Study finds future climate change could reduce the Amazon rainforest’s ability to absorb carbon

The Amazon is the world’s largest tropical forest and is often referred to as the “lungs of the Earth.” It plays a vital role in the Earth’s climate system due to its vast carbon stores. Normally it experiences warm and humid conditions all year round, but as climate change continues it is at risk of more frequent and severe droughts and extreme heat.

A study published in Nature Communications takes a closer look at future projections for the Amazon’s carbon cycle, with a particular focus on the impacts of climate change.

The scientists are using the latest generation of Earth system models from the Coupled Model Intercomparison Project, which contributed to the IPCC’s Sixth Assessment Report.

In the research framework, the impacts of climate change are isolated from other factors such as land use change, including deforestation, and the impact of carbon dioxide fertilization on photosynthesis. An advanced technique called Emergent Constraints is employed, which allows using past observations to reduce the uncertainty of future projections.

The study shows that future climate change could make the Amazon rainforest hotter and drier, which could result in a decrease in the Amazon’s carbon sink – the absorption of carbon dioxide by plants. “This happens because global warming is accompanied by a phenomenon called polar amplification, where the poles warm more than other regions,” said lead author Dr Irina Melnikova, a researcher at the National Institute for Environmental Studies.

This would shift the Intertropical Convergence Zone, a crucial rainforest region for the Amazon climate, northward, making the Amazon drier and warmer and reducing its ability to absorb carbon dioxide through photosynthesis while increasing carbon dioxide emissions through plant and soil respiration. Combined with a hotter, drier climate and increased risk of drought and fires, this would lead to a net loss of carbon from the rainforest.

The new study also finds that Earth system models that predict past global temperature trends are more likely to predict a hotter and drier Amazon under high emissions scenarios than other models. The study concludes that models that can reproduce past observed global warming trends are more reliable in predicting future Amazon carbon sinks from climate change.

“Refining our projections to take into account new constraints will allow us to more accurately forecast future climate impacts, which is essential for informed policymaking,” Melnikova said.

This study successfully reduced the uncertainty in predicting the Amazon’s response to climate change, improving our understanding and highlighting the important role that accurate climate models will play in shaping future conservation strategies and global climate policy.

The study also finds that further warming could lead to large-scale changes in atmospheric circulation, making the Amazon’s climate drier and hotter and increasing carbon emissions from the rainforest.

The authors warn: “While our study provides a more nuanced understanding of the Amazon’s future, it also highlights the urgency of mitigating climate change to prevent the worst-case scenario. The fate of the Amazon is not just a regional issue, but a global one.”