Overestimated nitrogen availability has led climate models to exaggerate how much plant growth can offset rising CO2 levels.
Rising levels of carbon dioxide in the atmosphere are a major driver of climate change. At the same time, higher CO2 concentrations can encourage plants to grow faster, which in turn can help slow warming by drawing more carbon out of the air.
This benefit, however, depends on whether plants have access to enough nitrogen. New research suggests that scientists have only recently gained a clearer picture of how much nitrogen is actually available.
As a result, the so-called “fertilizing effect” of CO2 on plant growth has been significantly overstated, according to a new study involving the University of Graz.
Natural nitrogen fixation was overstated
Plants can only use nitrogen after it has been converted into a usable form in the soil by microorganisms. This process, known as biological nitrogen fixation, takes place in both natural environments and agricultural systems. “While this process has been significantly overestimated in nature, it has increased by 75 percent over the past 20 years due to agriculture,” explains Bettina Weber, a biologist at the University of Graz, summarizing findings published earlier this year.
Building on those results, a new study shows that calculations used in some Earth System models have now been revised. These models are widely used to assess climate trends, including in the World Climate Report. The updated analysis, published in the scientific journal PNAS, concludes that earlier estimates of nitrogen fixation were too high.
Climate models revise nitrogen assumptions
The publication was led by Sian Kou-Giesbrecht from Simon Fraser University in Burnaby, Canada, as part of a working group on biological nitrogen fixation, of which Bettina Weber is a member. The working group is supported by the U.S. Geological Survey (USGS) John Wesley Powell Centre for Analysis and Synthesis.
“We compared different Earth System models with current nitrogen fixation values and found that they overestimate the nitrogen fixation rate on natural surfaces by about 50 percent,” Weber explains. Overall, this overestimation of biological nitrogen fixation leads to a reduction in the CO2 fertilization effect of about 11 percent.
Weber therefore advocates revising the Earth System models in order to better assess developments. “This is because gases such as nitrogen oxides and nitrous oxide are produced as part of the nitrogen cycle. These can be released into the atmosphere through conversion processes and alter or disrupt climate processes.”
Reference: “Overestimated natural biological nitrogen fixation translates to an exaggerated CO2 fertilization effect in Earth system models” by Sian Kou-Giesbrecht, Carla R. Reis Ely, Steven S. Perakis, Cory C. Cleveland, Duncan N. L. Menge, Sasha C. Reed, Benton N. Taylor, Sarah A. Batterman, Timothy E. Crews, Katherine A. Dynarski, Maga Gei, Michael J. Gundale, David F. Herridge, Sarah E. Jovan, Mark B. Peoples, Johannes Piipponen, Emilio Rodríguez-Caballero, Verity G. Salmon, Fiona M. Soper, Anika P. Staccone, Bettina Weber, Christopher A. Williams and Nina Wurzburger, 24 November 2025, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2514628122
S.K.-G. was supported by the Natural Sciences and Engineering Research Council of Canada’s Discovery Grant Program (RGPIN-2024-04188). V.G.S. is supported by United States Department of Energy Office of Science Biological and Environmental Research to UT-Battelle, LLC grant DE-AC05-00OR22725 and the NGEE-Arctic project.
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8 Comments
The logical conclusion of what to do about uncertainty regarding the math in this situation would seem to me to be that we need to do everything that’s possible to increase carbon segregation. Trying to create huge underground reservoirs of carbon dioxide deep underground in order to reduce the amount of carbon dioxide seems quite risky to me. There is little data available to use to predict how long it is likely to take for that carbon dioxide to start leaking out of the “storage areas”. I find the explanations of why a carbon dioxide pipeline makes sense to be an extremely short term strategy. Assuming that huge amounts of carbon dioxide can be permanently sequestered underground is just such a huge assumption that it really would make just as much sense to simply trust in God. While that sounds pious, it amounts to telling God that you think you have the right to do whatever you want, and if you pray, he will bail you out of anything. My understanding of God is that he’s kind of a tough love parent. If we burn down so many trees that the area doesn’t have trees anymore, God is unlikely to wave his wand and restore the forests. When ther is just enough carbon dioxide absorbed by the ocean that the coral reefs die, asking God to return tge ocean to the appropriate pH could make God decide that we need to learn how to do the right things. My biggest fear right now is that, like most of the prophets God has sent in the past, Trump and his ilk will convince too many people that knowing what to expect from the actions humans take means that scientists are evil, godless men and need to be punished if their predictions are accurate. There are people who worship profits while pretending to trust in God. Those people are quite willing to take a chance on ecological disaster in the next 50 years as long as they can reap record profits in the next 15 years.
Would there be rich people in the world if God didn’t want rich people to exist? Appealing to the scriptures or divine authority ends up being a case of presenting your personal interpretation of the nature of God, as derived reading from the scriptures. Disagreements between representatives of the various religions has resulted in the premature deaths of millions of people, often because of the disagreement of a single word, as in, “It depends on what the meaning of the word ‘is’ is.”
This article is being posted as…”science “? Anyone with an ability to read at a 12th grade level and an ability to critically think can do this : Read about the Cambrian period in prehistoric times where CO2 levels where at 4000+ ppm and plant life at that time. This article is based on junk science driven by politics.
Agreed. Anything to induce panic, fear, and condition people into accepting more control disguised as saving the planet.
Yes, the world thrived @ 0.2% atmospheric carbon, Dinos, cave men and women, etc – and suddenly it is down to 0.04% but where all plant life dies away at 0.02% carbon (slightly lower than present). We need climate alarmists to be sequestered before their contribution to killing off the whole world is successful.
Or perhaps someone can make large scale carbon producing terraforming generators and advertise specified stock portfolios for energy production and saving the world for the Oxygen producing plants and those of us who wish to continue breathing.
Maybe write Jim Cameron to submit his designs as he had imagery for such generators in his Aliens2 movie – so he might, in his elder years wake up and realize he’s been had by the propaganda.
“We compared different Earth System models with current nitrogen fixation values and found that they overestimate the nitrogen fixation rate on natural surfaces by about 50 percent,”
To paraphrase Galileo, “And yet the world continues to green.”
While the authors plead that their concern is that the General Circulation Models need to have accurate assessments of the sequestration of CO2, they only talk about terrestrial plants and their limitations resulting from available nitrogen. There is no mention of how photosynthetic marine organisms are impacted by their studies. Is the science settled? Or are they failing to present the whole picture?
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From everything I have read, water injection has benefits for internal combustion engines. However, “doubling the fuel mileage” isn’t entirely accurate because it doesn’t take into account the consumption of water and alcohol. That also is one of the downsides because gas stations didn’t carry the distilled water/alcohol mixtures necessary, and the engine didn’t run optimally if the mixture wasn’t injected; it was almost certainly going to run out on long trips.
The linked article remarks about the “astronomical price of gas.” The price of gasoline is mostly taxes, which aren’t going to go away because they maintain they roads.