Soil carbon sequestration has been shown to be an important part of a portfolio of carbon sequestration strategies in the U.S. and Canada, and one that can be implemented at relatively low costs [McCarl and Schneider, 2001]. The purpose of this analysis is to estimate the soil carbon sequestration potential in the North America (Canada and United States) and its impact on net terrestrial CO₂ uptake over the period 1981-2000.

The paper presents major results of the terrestrial biota full carbon account (FCA) for a large region of Northern Eurasia based on a semi-empirical ecosystem-landscape approach and taking into account major requirements to a verified FCA. The average net ecosystem production (NEP) and net biome production (NBP) for the entire region are estimated for 2003 at 59 and 33 g C m^-2, respectively. It is shown that uncertainties of the regional FCA can be reliably estimated and decreased to an acceptable level if the information base and methodology used are based on a consistent systems approach.

To date there has been little systematic research on how carbon cycle scientific information will be used to support decisions at various scales.  There is therefore a strong need to begin to understand how carbon cycle science is currently being used, who potential users might be, and how to effectively engage stakeholders and scientists on the issue.  Many assumptions are being made about the scales and information that will be of most use to decision-makers.  Decisions and information flow do not necessarily translate between scales, and thus matching the scales between provision of scientific information and scale of decision-making is critical to effectively making information useful.  This paper will examine the ways in which carbon is being or may be managed by users at various scales, characterize decision making processes of those users, and discuss implications for carbon management and science policy.

We estimated the effects of initial vertical distribution of dissolved inorganic carbon (DIC) on storage efficiency of direct injection of CO₂ into the ocean. Our simulations shown that the storage efficiencies could be reduced up to 10% if a relative large droplet (30 mm in diameter) was injected at depth of 1500m. The storage efficiency of CO₂ ocean sequestration is strongly related with not only injection depth but also the initial CO₂ droplet diameter. With a given injection rate, the larger droplets injected will produce a dilute DIC plume and thus improve the acute biological impacts but a smaller storage effective due to droplet ascending.

A field experiment on the Swiss Plateau was designed to measure the greenhouse gas (GHG) budget of two parallel fields after conversion from arable crop rotation to cut grassland and managed either intensively or extensively. Measurements of N₂O fluxes with chambers and of CO₂ with eddy flux towers were complemented by estimates of C-imports (organic fertilizers) and C-exports (yield). The results indicate that newly established grassland plots act as a net GHG sink when management intensity (fertilization and cutting) is high, while conversion to extensive grasslands leads to an initial net loss of GHG.

At present, approximately half of anthropogenic CO₂ emissions are absorbed by the land and oceans [Jones and Cox, 2005], but climate changes may act to reduce this uptake, leading to higher CO₂ levels for a given emission scenario [Cox et al., 2000, Friedlingstein et al., 2005, in prep.]. Less attention has been paid to the potential impact of carbon cycle feedbacks on the emissions reductions required to achieve stabilisation (the so called “permissible emissions”), although this is arguably more pertinent to the issue of avoiding dangerous climate change in the context of the United Nations Framework Convention on Climate change.

During the past two centuries, human activities have undertaken a vast earth system modification of the carbon (C) cycle. Early during this period, humans have converted native vegetation to croplands. Such land use changes have mobilized massive amounts of C. During the past century, increased use of fossil energy sources, primarily coal and oil, have resulted in the rapid expansion of industry and technology throughout the world.  The resulting impact has been to greatly increase the atmospheric concentration of C dioxide (CO₂) to where in 2004 it is estimated to 375ppm, nearly 100 pm greater than the pre-industrial levels. Fossil fuel emissions and land use change have moved the global C cycle out of balance.

Iron fertilization has been proposed as a cheap, controllable, and environmentally benign method for removing carbon dioxide from the atmosphere. While this is in fact the case in simple, 3-box models of the carbon cycle, more realistic models show that these claims fall short of reality. The fact that the efficiency of iron fertilization depends on the long term fate of the added iron and on the carbon associated with it makes tracking the effects of iron fertilization much more difficult and expensive than has been asserted. Additionally, advection of low nutrient water away from iron-rich areas can result in lowering production remotely, with potentially serious consequences.

Different metrics to assess mitigation of global warming by carbon capture and storage are discussed. The climatic impact of capturing 30% of the anthropogenic carbon emission and its storage in the ocean or in a geological reservoir are evaluated for different stabilization scenarios using a reduced-form carbon cycle-climate model. The accumulated Global Warming Avoided (GWA) remains, after a ramp-up during the first ~50 years, in the range of 15 to 30% over the next millennium for deep ocean injection and for geological storage with annual leakage rates of up to about 0.001. For longer time scales, the GWA may approach zero or become negative for storage in a reservoir with even small leakage rates, accounting for the CO₂ associated with the energy penalty for carbon capture. For an annual leakage rate of 0.01, surface air temperature becomes higher than in the absence of storage after three centuries only.