Estimates of the carbon cycle - vital to predicting climate change - are incorrect, new researchers show
Date:
April 1, 2022
Source:
Virginia Tech
Summary:
Researchers have discovered that key parts of the global carbon
cycle used to track movement of carbon dioxide in the environment
are not correct, which could significantly alter conventional carbon
cycle models. This finding has the potential to change predictions
for climate change, though it is unclear at this juncture if the
mismatch will result in more or less carbon dioxide being accounted
for in the environment.
FULL STORY ========================================================================== Virginia Tech researchers, in collaboration with Pacific Northwest
National Laboratory, have discovered that key parts of the global carbon
cycle used to track movement of carbon dioxide in the environment are not correct, which could significantly alter conventional carbon cycle models.
==========================================================================
The estimate of how much carbon dioxide plants pull from the atmosphere is critical to accurately monitor and predict the amount of climate-changing gasses in the atmosphere. This finding has the potential to change
predictions for climate change, though it is unclear at this juncture if
the mismatch will result in more or less carbon dioxide being accounted
for in the environment.
"Either the amount of carbon coming out of the atmosphere from the
plants is wrong or the amount coming out of the soil is wrong," said
Meredith Steele, an assistant professor in the School of Plant and Environmental Sciences in the College of Agriculture and Life Sciences,
whose Ph.D. student at the time, Jinshi Jian, led the research team. The findings are to be published Friday in Nature Communications.
"We are not challenging the well-established climate change science,
but we should be able to account for all carbon in the ecosystem and
currently cannot," she said. "What we found is that the models of the ecosystem's response to climate change need updating." Jian and Steele's
work focuses on carbon cycling and how plants and soil remove and return
carbon dioxide in the atmosphere.
To understand how carbon affects the ecosystems on Earth, it's important
to know exactly where all the carbon is going. This process, called carbon accounting, says how much carbon is going where, how much is in each of
Earth's carbon pools of the oceans, atmosphere, land, and living things.
==========================================================================
For decades, researchers have been trying to get an accurate accounting
of where our carbon is and where it is going. Virginia Tech and Pacific Northwest National Laboratory researchers focused on the carbon dioxide
that gets drawn out of the atmosphere by plants through photosynthesis.
When animals eat plants, the carbon moves into the terrestrial
ecosystem. It then moves into the soil or to animals. And a large amount
of carbon is also exhaled -- or respirated -- back into the atmosphere.
This carbon dioxide that's coming in and going out is essential for
balancing the amount of carbon in the atmosphere, which contributes to
climate change and storing carbon long-term.
However, Virginia Tech researchers discovered that when using the accepted numbers for soil respiration, that number in the carbon cycling models
is no longer balanced.
"Photosynthesis and respiration are the driving forces of the carbon
cycle, however the total annual sum of each of these at the global scale
has been elusive to measure," said Lisa Welp, an associate professor of
earth, atmospheric, and planetary sciences at Purdue University, who is familiar with the work but was not part of the research. "The authors'
attempts to reconcile these global estimates from different communities
show us that they are not entirely self-consistent and there is more
to learn about these fundamental processes on the planet." What Jian
and Steele, along with the rest of the team, found is that by using the
gross primary productivity of carbon dioxide's accepted number of 120
petagrams -- each petagram is a billion metric tons -- the amount of
carbon coming out through soil respiration should be in the neighborhood
of 65 petagrams.
==========================================================================
By analyzing multiple fluxes, the amount of carbon exchanged between
Earth's carbon pools of the oceans, atmosphere, land, and living things,
the researchers discovered that the amount of carbon soil respiration
coming out of the soil is about 95 petagrams. The gross primary
productivity should be around 147. For scale, the difference between
the currently accepted amount of 120 petagrams and this is estimate is
about three times the 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 be underestimating gross
primary production. The other is the upscaling of soil respiration measurements, which could be overestimating the amount of carbon returned
to the atmosphere.
Whether this misestimate 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 for the research is to determine which part of the global
carbon cycling model is being under or overestimated.
By having accurate accounting of the carbon and where it is in the
ecosystem, better predictions and models will be possible to accurately
judge these ecosystems' response to climate change, said Jian, who began
this research as a Ph.D. 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 carbon cycling and provide
better predictions of what the climate will look like in the future."
As Steele's first Ph.D. student at Virginia Tech, a portion of Steele's
startup fund went to support Jian's graduate research. Jian, fascinated
with data science, databases, and soil respiration, was working on another
part of his dissertation when he stumbled across something that didn't
quite add up.
Jian was researching how to take small, localized carbon measurements
from across the globe. While researching this, Jian discovered that
the best estimates didn't match up if all the fluxes of global carbon accounting were put together.
The research was funded by Steele's startup fund from the College of Agriculture and Life Sciences at Virginia Tech and further supported by
Pacific Northwest National Laboratory.
========================================================================== Story Source: Materials provided by Virginia_Tech. Original written by
Max Esterhuizen. Note: Content may be edited for style and length.
========================================================================== Journal Reference:
1. Jinshi Jian, Vanessa Bailey, Kalyn Dorheim, Alexandra G. Konings,
Dalei
Hao, Alexey N. Shiklomanov, Abigail Snyder, Meredith Steele,
Munemasa Teramoto, Rodrigo Vargas, Ben Bond-Lamberty. Historically
inconsistent productivity and respiration fluxes in the global
terrestrial carbon cycle. Nature Communications, 2022; 13 (1) DOI:
10.1038/s41467-022-29391- 5 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/04/220401094830.htm
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