Tropical rainforests absorb significantly less CO? from the atmosphere during periods of water scarcity, a feedback effect that has not been accounted for in most climate models. Over the past six years, land ecosystems, primarily plants through photosynthesis, have absorbed about one-third of human-made CO? emissions. However, whether this natural carbon sink will continue to absorb similar amounts of CO? from the Earth’s atmosphere in the coming years is one of the essential questions in climate research. Due to the various feedbacks that affect the Earth’s climate system, predicting this is complex. Feedbacks are processes caused by global warming that either mitigate or exacerbate climate change. Carbon-climate feedbacks, in particular, are difficult to measure and model, making them a significant uncertainty factor in climate models.
Scientists from the Swiss Federal Institute of Technology in Zurich (ETH Zurich) have published a study in the journal Nature, revealing that land ecosystems are more vulnerable to climate change than previously thought. The researchers found that drought periods in the last 60 years have significantly affected the carbon cycle in the tropics, with plants in rainforests absorbing significantly less CO? from the air during dry periods than previously assumed by common climate models. The study also investigated whether there is a correlation between water and CO? growth rates. According to the study’s results, the coupling between water availability in the tropics and CO? growth rates has increased significantly from 1989 to 2018 compared to 1960 to 1989. Thus, water scarcity in the tropics is becoming a limiting factor in the annual carbon cycle.
The vulnerability of the tropical carbon sink due to water scarcity is a significant uncertainty factor in climate models. The researchers’ findings suggest that the carbon sink of land ecosystems may decrease significantly earlier than previously thought, making it even more challenging to predict the Earth’s future climate. The study highlights the importance of considering feedback effects in climate models and the need for further research to better understand the complex interactions between the Earth’s climate system and the carbon cycle.
