A Review of Forest Carbon Sequestration Cost Studies: A Dozen Years of Research

Researchers have been analyzing the costs of carbon sequestration for approximately twelve years. The purpose of this paper is to critically review the carbon sequestration cost studies of the past dozen years that have evaluated the cost-effectiveness of the forestry option. Several conclusions emerge. While carbon sequestration cost studies all contain essentially the same components they are not comparable on their face due to the inconsistent use of terms, geographic scope, assumptions, program definitions, and methods. For example, there are at least three distinct definitions for a `ton of carbon' that in turn lead to significantly different meanings for the metric `dollars per ton of carbon'. This difference in carbon accounting further complicates comparison of studies. After adjusting for the variation among the studies, it appears that carbon sequestration may play a substantial role in a global greenhouse gas emissions abatement program. In the cost range of 10 to 150 dollars per ton of carbon it may be possible to sequester 250 to 500 million tons per year in the United States, and globally upwards of 2,000 million tons per year, for several decades. However, there are two unresolved issues that may seriously affect the contribution of carbon sequestration to a greenhouse gas mitigation program, and they will likely have counteracting effects. First, the secondary benefits of agricultural land conversion to forests may be as great as the costs. If that is the case, then the unit costs essentially disappear, making carbon sequestration a no-regrets strategy. In the other direction, if leakage is a serious issue at both the national and international levels, as suggested by some studies, then it may occur that governments will expend billions of dollars in subsidies or other forms of incentives, with little or no net gain in carbon, forests or secondary benefits. Preliminary results suggest that market interactions in carbon sequestration program analyses require considerably more attention. This is especially true for interactions between the forest and agricultural land markets and between the wood product sink and the timber markets.     

Response of reindeer and caribou to human activities

Petroleum and mineral exploration and extraction, hydroelectric development, atmospheric transport of contaminants, timber harvesting and tourism are increasing worldwide, especially in the Arctic. This development may adversely affect populations of reindeer/caribou ( Rangifer tarandus ) which are the basis of subsistence economies for northern indigenous peoples. Our purpose is to present a survey of the literature that has investigated the response of reindeer/caribou to human activities. Individuals and groups of reindeer/caribou: 1) move away from point sources of disturbance; 2) increase activity and energy expenditure near disturbance; 3) delay crossing or fail to cross linear structures; 4) shift away from areas of extensive and intensive development; and 5) are killed by collisions with vehicles and by hunting along roads. Cows and calves during the calving season are the most easily disturbed group. Bulls in general and all reindeer/caribou during insect harassment are least likely to avoid development areas. Estimation of the proportion of a population that is exposed to disturbance and the implications of this exposure to annual energy budgets, survival and productivity of reindeer/caribou has received little attention. Future advances in understanding the implications of human disturbance to reindeer/caribou will require cumulative effects assessment at annual, population and regional scales. Although some level of cumulative effect is likely, clear separation of cumulative effects of development from natural variation in caribou habitat use and demography will be difficult.     

Cross-section for the dissociative photoionization of hydrogen by 584 Å radiation: The formation of protons in the Jovian ionosphere

The cross-section for dissociative photoionization of hydrogen by 584 Å radiation has been measured, yielding a value of 5 × 10^?20 cm². The process can be explained as a transition from the $\text{X}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ ground state to a continuum level of the $\text{X}{}^2\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ ionized state of H₂ The branching ratio for proton (H⁺) vs molecular ion (H₂⁺) production at this energy is 8 × 10^?3. This process is quite likely an important source of protons in the Jovian ionosphere near altitudes where peak ionization rates are found.     

A Holocene East Asian winter monsoon record at the southern edge of the Gobi Desert and its comparison with a transient simulation

Climate Dynamics - The East Asian winter monsoon (EAWM) exhibits significant variability on intraseasonal, interannual, and interdecadal time scales and the variability can be extended to Holocene...     

Model support for forcing of the 8.2 ka event by meltwater from the Hudson Bay ice dome

Previous model experiments of the 8.2 ka event forced by the drainage of Lake Agassiz often do not produce climate anomalies as long as those inferred from proxies. In addition to the Agassiz forcing, there is new evidence for significant amounts of freshwater entering the ocean at 8.2 ka from the disintegration of the Laurentide ice sheet (LIS). We use the Community Climate System Model version 3 (CCSM3) to test the contribution of this additional meltwater flux. Similar to previous model experiments, we find that the estimated freshwater forcing from Lake Agassiz is capable of sustaining ocean and climate anomalies for only two to three decades, much shorter than the event duration of ~150 years in proxies. Using new estimates of the LIS freshwater flux (~0.13 Sv for 100 years) from the collapse of the Hudson Bay ice dome in addition to the Agassiz drainage, the CCSM3 generates climate anomalies with a magnitude and duration that match within error those from proxies. This result is insensitive to the duration of freshwater release, a major uncertainty, if the total volume remains the same. An analysis of the modeled North Atlantic freshwater budget indicates that the Agassiz drainage is rapidly transported out of the North Atlantic while the LIS contribution generates longer-lasting freshwater anomalies that are also subject to recirculation by the subtropical gyre back into the North Atlantic. Thus, the meltwater flux originating from the LIS appears to be more important than the Agassiz drainage in generating 8.2 ka climate anomalies and is one way to reconcile some model-data discrepancies.