Billion Metric Tons Of Carbon Research Articles

Urbanization associated changes in biogeochemical cycles.

Urbanization associated changes in biogeochemical cycles.

Record-high CO2 emissions from boreal fires in 2021.

Extreme wildfires are becoming more common and increasingly affecting Earth's climate. Wildfires in boreal forests have attracted much less attention than those in tropical forests, although boreal forests are one of the most extensive biomes on Earth and are experiencing the fastest warming. We used a satellite-based atmospheric inversion system to monitor fire emissions in boreal forests. Wildfires are rapidly expanding into boreal forests with emerging warmer and drier fire seasons. Boreal fires, typically accounting for 10% of global fire carbon dioxide emissions, contributed 23% (0.48 billion metric tons of carbon) in 2021, by far the highest fraction since 2000. 2021 was an abnormal year because North American and Eurasian boreal forests synchronously experienced their greatest water deficit. Increasing numbers of extreme boreal fires and stronger climate-fire feedbacks challenge climate mitigation efforts.

Dissolved Organic Matter in the Global Ocean: A Primer.

Marine dissolved organic matter (DOM) holds ~660 billion metric tons of carbon, making it one of Earth’s major carbon reservoirs that is exchangeable with the atmosphere on annual to millennial time scales. The global ocean scale dynamics of the pool have become better illuminated over the past few decades, and those are very briefly described here. What is still far from understood is the dynamical control on this pool at the molecular level; in the case of this Special Issue, the role of microgels is poorly known. This manuscript provides the global context of a large pool of marine DOM upon which those missing insights can be built.

Getting to the Bottom of Trawling’s Carbon Emissions

A new model shows that bottom trawling, which stirs up marine sediments as weighted nets scrape the ocean floor, may be releasing more than a billion metric tons of carbon every year.

Effect of carbon content on sound speed and attenuation of sediments in seagrass meadows

Globally, seagrass-bearing sediments contain 19.9 billion metric tons of carbon (C), and account for 10% of all organic C buried in the ocean each year. Protection of these C stores is vital in mitigating climate change [Fourqurean, J. W., et al., Nature Geoscience 5, 505–509 (2012)]. Some sediment acoustic properties are sensitive to the presence of gas bubbles entrained in such C stores due to inherent anaerobic decomposition. Measurement of these properties could therefore provide a means to indirectly monitor C stores and overall seagrass meadow productivity. As a preliminary effort to investigate the relationship between C content and acoustic properties of seagrass-bearing sediments, cores were collected in the seagrass meadows of Lower Laguna Madre, Texas. Sound speed and attenuation from 100 kHz to 300 kHz were measured radially in 2-cm-depth increments. The cores were subsequently frozen, sliced along the same depth increments, and their C content estimated using an elemental analyzer. Acoustic properties were compared with C content along the depth of each core. The potential for sound speed and attenuation of seagrass-bearing sediments to be used as a metric for monitoring seagrass meadow productivity will be discussed. [Work supported by ONR and ARL:UT IR&D.]

Global agriculture and carbon trade-offs.

Feeding a growing and increasingly affluent world will require expanded agricultural production, which may require converting grasslands and forests into cropland. Such conversions can reduce carbon storage, habitat provision, and other ecosystem services, presenting difficult societal trade-offs. In this paper, we use spatially explicit data on agricultural productivity and carbon storage in a global analysis to find where agricultural extensification should occur to meet growing demand while minimizing carbon emissions from land use change. Selective extensification saves ∼ 6 billion metric tons of carbon compared with a business-as-usual approach, with a value of approximately $1 trillion (2012 US dollars) using recent estimates of the social cost of carbon. This type of spatially explicit geospatial analysis can be expanded to include other ecosystem services and other industries to analyze how to minimize conflicts between economic development and environmental sustainability.

Modeling challenges for predicting hydrologic response to degrading permafrost

The fate of the approximately 1,700 billion metric tons of carbon (Tarnocai et al. 2009) currently frozen in permafrost affected regions of the Arctic and subarctic is highly uncertain (IPCC 2007), primarily because of the potential for topographic evolution and resulting drainage network reorganization as permafrost degrades and massive ground ice contained in ice-rich permafrost soils melts. Computer modeling is a key tool in untangling these complex feedbacks to understand the evolution of the Arctic and subarctic landscapes and the potential feedbacks with the global climate system. Some of the challenges associated with modeling the hydrologic system in and around degrading permafrost are discussed in this essay. Modeling requirements depend very strongly on the spatial resolution of the model. Two different classes can be identified, depending on whether microtopography is explicitly resolved or incorporated into the model through a subgrid parameterization. The focus here is on the computational challenges associated with microtopography-resolving models using hydrologic response of polygon mires as an example. In such microtopography-resolving models, horizontal grid spacing on the order of 0.25mwould typically be required. Although highand low-centered ice wedge polygons have been identified as important controls on Arctic surface hydrology (e.g. Liljedahl et al. 2012) and evolution from lowto highcentered polygon landscapes is expected as Arctic temperatures increase (Jorgenson et al. 2006), as far as we are aware, there is no existing computer code that represents the full range of processes required to model the co-evolution of surface topography, active layer, and permafrost at the microtopography-resolving scale. For microtopography-resolving models of hydrology in permafrost landscapes, it is convenient to partition the large number of coupled processes into four critical sets: subsurface thermal/hydrology, surface thermal processes, mechanical deformation, and overland flow processes. However, it is important to recognize that the partitioning is somewhat arbitrary and that multiple tightly coupled processes exist within each set.

Detecting regional anthropogenic trends in ocean acidification against natural variability

Since the beginning of the Industrial Revolution humans have released ~500 billion metric tons of carbon to the atmosphere through fossil-fuel burning, cement production and land-use changes1, 2. About 30% has been taken up by the oceans3. The oceanic uptake of carbon dioxide leads to changes in marine carbonate chemistry resulting in a decrease of seawater pH and carbonate ion concentration, commonly referred to as ocean acidification. Ocean acidification is considered a major threat to calcifying organisms4, 5, 6. Detecting its magnitude and impacts on regional scales requires accurate knowledge of the level of natural variability of surface ocean carbonate ion concentrations on seasonal to annual timescales and beyond. Ocean observations are severely limited with respect to providing reliable estimates of the signal-to-noise ratio of human-induced trends in carbonate chemistry against natural factors. Using three Earth system models we show that the current anthropogenic trend in ocean acidification already exceeds the level of natural variability by up to 30 times on regional scales. Furthermore, it is demonstrated that the current rates of ocean acidification at monitoring sites in the Atlantic and Pacific oceans exceed those experienced during the last glacial termination by two orders of magnitude.

Biochar: Carbon Mitigation from the Ground Up

As multibillion-dollar projects intended to sequester carbon dioxide (CO2) in deep geologic storage continue to seek financial support, the fertile black soils in the Amazon basin suggest a cheaper, lower-tech route toward the same destination. Scattered patches of dark, charcoal-rich soil known as terra preta (Portuguese for “black earth”) are the inspiration for an international effort to explore how burying biomass-derived charcoal, or “biochar,” could boost soil fertility and transfer a sizeable amount from the atmosphere into safe storage in of CO2 topsoil. Although burial of biochar is just beginning to be tested in long-term, field-scale trials, studies of Amazonian terra preta show that charcoal can lock up carbon in the soil for centuries and improve soil fertility. Charcoal is made by heating wood or other organic material with a limited supply of oxygen (a process termed “pyrolysis”). The products of the pyrolysis process vary by the raw material used, burning time, and temperature, but in principle, volatile hydrocarbons and most of the oxygen and hydrogen in the biomass are burned or driven off, leaving carbon-enriched black solids with a structure that resists chemical and microbial degradation. Christoph Steiner, a research scientist at the University of Georgia, says the difference between charcoal and biochar lies primarily in the end use. “Charcoal is a fuel, and biochar has a nonfuel use that makes carbon sequestration feasible,” he explains. “Otherwise there is no difference between charcoal carbon and biochar carbon.” Charcoal is traditionally made by burning wood in pits or temporary structures, but modern pyrolysis equipment greatly reduces the air pollution associated with this practice. Gases emitted from pyrolysis can be captured to generate valuable products instead of being released as smoke. Some of the by-products can be condensed into “bio-oil,” a liquid that can be upgraded to fuels including biodiesel and synthesis gas. A portion of the noncondensable fraction is burned to heat the pyrolysis chamber, and the rest can provide heat or fuel an electric generator. Pyrolysis equipment now being developed at several public and private institutions typically operate at 350–700°C. In Golden, Colorado, Biochar Engineering Corporation is building portable $50,000 pyrolyzers that researchers will use to produce 1–2 tons of biochar per week. Company CEO Jim Fournier says the firm is planning larger units that could be trucked into position. Biomass is expensive to transport, he says, so pyrolysis units located near the source of the biomass are preferable to larger, centrally located facilities, even when the units reach commercial scale.

Selective Logging in the Brazilian Amazon

Amazon deforestation has been measured by remote sensing for three decades. In comparison, selective logging has been mostly invisible to satellites. We developed a large-scale, high-resolution, automated remote-sensing analysis of selective logging in the top five timber-producing states of the Brazilian Amazon. Logged areas ranged from 12,075 to 19,823 square kilometers per year (+/-14%) between 1999 and 2002, equivalent to 60 to 123% of previously reported deforestation area. Up to 1200 square kilometers per year of logging were observed on conservation lands. Each year, 27 million to 50 million cubic meters of wood were extracted, and a gross flux of approximately 0.1 billion metric tons of carbon was destined for release to the atmosphere by logging.

Impact of Humans on the Flux of Terrestrial Sediment to the Global Coastal Ocean

Here we provide global estimates of the seasonal flux of sediment, on a river-by-river basis, under modern and prehuman conditions. Humans have simultaneously increased the sediment transport by global rivers through soil erosion (by 2.3 +/- 0.6 billion metric tons per year), yet reduced the flux of sediment reaching the world's coasts (by 1.4 +/- 0.3 billion metric tons per year) because of retention within reservoirs. Over 100 billion metric tons of sediment and 1 to 3 billion metric tons of carbon are now sequestered in reservoirs constructed largely within the past 50 years. African and Asian rivers carry a greatly reduced sediment load; Indonesian rivers deliver much more sediment to coastal areas.

Potential world garbage and waste carbon sequestration

To offset the carbon dioxide released by fossil fuels, a proposed sequestration strategy relies on burying garbage and waste in landfills. This paper roughly estimates the current annual world supply of carbonaceous waste to be 35.5 billion metric tons and to contain about 18 billion metric tons of carbon. If landfills received all of this waste, sequestration of more than 5.6 billion metric tons of carbon seems theoretically possible—an amount well in excess of the 3.3 billion metric tons which the atmosphere is currently gaining.

8 Genetic, Molecular, and Morphological Analysis of Compound Leaf Development

Leaves, the plant organs responsible for capturing and converting most of the 170 billion metric tons of carbon fixed globally each year, can be broadly grouped into two morphological categories: simple and compound. Although simple-leaved species such as corn and Arabidopsis have traditionally been favored model systems for studying leaf development, recent years have seen an increase in genetic and molecular studies of compound leaf development. Two compound-leaved species in particular have emerged as model systems: tomato and pea. A variety of mutations which alter leaf morphology in these species have been described, and analyses of these mutations have allowed the construction of testable models of leaf development. Also, the knotted-like homeobox (KNOX) genes, which were originally discovered as regulators of meristem function, now appear to have a role in compound leaf development. In addition to the recent genetic and molecular analyses of tomato and pea, insight into the nature of compound leaf development may be gained through the study of (a) heteroblasty and heterophylly, phenomena in which a range of leaf forms can be produced by a single shoot, and (b) the evolutionary origins of compound leaves.

The role of phytoplankton photosynthesis in global biogeochemical cycles

Phytoplankton biomass in the world's oceans amounts to only ∽1-2% of the total global plant carbon, yet these organisms fix between 30 and 50 billion metric tons of carbon annually, which is about 40% of the total. On geological time scales there is profound evidence of the importance of phytoplankton photosynthesis in biogeochemical cycles. It is generally assumed that present phytoplankton productivity is in a quasi steady-state (on the time scale of decades). However, in a global context, the stability of oceanic photosynthetic processes is dependent on the physical circulation of the upper ocean and is therefore strongly influenced by the atmosphere. The net flux of atmospheric radiation is critical to determining the depth of the upper mixed layer and the vertical fluxes of nutrients. These latter two parameters are keys to determining the intensity, and spatial and temporal distributions of phytoplankton blooms. Atmospheric radiation budgets are not in steady-state. Driven largely by anthropogenic activities in the 20th century, increased levels of IR- absorbing gases such as CO2, CH4 and CFC's and NOx will potentially increase atmospheric temperatures on a global scale. The atmospheric radiation budget can affect phytoplankton photosynthesis directly and indirectly. Increased temperature differences between the continents and oceans have been implicated in higher wind stresses at the ocean margins. Increased wind speeds can lead to higher nutrient fluxes. Throughout most of the central oceans, nitrate concentrations are sub-micromolar and there is strong evidence that the quantum efficiency of Photosystem II is impaired by nutrient stress. Higher nutrient fluxes would lead to both an increase in phytoplankton biomass and higher biomass-specific rates of carbon fixation. However, in the center of the ocean gyres, increased radiative heating could reduce the vertical flux of nutrients to the euphotic zone, and hence lead to a reduction in phytoplankton carbon fixation. Increased desertification in terrestrial ecosystems can lead to increased aeolean loadings of essential micronutrients, such as iron. An increased flux of aeolean micronutrients could fertilize nutrient-replete areas of the open ocean with limiting trace elements, thereby stimulating photosynthetic rates. The factors which limit phytoplankton biomass and photosynthesis are discussed and examined with regard to potential changes in the Earth climate system which can lead the oceans away from steady-state. While it is difficult to confidently deduce changes in either phytoplankton biomass or photosynthetic rates on decadal time scales, time-series analysis of ocean transparency data suggest long-term trends have occurred in the North Pacific Ocean in the 20th century. However, calculations of net carbon uptake by the oceans resulting from phytoplankton photosynthesis suggest that without a supply of nutrients external to the ocean, carbon fixation in the open ocean is not presently a significant sink for excess atmospheric CO2.

Soil organic matter must be restored to near original levels

Abstract Burning of fossil fuels globally helps put 3 billion metric tons of carbon into the atmosphere per year more than is removed by all carbon sinks. By far the best use of that carbon would be to arrange sufficient extra plant growth and then transfer that plant growth into new stable soil organic matter. Twenty or more years of such effort would immensely improve the soils of the world. Any fraction of it would help decrease the threat of global greenhouse warming. A great worldwide goal should be to increase levels of soil organic matter levels considerably. It should be possible. The most important research relating to soil organic matter is perhaps yet to be done. Elucidation of the regulators involved in the build‐up and decomposition processes of various types of soil organic matter deserves high priority. It should be possible to develop technologies where the regulators can be managed and controlled for the beneficial purpose of increasing levels of soil organic matter. The role of calcium i...

Photovoltaics and materials science: helping to meet the environmental imperatives of clean air and climate change

Human activity is altering the composition of the atmosphere in unprecedented ways. Fossil fuel combustion, which currently releases 5.6 billion metric tons of carbon annually, in combination with deforestation, has increased atmospheric concentrations of carbon dioxide 25% above pre-industrial levels. Carbon dioxide and other greenhouse gases trap infrared radiation from the earth altering its thermal balance. While carbon dioxide is anticipated to contribute about one-half of human induced global warming, the world energy sector is responsible for an estimated 57% of future global warming when contributions from additional combustion related pollutants are included. In order to stabilize atmospheric concentrations of carbon dioxide even at current elevated levels, computer models suggest the need to reduce emission rates by approximately 75%. Present patterns of energy use are also contributing to major air pollution problems. An analysis of policy options shows that a combination of vastly improved energy efficiency strategies and carbon free energy production technologies are essential to simultaneously slow the rate of global warming and improve air quality. This paper summarizes current knowledge of the greenhouse effect and its consequences, and examines how photovoltaic electricity can contribute to atmospheric stabilization goals. Some specific examples and strategies will be given that may accelerate the rate at which photovoltaic technologies can penetrate the market. Should these strategies succeed, it will have majot implications for materials science including increased attention to pollution problems associated with the manufacture of many promising photovoltaic technologies.

Solar strategies for escaping the greenhouse heat trap

Abstract Human-induced global climate change poses an immense potential threat to our society, and a challenge to our ingenuity. Fossil fuel combustion, which currently releases 5.6 billion metric tons of carbon annually, in combination with deforestation, has increased atmospheric concentrations of carbon dioxide 25% above pre-industrial levels. Carbon dioxide is estimated to contribute approximately one-half of the anthropogenic increase in the absorption of the Earth's IR radiation. The world energy sector is responsible for an estimated 57% of future global warming when contributions from additional combustion-related pollutants are included. To stabilize atmospheric concentrations of carbon dioxide even at current levels, models suggest the need to reduce emission rates by 75%. An analysis of policy options shows that a combination of vastly improved energy efficiency strategies and carbon-free energy production technologies will be essential to even slowing global warming. This paper summarizes our knowledge of the greenhouse effect and its consequences, and examines the contribution that solar electricity and other renewables can make toward atmospheric stabilization goals. Some specific examples and strategies, which may accelerate the rate at which solar technologies can penetrate the market, will be given.