With images of the fires in Australia burning your eyes on every news site, it is not a surprise that environmental scientists are calling for an update to the goals laid out in the Paris agreement. The recent IPCC report declared the need to improve land-use management, harping on the important role that forests and grasslands play in carbon uptake.
According to experts, roughly 30% of the carbon dioxide that humans emit (principally from fossil fuels and grasslands) are absorbed by terrestrial carbon sinks. In order to meet the Paris agreement goals, we must put greater emphasis on investment in more effective land-use options. To do so intelligently, the net carbon dioxide flux must be considered – which is exactly what a recent study published in Global Change Biology aimed to do.
“It is important to understand the best science-based estimate of where atmospheric CO2 is fixed in terrestrial ecosystems today, and our study makes a significant step in that direction," says Masayuki Kondo, an Assistant Professor at the Center for Environmental Remote Sensing, Chiba University. "There is an urgent need of how much carbon mitigation is required to achieve the temperature targets of the Paris agreement, but we still had a wide spread of estimates on how much CO2 the world terrestrial ecosystems are removing," says Kondo.
According to Science Daily, the net CO2 flux refers to the sum of CO2 absorption by photosynthesis (-) and CO2 emissions (+) from respiration, decomposition of soil organic matter, forest fires, and land-use changes like deforestation and forest conversion to farmland. As you can imagine, accurately calculating this flux is quite a scientific hurdle.
One way of measuring net CO2 flux uses terrestrial biosphere models to simulate the ongoing processes in the atmosphere and on Earth. "Up until now, scientists in various fields of earth science have proposed many kinds of methods to estimate net CO2 flux, including biosphere models and atmospheric inversions. These methods do not provide consistent results until we added the CO2 that is outgassed to the atmosphere by rivers and lakes to the biosphere models."
Adding these readings into the models was key to the findings from the new study, which reduced discrepancies in the Global Carbon Budgets from the IPCC Assessment Report over the last several years.
The team of researchers plans to continue this work in order to obtain even more precise net CO2 flux estimations. Kondo concludes, saying, "With the degree of accuracy that we achieved, we are getting confidence in how much CO2 the world terrestrial ecosystems are removing today. This is a good sign of our progress towards the goals of the Paris agreement. We need to continue working together with experts from various fields of research more than ever."