stations, they were able to gain insights into carbon fluxes across entire biomes in North America. This comprehensive understanding of respiration at a continental scale is crucial for assessing the impact of future warming on the biosphere's capacity to retain carbon. Sun emphasized the importance of such knowledge in addressing the implications of climate change.

To their astonishment, the researchers discovered that respiration exhibits a lower sensitivity to warming than previously assumed when examined on a biome or continental scale. However, they emphasize the need for caution, acknowledging that temperature sensitivity is merely one aspect of a multifaceted puzzle. The findings suggest that a comprehensive understanding of respiration and its relationship with temperature requires considering various other factors and complexities in the ecosystem.

Michalak emphasized the importance of understanding that while their research suggests North American ecosystems might possess a greater resilience to warming than previously thought based on smaller-scale studies, mitigating climate change requires urgent action. Michalak warned against relying solely on natural components of the global carbon cycle to address the issue and stressed the necessity of reducing human-induced carbon emissions as quickly as possible. They highlighted that the responsibility lies with humanity to halt the escalating consequences of climate change, likening it to stopping a runaway train.

The research team also included Xiangzhong Luo, Yao Zhang, and Trevor Keenan from the University of California Berkeley and Lawrence Berkeley National Laboratory. Yuanyuan Fang from the Bay Area Air Quality Management District, Yoichi P. Shiga from the Universities Space Research Association, and Joshua Fisher from Chapman University were also part of the team. Their collective expertise and collaboration contributed to the comprehensive analysis and findings of the study.