The terrestrial ecosystems sequester nearly one-quarter of the CO₂ emissions from human activities each year through photosynthesis, playing a key role in mitigating global warming. However, with the increasing frequency and intensity of warm extremes, the CO₂ sequestration capacity of terrestrial ecosystems has been challenged.

In a recent study published in Nature Ecology & Evolution, a research team led by Prof. LUO Geping from the Xinjiang Institute of Ecology and Geography (XIEG) of the Chinese Academy of Sciences investigated the impact of global warm extremes on the carbon sequestration capacity of terrestrial ecosystems.

Combining carbon flux data simulated by atmospheric CO₂ inversions, Earth system models, machine learning models, and global meteorological data as well as reanalysis data, researchers assessed the evolution patterns of global warm extremes from 1981 to 2020.

They found that global warm extremes have become more frequent and intense with a growth rate of 0.82 days per year and an increase of 0.023°C per year.

“Compared to the frequency of warm extremes, the intensity of warm extremes was found to have a stronger weakening effect on the carbon sequestration capacity of terrestrial ecosystems,” said YUAN Xiuliang, first author of this study. This weakening was found to be primarily attributed to a significant reduction in gross primary productivity relative to terrestrial ecosystem respiration.

Besides, researchers found that the current Earth system models are not able to effectively simulate the response of vegetation to warm extremes, resulting in an overestimation of carbon dioxide sequestration. Therefore, there is an urgent need to enhance the modeling capability of Earth system models.

As the frequency and intensity of warm extremes continue to increase, the proportion of CO₂ absorbed by terrestrial ecosystems from human activities may become less and less, posing greater challenges,” YUAN added.