Feuchtigkeit moduliert die Reaktionen des Klima-Kohlenstoff-Zyklus

Die Umsatzzeiten des Kohlenstoffs an Land bestimmen die Auswirkungen von Klimaveränderungen auf die Landoberfläche. Die Temperaturempfindlichkeit des Kohlenstoffumsatzes zu verstehen und zu quantifizieren ist daher im Zusammenhang mit dem Klimawandel von entscheidender Bedeutung. Eine in Nature Geoscience veröffentlichte Studie belegt nun, dass die Feuchtebedingungen die vermeintliche Temperaturempfindlichkeit der Kohlenstoffumsatzzeiten stark verändern. Das internationale Team, angeführt von Nuno Carvalhais und Naixin Fan vom Max-Planck-Institut für Biogeochemie, zeigt, dass neben der Temperatur auch hydrometeorologische Faktoren die Reaktion der Kohlenstoffumsatzzeiten auf langfristige Klimaschwankungen erheblich beeinfussen.

Eine Übersetzung folgt in Kürze.

Understanding and quantifying the sensitivity of carbon cycle to long-term climate change is paramount to better predict how the functioning of terrestrial ecosystem will change in the context of global warming. However, the carbon cycle’s response to temperature is subject to substantial uncertainty. This study addressed the role of confounding factors to determine the magnitude of the temperature-carbon cycle feedback dynamics in Earth system sciences.

In a new study published in Nature Geoscience, the research team investigated the role of hyd-rometeorological factors (H-factors) in shaping the spatial variability of carbon turnover times from global to latitudinal scales. By using an observation-based ensemble of global carbon turno-ver estimations at large scales and  estimates derived from in-situ measurements at more than 200 geographical sites. They provide a full investigation on the responses of carbon turnover to the spatial gradient of temperature as well as well as H-factors at different scales.

“It is surprising that hydrometeorology is almost equally important as temperature in shaping the spatial pattern of ecosystem carbon turnover”, says Naixin Fan, first author of the study and a doctoral candidate at the Max Planck Institute of Biogeochemistry and now a researcher in the Department of Photogrammetry and Remote Sensing at the Technical University Dresden. There is a general consensus among previous studies that temperature is the main driver of terrestrial carbon turnover. However, the new study shows that H-factors can explain 40% of the global variability in contrast to the 60% that can be explained by temperature alone. This provides strong evidence that hydrometeorological and hydrological processes are also important. “It is known that the processes that shape carbon turnover, on land are simultaneously affected by mul-tiple environmental factors. This research provides a perspective on how balanced the role of temperature is to that of moisture, argues for comprehensive and multi-variate approaches in de-termining the sensitivity of carbon cycle to climate change”, says Dr. Carvalhais. 

The response of terrestrial carbon turnover to climate is one of the most uncertain processes that is simulated in the current Earth System Models (ESMs). The projected changes in carbon turno-ver times among different ESMs are characterized by a large spread in the magnitude, even so-metimes with opposite sign. This study suggests that carbon turnover process may strongly de-pend on changes in the hydrometeorological or hydrological cycle. The estimated values of tem-perature sensitivity of carbon turnover with the influence of different climate variables can also provide insight and even improve the simulation of feedback between the carbon cycle and the climate.         

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