Two recent international studies have explored the relationship between Earth’s climate and the carbon cycle to investigate Earth’s deep breaths of carbon dioxide.
The two reports, to be published online by the journal Science, shed light on the amount of carbon that our planet is able to breathe in, so to speak, and the amount that it is breathing back out into the atmosphere.
Both studies will play a role in updating and improving climate models that show the relationship between the climate and the amount of carbon in the atmosphere, that we generate and that our planet can tolerate before it shifts.
The first study was conducted by Christian Beer from the Max Planck Institute for Biogeochemistry in Jena, Germany, along with colleagues from 10 other countries around the world, and looked at Earth’s Gross Primary Production, or GPP, which refers to the total amount of carbon dioxide that plants on the surface of the planet breathe in through photosynthesis each year.
“An understanding of the factors that control the GPP of various terrestrial ecosystems is important because we humans make use of many ecosystem services, such as wood, fiber, and food,” said Beer. “Additionally, such an understanding is important in the context of climate change as a consequence of carbon dioxide emissions from burning fossil fuels because vegetation greatly modulates the land-atmosphere exchanges of greenhouse gases, water, and carbon dioxide…”
The researchers found that Earth’s tropical forests are responsible for 34% of the carbon dioxide inhaled from the atmosphere, while the savannas account for 26%. Both figures look promising, but when you consider that savannas occupy twice as much surface area as the tropical forests do, the numbers start to look a little different.
The second study by Miguel Mahecha, also from the Max Planck Institute for Biogeochemistry, as well as an international team of researchers, settled a long-standing debate over the short term variations in air temperature and the effects they have on the exhalation of carbon dioxide back into the atmosphere.
“Our key finding is that the short-term temperature sensitivity of ecosystem respiration to air temperature is converging to a single, global value,” Mahecha said. “Contrary to previous studies, we show that the sensitivity of ecosystem respiration to temperature variations seems to be independent from external factors and constant across ecosystems. In other words, we found a general relationship between variation in temperature and ecosystem respiration… Our findings reconcile the apparent contradictions of modeling and field studies.”
Both studies used information gathered using the FLUXNET network, a global network of micrometeorological tower sites that measure the exchanges of carbon dioxide, water vapour and energy between the biosphere and the atmosphere.
As of the beginning of 2009 there were over 500 tower sites in continuous long-term operation across the face of our planet. Researchers use the tower sites to collect data on site vegetation, soil, hydrology and meteorological characteristics.