A low-carbon society: global visions,pathways, and challenges

The feasibility of two low-carbon society (LCS) scenarios, one with and one without nuclear power and carbon capture and storage (CCS), is evaluated using the AIM/Enduse[Global] model. Both scenarios suggest that achieving a 50% emissions reduction target (relative to 1990 levels) by 2050 is technically feasible if locally suited technologies are introduced and the relevant policies, including necessary financial transfers, are appropriately implemented. In the scenario that includes nuclear and CCS options, it will be vital to consider the risks and acceptance of these technologies. In the scenario without these technologies, the challenge will be how to reduce energy service demand. In both scenarios, the estimated investment costs will be higher in non-Annex I countries than in Annex I countries. Finally, the enhancement of capacity building to support the deployment of locally suited technologies will be central to achieving an LCS.

Policy relevance

Policies to reduce GHG emissions up to 2050 are critical if the long-term target of stabilizing the climate is to be achieved. From a policy perspective, the cost and social acceptability of the policy used to reduce emissions are two of the key factors in determining the optimal pathways to achieve this. However, the nuclear accident at Fukushima highlighted the risk of depending on large-scale technologies for the provision of energy and has led to a backlash against the use of nuclear technology. It is found that if nuclear and CCS are used it will be technically feasible to halve GHG emissions by 2050, although very costly. However, although the cost of halving emissions will be about the same if neither nuclear nor CCS is used, a 50% reduction in emissions reduction will not be achievable unless the demand for energy service is substantially reduced.     

Correlations between oxygen-isotopic composition and petrologic setting in a coarse-grained Ca, Al-rich inclusion

Oxygen-isotopic compositions in conjunction with petrologic investigation have been determined for a coarse-grained type B2 Ca, Al-rich inclusion (CAI) from the reduced CV3 Vigarano using secondary ion mass spectrometry. The oxygen-isotopic compositions of minerals are distributed along the carbonaceous chondrite anhydrous mineral line indicating mixing between ¹⁶O-rich and ¹⁶O-poor nebular components. The O-isotopic heterogeneities among and within minerals in the CAI interior indicate that CAI formation started in an ¹⁶O-rich nebula and subsequently continued in an ¹⁶O-poor nebula. ¹⁶O-rich signatures of melilite and fassaite in the Wark-Lovering rim and of olivine of the accretionary rim indicate that the nebular environment during formation of the CAI returned to an ¹⁶O-rich composition after processing in an ¹⁶O-poor nebula. These O-isotopic variations in the CAI support multiple heating events in the solar nebula and indicate that the nebular environments fluctuated from ¹⁶O-rich to ¹⁶O-poor and back to ¹⁶O-rich compositions during the formation of a single CAI.     

The stemflow of trees in a Bornean lowland tropical forest

Stemflow volume generation in lowland tropical forests was measured over a 1‐year period in the Malaysian state of Sarawak. The stemflow volume generated by 66 free‐standing trees with a diameter at breast height (DBH) over 1 cm and a tree height over 1 m were measured daily in a representative 10 m × 10 m plot of the forest. Throughfall in the plot was also measured using 20 gauges in a fixed position. Of the 2292 mm of total rainfall observed during the year‐long period, stemflow accounted for 3·5%, throughfall for 82% and there was an interception loss of 14·5%. Understory trees (DBH < 10 cm) played an important role in stemflow generation, producing 77% of the overall stemflow volume and 90% during storms with less than 20 mm of rainfall. Also, owing to their efficiency at funneling rainfall or throughfall water received by their crowns, some understory trees noticeably reduced the catches of the throughfall gauges situated under the reach of their crown areas. During storms producing greater than 20 mm of rainfall, 80% of the total stemflow occurred; trees with a large DBH or height and for which the ratio between crown's diameter and depth is less than 1, tended to generate more stemflow volume in these storms. Mean areal stemflow as a fraction of rainfall in this lowland tropical forest was 3·4%, but may range from 1–10% depending upon the proportion of trees that are high or poor stemflow yielders. Trees with DBH greater than 10 cm were likely to contribute less than 1% of the 3·4% mean areal stemflow in the forest. Copyright © 2004 John Wiley & Sons, Ltd.     

A conceptual hydrologic model for a forested Carolina bay depressional wetland on the Coastal Plain of South Carolina,USA

This paper describes how climate influences the hydrology of an ephemeral depressional wetland. Surface water and groundwater elevation data were collected for 7 years in a Coastal Plain watershed in South Carolina USA containing depressional wetlands, known as Carolina bays. Rainfall and temperature data were compared with water‐table well and piezometer data in and around one wetland. Using these data a conceptual model was created that describes the hydrology of the system under wet, dry, and drought conditions. The data suggest this wetland operates as a focal point for groundwater recharge under most climate conditions. During years of below‐normal to normal rainfall the hydraulic gradient indicated the potential for groundwater recharge from the depression, whereas during years of above‐normal rainfall, the hydraulic gradient between the adjacent upland, the wetland margin, and the wetland centre showed the potential for groundwater discharge into the wetland. Using high‐resolution water‐level measurements, this groundwater discharge condition was found to hold true even during individual rainfall events, especially under wet antecedent soil conditions. The dynamic nature of the hydrology in this Carolina bay clearly indicates it is not an isolated system as previously believed, and our groundwater data expand upon previous hydrologic investigations at similar sites which do not account for the role of groundwater in estimating the water budget of such systems. Copyright © 2007 John Wiley & Sons, Ltd.     

A unified model for bedform development and equilibrium under unidirectional,oscillatory and combined‐flows

The development of bedforms under unidirectional, oscillatory and combined‐flows results from temporal changes in sediment transport, flow and morphological response. In such flows, the bedform characteristics (for example, height, wavelength and shape) change over time, from their initiation to equilibrium with the imposed conditions, even if the flow conditions remain unchanged. These variations in bedform morphology during development are reflected in the sedimentary structures preserved in the rock record. Hence, understanding the time and morphological development in which bedforms evolve to an equilibrium stage is critical for informed reconstruction of the ancient sedimentary record. This article presents results from a laboratory flume study on bedform development and equilibrium development time conducted under purely unidirectional, purely oscillatory and combined‐flow conditions, which aimed to test and extend an empirical model developed in past work solely for unidirectional ripples. The present results yield a unified model for bedform development and equilibrium under unidirectional, oscillatory and combined‐flows. The experimental results show that the processes of bedform genesis and growth are common to all types of flows, and can be characterized into four stages: (i) incipient bedforms; (ii) growing bedforms; (iii) stabilizing bedforms; and (iv) fully developed bedforms. Furthermore, the development path of bedform; growth exhibits the same general trend for different flow types (for example, unidirectional, oscillatory and combined‐flows), bedform size (for example, small versus large ripples), bedform shape (for example, symmetrical or rounded), bedform planform geometry (for example, two‐dimensional versus three‐dimensional), flow velocities and sediment grain sizes. The equilibrium time for a wide range of bed configurations was determined and found to be inversely proportional to the sediment transport flux occurring for that flow condition.     

Post-seismic Effects of an M 7.2 Earthquake and Microseismicity in an Abandoned, Flooded, Deep Mine

—?An M 7.2 earthquake took place 67?km southeast of an abandoned mine containing flooded, vertical ore veins at depth of 1?km. Multidisciplinary monitoring of the unweathered country rock within the mine was carried out for a distance of about one kilometer. The M 7.2 earthquake was followed by significant post-seismic changes in strain and tilt of ～10^?6, with a self-potential of ～10?mV, and an increase in the water level in the mine of about 10?cm/day. These phenomena continued for several months before returning to pre-earthquake levels. Coseismic elastic deformations were too small to account for the observed post-seismic changes, and have different senses in strain and tilt from the observed post-seismic changes. The contractions in strain and the changes in the electric self-potential and water-elevation rate strongly suggest an increase in pore pressure. An increase in microseismic activity (M?M 7.2 earthquake.     

Resting cells of microorganisms in the 20–100 μm fraction of marine sediments in an Antarctic coastal area

We investigated the morphological features, vertical sinking fluxes, and number densities of the resting cells of ice-associated microorganisms in the 20–100 μm fraction of natural marine sediments collected from ice-covered and ice-free areas around Syowa Station, Lützow-Holm Bay, East Antarctica. We identified the resting cells of various taxonomic groups, including the spores of a diatom, cysts of three dinoflagellates, cysts of five oligotrich ciliates, and the eggs of a mesozooplankton. This is the first report of oligotrich ciliate cysts from Antarctic waters. The resting spores of Thalassiosira australis (diatom), cysts of Polarella glacialis (dinoflagellate), and egg type 1 sink to the bottom sediment during summer. Our results suggest that some planktonic and ice-associated microorganisms in Antarctic coastal areas send their resting cells to the bottom sediments as seed populations for the following generation.     

Great earthquake at 7.3 ka inferred from tsunami deposits in the Sukumo Bay area,Southwestern Japan

Tsunami deposits in Kyushu Island, Southwestern Japan, have been attributed to the 7.3 ka Kikai caldera eruption, but their origin has not been confirmed. We analyzed an 83-cm-thick Holocene event deposit in the SKM core, obtained from incised valley fill in the coastal lowlands near Sukumo Bay, Southwestern Shikoku Island. We confirmed that the event deposit contains K-Ah volcanic ash from the 7.3 ka eruption. The base of the event deposit erodes the underlying inner-bay mud, and the deposit contains material from outside the local terrestrial and marine environment, including angular quartz porphyry from a small inland exposure, oyster shell debris, and a coral fragment. Benthic foraminifers and ostracods in the deposit indicate various habitats, some of which are outside Sukumo Bay. The sand matrix contains low-silica volcanic glass from the late stage of the Kikai caldera eruption. We also documented the same glass in an event deposit in the MIK1 core, from the incised Oyodo River valley in the Miyazaki Plain on Southeastern Kyushu. These two 7.3 ka tsunami deposits join other documented examples that are widely distributed in Southwestern Japan including the Bungo Channel and Beppu Bay in Eastern Kyushu, Tachibana Bay in Western Kyushu, and Zasa Pond on the Kii Peninsula as well as around the caldera itself. The tsunami deposits near the caldera have been divided into older and younger 7.3 ka tsunami deposits, the younger ones matching the set of widespread deposits. We attribute the younger 7.3 ka tsunami deposits to a large tsunami generated by a great interplate earthquake in the Northern part of the Ryukyu Trench and (or) the Western Nankai Trough just after the late stage of the Kikai caldera eruption and the older 7.3 ka tsunami deposits to a small tsunami generated by an interplate earthquake or Kikai caldera eruption.     

North Arch volcanic fields near Hawaii are evidence favouring the restite‐root hypothesis for the origin of hotspot swells

A pronounced regional bathymetric swell is a common feature of oceanic hotspot volcanism. Recently, the hypothesis of a buoyant sublithospheric swell‐root has been favoured, the root being either a ‘refracted plume’ of hot, buoyant and hence low‐viscosity plume material embedded within surrounding higher viscosity asthenosphere, or a ‘restite‐root’ composed of hot and more viscous residues to hotspot melt‐extraction from the hottest central portion of the upwelling plume. In this article, we present numerical experiments that show that these two scenarios predict different flow and melting patterns whenever the plume passes beneath an obliquely oriented fracture zone where the base of the overriding lithosphere changes in thickness. We find that the restite‐root hypothesis predicts an asymmetric spatial pattern of persistent ‘arch volcanism’ strikingly similar to that found in the Hawaiian chain surrounding the Molokai Fracture Zone. In contrast, the ‘refracted plume’ hypothesis predicts more chaotic patterns quite different from the off‐chain pattern of Hawaiian volcanism.     

Temporal variations in the abundance and sinking flux of diatoms under fast ice in summer near Syowa Station, East Antarctica

To investigate the fate of ice algae released from sea ice, we investigated the abundance, species composition, and sinking flux of diatoms in the water column under fast ice near Syowa Station, Antarctica during the summer of 2005/2006. The diatom assemblage in the water column consisted of chain-forming planktonic species, in contrast to the under-ice assemblage dominated by pennate species reported from this site in the past; this dissimilarity suggests the presence of an unconsolidated platelet ice layer under the congelation ice, within which planktonic species can bloom. Among the dominant diatoms, Porosira pseudodenticulata and Pseudo-nitzschia cf. turgiduloides were dominant in the water column, and their water column stocks were higher than their mass sedimentation. These species apparently maintain their populations in the surface layer, as their production remains in the water column. In contrast, Fragilariopsis kerguelensis and Thalassiosira australis were scarce in the water column but rich in the flux, indicating active sinking and export of their production to the benthic ecosystem. This distinction in buoyancy control and sinking characteristics of the dominant diatoms on release from the fast ice influences the diatom species composition and carbon flow under the ice.