In developing their approach, a team led by Daniel Hayes of the Department of Energy's ORNL took advantage of inventory records from the United States, Canada and Mexico that track changes in the amount of carbon in various reservoirs such as plants, soils and wood.
From these data, they made estimates of the current rate of atmospheric carbon dioxide sequestration over North America. This allowed researchers to calculate the state of the science in determining North America's carbon balance.
"Our results highlight both consistencies and mismatches among methods for quantifying sources and sinks of CO2 at sub-national scales and across different sectors such as forest, crop and other lands," Hayes said. "Depending on the approach, estimates suggest that the land-based sink offsets approximately 20 to 50 percent of total continental fossil fuel emissions."
The researchers noted that land and ocean sinks – which are sequestering carbon about equal amounts of carbon globally – are neither permanent nor fixed. Whether they continue to operate is a research question with critical implications. Hayes and colleagues found that much of the current carbon sequestration in North America is associated with the forest sector in the Northwest and Southeast.
"North American land ecosystems are thought to act as a relatively large sink for atmospheric CO2 , but both its current magnitude and response of this sink to future conditions are highly uncertain," Hayes said. The role played by North America is considerable as it may be responsible for up to a third of the combined global land and ocean sink of atmospheric CO2.
That ability to sequester carbon, however, may change given the influences of drought, wildfires and insect outbreaks that lead to carbon losses.
At odds in the carbon balance equation are the two most common assessment approaches – based on either top-down or bottom-up perspectives. From the top-down perspective, atmospheric models typically estimate much greater sink strength than bottom-up, or land ecosystem models. The inventory-based estimate is lower still than the average land model.
Each approach has strengths and weaknesses, and they all have substantial uncertainties. Modeling approaches are the primary tool available for making climate projections, but these rely on a large number of complicated and often poorly understood processes. Models are mainly based on physical, chemical and biological principles whereas inventories can track things like the movement of carbon in food and wood products that are influenced by social and economic factors.
Inventory methods like those used for this study have the benefit of extensive and repeated measurements yet there are many processes thought to be important that go unmeasured.
"You can't measure everything everywhere all of the time, especially in the future," Hayes said, "so we need models to fill in the gaps."
Scientists continue research to address knowledge gaps and uncertainties in each of these approaches.
"Ultimately, confidence in our ability to understand and predict the role of the North America carbon cycle in the global climate system will increase as new estimates from these different approaches begin to more closely converge and are combined in more fully integrated monitoring systems," Hayes said.
While there is still a huge range in estimates of CO2 sources and sinks, this paper, published today in the journal Global Change Biology, represents a major step toward reconciliation of the global carbon cycle. This could be especially relevant to policymakers.
"Efforts to establish atmospheric stabilization targets for CO2 emissions need accurate and reliable estimates of the global carbon budget," Hayes said.
The paper, titled "Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmosphere inversions, and a new approach for estimating net ecosystem exchange from inventory-based data," is available here: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2486.2011.02627.x/abstract
Co-authors from ORNL are Yaxing Wei, Mac Post and Robert Cook. Other authors include scientists from Oregon State University; the Canadian Forest Service; the U.S. Geological Survey; Pacific Northwest National Laboratory; the USDA Forest Service; El Colegio de la Frontera Sur, Mexico; Agriculture and Agri-Food Canada; and the National Oceanic and Atmospheric Administration.
This research was supported by multiple sources, including DOE's Office of Science, a Department of Agriculture grant and NASA's New Investigator Program and the Terrestrial Ecology Program. UT-Battelle manages ORNL for DOE's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov/
Ron Walli | EurekAlert!
Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen
A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
25.09.2017 | Physics and Astronomy
25.09.2017 | Trade Fair News
25.09.2017 | Physics and Astronomy