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The basic elements of the carbon cycle have been incorrectly estimated

The basic elements of the carbon cycle have been incorrectly estimated

Some of the central mechanisms of the carbon cycle were shown to have been incorrectly estimated, which called for a review of the detailed representation of the latter in climate models. At least that’s what a study published in the scientific journal Nature Communications This is April 1.

Like the water cycle, the carbon cycle is central to climate dynamics. By determining the way carbon circulates through the various components of the climate system, it quantifies the global warming effect and its changes over multiple time scales. It also regulates the percentage of carbon dioxide and methane emissions that accumulate in the atmosphere.

Between photosynthesis and respiration, an unbalanced balance

The quality of climate projections depends on how accurately we understand this cycle. However, recent work has shown that estimates of certain basic quantities, such as the amount absorbed and released by vegetation or soil, were incoherent and did not make it possible to draw up a balance sheet on a global scale. In other words, the latter is unbalanced and A certain amount of carbon is missing in the balance.

According to the data typically used, the primary production provided by photosynthesis is 120 Pg (petagrams) of carbon, which means an emission of approximately 65 Pg by soil respiration. However, the observations reviewed by the researchers give soil respiration closer to 95 Pg, which means the initial production is about 150 Pg. For any quantitative study, these differences can be a problem.

Schematic representation of the carbon cycle. Reservoirs are supplied by billions of tons of carbon and flows by billions of tons of carbon annually. In black, pre-industrial values ​​and in red, the disturbances added by human activities at the beginning of the twenty-first century. Credits: IPCC.

Either the amount of carbon that plants take out of the atmosphere is wrong, or the amount of carbon that plants leave the soil is wrong wrong – wrong – wrong ,” according to Meredith Steele, co-author of the study. We don’t question the solid science of climate changebut we should be able to account for all the carbon in an ecosystem which we currently can’t She adds that Ecosystem response models to climate change need updating “.

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The carbon cycle is well understood, but some of its points remain to be clarified

While the first data is based on satellite estimates that may underestimate primary production, the second comes from downscaling techniques that may, on the contrary, overestimate emissions from soil. So the researchers’ goal now is to find out what’s wrong and to improve the representation of the carbon cycle in climate and ecosystem models.

Photosynthesis and respiration are the driving forces of the carbon cycle, but it is difficult to measure the net annual sum of each on a global scale says Lisa Welbe, a researcher who was not involved in the study. “ The authors’ attempts to reconcile global estimates from different societies show us that they are not entirely consistent and that there is more to learn about these central processes of our planet. “.