Climate change

Carbon cycle estimates – key to predicting climate change – are incorrect, Virginia Tech researchers show | VTX

Virginia Tech researchers, in collaboration with the Pacific Northwest National Laboratory, have discovered that key elements of the global carbon cycle used to track the movement of carbon dioxide through the environment are not correct, which could significantly alter the conventional models of the carbon cycle.

Estimating the amount of carbon dioxide that plants extract from the atmosphere is essential to accurately monitoring and predicting the amount of climate-altering gases in the atmosphere. This discovery has the potential to alter predictions of climate change, although it is unclear at this stage whether the mismatch will lead to more or less carbon dioxide in the environment.

“Either the amount of carbon leaving the atmosphere of plants is wrong, or the amount leaving the soil is wrong,” said Meredith Steele, assistant professor at the School of Plant and Environmental Sciences in the College of Agriculture and Life Sciences, including the doctorate. student at the time, Jinshi Jian, led the research team. The findings were published Friday in Nature Communication.

“We don’t question the well-established science of climate change, but we should be able to account for all the carbon in the ecosystem and we currently cannot,” she said. “What we found is that models of ecosystem response to climate change need to be updated.”

Jian and Steele’s work focuses on the carbon cycle and how plants and soil remove and return carbon dioxide to the atmosphere.

To understand how carbon affects ecosystems on Earth, it is important to know exactly where all the carbon goes. This process, called carbon accounting, tells how much carbon goes where, how much is in each of Earth’s carbon pools of oceans, atmosphere, land, and living things.

For decades, researchers have tried to get an accurate accounting of where our carbon is and where it is going. The Virginia Tech and Pacific Northwest National Laboratory researchers focused on the carbon dioxide that is removed from the atmosphere by plants through photosynthesis.

When animals eat plants, carbon moves through the earth’s ecosystem. It then moves into the ground or towards animals. And a lot of carbon is also exhaled – or breathed in – into the atmosphere.

This carbon dioxide moving in and out is essential for balancing the amount of carbon in the atmosphere, which contributes to climate change and long-term carbon storage.

However, Virginia Tech researchers found that by using accepted numbers for soil respiration, this number in carbon cycle models is no longer balanced.

“Photosynthesis and respiration are the driving forces of the carbon cycle, but the total annual sum of each on a global scale has been difficult to measure,” said Lisa Welp, associate professor of Earth sciences, of the atmosphere and the planets at Purdue. University, which knows about the work but was not involved in the research. “The authors’ attempts to reconcile these global estimates from different communities show us that they are not entirely consistent and that there is more to learn about these fundamental processes on the planet.”

What Jian and Steele, along with the rest of the team, discovered was that using the gross primary productivity of the accepted number of 120 petagrams of carbon dioxide – each petagram is a billion metric tons – the amount of carbon released through soil respiration should be around 65 petagrams.

By analyzing multiple fluxes, the amount of carbon exchanged between the terrestrial carbon pools of the oceans, atmosphere, land and living things, the researchers found that the amount of soil respiration of carbon leaving the soil is of about 95 petagrams. Gross primary productivity is projected to be around 147. For scale, the difference between the currently accepted amount of 120 petagrams and this estimate is around three times global fossil fuel emissions each year.

According to the researchers, there are two possibilities for this. The first is that the remote sensing approach may underestimate gross primary production. The other is the scaling of measurements of soil respiration, which could overestimate the amount of carbon being returned to the atmosphere. Whether this flawed estimate is a positive or negative thing for the scientifically proven challenge of climate change is what needs to be examined next, Steele said.

The next step in the research is to determine which part of the global carbon cycle model is underestimated or overestimated.

By having an accurate accounting of carbon and its location in the ecosystem, better predictions and models will be possible to accurately judge the response of these ecosystems to climate change, said Jian, who started this research as a doctoral student. a student at Virginia Tech and is now at Northwest A&F University in China.

“If we think back to how the world was when we were young, the climate has changed,” Jian said. “We have more extreme weather events. This study should improve the models we used for the carbon cycle and provide better predictions of what the climate will look like in the future.

As Steele’s first doctorate. A student at Virginia Tech, part of Steele’s start-up fund went to support Jian’s graduate research. Jian, fascinated by data science, databases, and soil breathing, was working on another part of his thesis when he came across something that didn’t quite fit.

Jian was researching how to take small, localized measurements of carbon around the world. During his research, Jian discovered that the best estimates did not add up if all the flows from the global carbon account were lumped together.

The research was funded by Steele’s start-up fund from Virginia Tech’s College of Agriculture and Life Sciences and supported by Pacific Northwest National Laboratory.