Schematic representation of the physical mechanisms of climate-induced carbon cycle changes in the Amazon rainforest region. Credit: NIES
The Amazon, often called the “lungs of the planet,” is the world’s largest rainforest and plays a crucial role in the global climate system due to its large carbon reservoir. While it is generally warm and humid year-round, ongoing climate change is threatening more frequent and severe droughts and extreme heat.
A study published in Nature Communications looks at future projections of the Amazon carbon cycle, focusing specifically on impacts induced by climate change.
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 study, the impacts of climate change are isolated from other factors such as land-use changes, including deforestation, and CO2 Effect of fertilization on photosynthesis. An advanced technique known as emergent constraints that helps reduce uncertainties in future predictions by using past observations is used.
The study shows that climate change could lead to warmer and drier conditions in the Amazon rainforest, reducing the Amazon carbon sink, or the uptake of carbon dioxide by plants. Lead author Dr Irina Melnikova, a research associate at NIES, said: “This is happening because global warming is accompanied by a phenomenon known as polar amplification, which is greater warming in the polar regions than in other regions.”
The horizontal axes represent past global surface air temperature trends (1980–2014) in °C per year. The vertical axes show future projections for the Amazon: (a) surface air temperature change (°C), (b) precipitation change (%), and (c) climate change-induced carbon sink (GtC per year) as estimated by CMIP6 models. Pearson correlation coefficients and p-values are shown at the bottom of each panel. The horizontal boxplots display the mean (white line), 17–83% range (box), and 5–95% range (horizontal bar) of observed global temperature trends from HadCRUT4 (light blue). The vertical boxplots provide the same information but for the raw CMIP6 models (black) and ranges constrained using observations (teal). The emerging constraint is estimated for 120–139 year averages under the 1% CO2 scenario and for 2072–2091 under the SSP5-8.5 scenario, both corresponding to an inter-model average of 4.4 °C warming above pre-industrial levels. The figure is adapted from Figures 2 and S11 of Melnikova et al. (2024). Credit: NIES
This phenomenon causes a northward shift of the Intertropical Convergence Zone, a belt of tropical rains crucial to the Amazon’s climate. This shift would make the Amazon drier and warmer, reducing the rainforest’s ability to absorb carbon dioxide through photosynthesis while increasing carbon dioxide emissions from plants and soil respiration. Combined with the increased risk of droughts and fires in hotter and drier conditions, this would result in a net loss of carbon from the rainforest.
The new study also finds that Earth system models, which estimate past trends in global temperature increases, are more likely to predict a warmer and drier Amazon under a high-emissions scenario than other models. The study concludes that models that can reproduce past trends in global warming are more reliable in predicting the future carbon sink of the Amazon induced by climate change.
“By refining our projections with emerging constraints, we can provide more accurate predictions of future climate impacts, which are essential for informed policymaking,” Melnikova said.
This research successfully reduces uncertainties in predicting the Amazon’s response to climate change, improving our understanding and highlighting the critical role of accurate climate models in shaping future conservation strategies and global climate policies.
The results also reveal the possibility that further warming could trigger large-scale atmospheric circulation changes, leading to a drier and warmer Amazon climate and increased carbon emissions from the rainforest.
The authors warn: “While our study provides insight into the future of the Amazon, it also highlights the urgency of mitigating climate change to avoid worst-case scenarios. The fate of the Amazon is not just a regional concern, but a global one.”
More information:
Irina Melnikova et al., Emerging constraints on future climate change-induced carbon loss in the Amazon using past global warming trends, Nature Communications (2024). DOI: 10.1038/s41467-024-51474-8
Provided by the National Institute for Environmental Studies
Quote:Study finds future climate change could reduce Amazon rainforest’s ability to act as carbon sink (2024, September 19) retrieved September 19, 2024, from
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