New Paper Shows Climate Models Underestimate CO2 Cycling By Plants

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Net primary productivity (NPP) describes how much carbon plants store through photosynthesis, a process we heavily rely on for absorbing man-made CO2 emissions and slowing down climate change. By combining measurements of radiocarbon produced by nuclear bomb tests with model simulations, new research reveals that existing models might be underestimating how much carbon plants store.

In a paper published in Science, findings show that most models used in the Coupled Model Intercomparison Project (CMIP) underestimate the radiocarbon accumulated in vegetation because they do not fully account for carbon stored in short-lived, non-woody plant tissues. Simulations by these models are used to inform assessments of climate change published by the Intergovernmental Panel on Climate Change (IPCC). Findings indicates that net primary productivity may be at least 80 petagrams of carbon per year, rather than the 43-76 petagrams predicted by models. This carbon is also likely to be more short-lived and vulnerable.

Dr Heather Graven at Imperial College London led the research team which included Agile Sprint research Professor Samar Khatiwala. In a news post published by the Department of Earth Sciences, Professor Khatiwala said, “This study highlights the pressing need to improve the models used to predict future climate change by calibrating them against measurements. Until recently this was thought to be unfeasible because of how time consuming these models are to run, but new research is bringing this goal closer to reality.”

Professor Khatiwala’s Sprint research is developing a scalable and robust algorithm to address the “spin-up” problem in Earth System Modelling, trying to solve how time consuming – and therefore expensive – these models are to run. Read more about this work in a recent paper published in Science Advances and on the Sprint research page

Read the paper in Science“Bomb radiocarbon evidence for strong global carbon uptake and turnover in terrestrial vegetation” (20 June 2024)