Origins of differences in climate sensitivity, forcing and feedback in climate models

We diagnose climate feedback parameters and CO₂ forcing including rapid adjustment in twelve atmosphere/mixed-layer-ocean (“slab”) climate models from the CMIP3/CFMIP-1 project (the AR4 ensemble) and fifteen parameter-perturbed versions of the HadSM3 slab model (the PPE). In both ensembles, differences in climate feedbacks can account for approximately twice as much of the range in climate sensitivity as differences in CO₂ forcing. In the AR4 ensemble, cloud effects can explain the full range of climate sensitivities, and cloud feedback components contribute four times as much as cloud components of CO₂ forcing to the range. Non-cloud feedbacks are required to fully account for the high sensitivities of some models however. The largest contribution to the high sensitivity of HadGEM1 is from a high latitude clear-sky shortwave feedback, and clear-sky longwave feedbacks contribute substantially to the highest sensitivity members of the PPE. Differences in low latitude ocean regions (30°N/S) contribute more to the range than those in mid-latitude oceans (30–55°N/S), low/mid latitude land (55°N/S) or high latitude ocean/land (55–90°N/S), but contributions from these other regions are required to account fully for the higher model sensitivities, for example from land areas in IPSL CM4. Net cloud feedback components over the low latitude oceans sorted into percentile ranges of lower tropospheric stability (LTS) show largest differences among models in stable regions, mainly due to their shortwave components, most of which are positive in spite of increasing LTS. Differences in the mid-stability range are smaller, but cover a larger area, contributing a comparable amount to the range in climate sensitivity. These are strongly anti-correlated with changes in subsidence. Cloud components of CO₂ forcing also show the largest differences in stable regions, and are strongly anticorrelated with changes in estimated inversion strength (EIS). This is qualitatively consistent with what would be expected from observed relationships between EIS and low-level cloud fraction. We identify a number of cases where individual models show unusually strong forcings and feedbacks compared to other members of the ensemble. We encourage modelling groups to investigate unusual model behaviours further with sensitivity experiments. Most of the models fail to correctly reproduce the observed relationships between stability and cloud radiative effect in the subtropics, indicating that there remains considerable room for model improvements in the future.     

Stakeholder perspectives on use, trade, and conservation of medicinal plants in the Rasuwa district of central Nepal

People’s livelihood in several Himalayan regions largely depends on collection, use, and trade of medicinal plants. Traditional use is generally not a problem, but commercial gathering of selected species to meet increasing national and international demand can result in over-exploitation. Sustainable management of medicinal plants requires a clear understanding of the respective roles, responsibilities and viewpoints of the various stakeholders involved. Through personal interviews and group discussions, this study aimed at investigating the views of two stakeholder groups on use, trade and conservation of medicinal plants in the Rasuwa district of Nepal. Local people and district and national organizations agreed that medicinal plants are collected for a combination of commercial and personal uses. Perceptions on market availability differed significantly: 100 % of the respondents from district and national organizations saw markets as easily available, against only 36 % for local people. This could explain why medicinal plants were perceived by local people to contribute less to income generation than to livelihood improvement. Different viewpoints were also expressed concerning the status of medicinal plants in the district: 81 % of the respondents from district and national organizations considered that medicinal plants were threatened, compared to only 28 % for local people. Despite this disparity, both stakeholder groups agreed upon potential threats to medicinal plants: over-harvesting; habitat loss due to land-use change and deforestation; and over-grazing by livestock. Several challenges were identified regarding sustainable management of medicinal plants, such as ambiguous policies; lack of resources, information and infrastructures; habitat degradation; and over-exploitation. Despite these challenges, respondents agreed that the medicinal plants sector offers huge opportunities in the Rasuwa district, given resource availability, community awareness and motivation, and the priority given to the sector by governments and other agencies. Proper collaboration, communication and coordination among stakeholders are needed to grab these opportunities.     

Future demographic change and its interactions with migration and climate change

This paper examines global demographic change as a driver of migration within the context of anticipated climate change. It begins by briefly considering some theoretical formulations which relate demographic change and migration. It then considers evolving global demographic trends and discusses some of their potential impacts upon migration. It is shown that there is a close spatial coincidence between demographic and climate change “hotspots” that will influence migration in complex ways. It then turns to the complex interaction between demographic change, environmental change and migration, both in the past and potential developments in the future. It concludes with a discussion of the potential impacts of future trends and their policy implications.     

Dienerian (Early Triassic) ammonoids from the Candelaria Hills (Nevada, USA) and their significance for palaeobiogeography and palaeoceanography

A well-preserved ammonoid fauna of Early Dienerian age has long been known from the lower portion of the Candelaria Formation in the old Candelaria silver mining district in Mineral and Esmeralda Counties, Nevada, but for a number of reasons, this fauna has never been studied in detail nor illustrated. Previous authors assigned this ammonoid fauna to the Early Dienerian Proptychites candidus Zone of Canada. In reality, it more closely resembles the Tethyan faunas than the higher palaeolatitude Canadian faunas, thus indicating the presence of some degree of equatorial faunal exchange between opposite sides of the Panthalassic Ocean during Early Dienerian time. It also indicates the onset of a provincialism, which contrasts with the cosmopolitan Griesbachian faunas. A rigorous taxonomic analysis of the Candelaria fauna allows us to differentiate the following ten species, which include two new species and one new genus (Mullericeras nov. gen.) belonging to the new family Mullericeratidae: Ambites lilangensis (Krafft, 1909), Ambites aff. radiatus (Brühwiler, Brayard, Bucher and Guodun, 2008), Ussuridiscus sp. indet., ??Koninckites?? aff. kraffti Spath, 1934, Mullericeras spitiense (Krafft, 1909), Mullericeras fergusoni nov. sp., Mullericeras sp. indet., Proptychites haydeni (Krafft, 1909), Proptychites pagei nov. sp., Vavilovites sp. indet. and Parahedenstroemia kiparisovae Shigeta and Zakharov, 2009. This Early Dienerian fauna correlates with the Ambites fauna known from the base of the Ceratite Marls in the Salt Range and from the base of the ??Meekoceras?? beds in Spiti (northern Gondwanian margin). The fauna also permits the precise dating of a shelfal anoxic episode on the equatorial North American margin. This anoxic event correlates in time with similar palaeoceanographic changes in the southern Tethys, which indicates that the Early Triassic biotic recovery was at least partly shaped by such discrete, short events rather than by pervasive and lingering adverse environmental conditions.     

Geochemical variations in Andean basaltic and silicic lavas from the Villarrica-Lanin volcanic chain (39.5° S): an evaluation of source heterogeneity,fractional crystallization and crustal assimilation

At 39.5° S in the southern volcanic zone of the Andes three Pleistocene-recent stratovolcanoes, Villarrica, Quetrupillan and Lanin, form a trend perpendicular to the strike of the Andes, 275 to 325 km from the Peru-Chile trench. Basalts from Villarrica and Lanin are geochemically distinct; the latter have higher incompatible element abundances and La/Sm but lower Ba/La and alkali metal/La ratios. These differences are consistent with our previously proposed models involving: a) a west to east decrease in an alkali metal-rich, high Ba/La slab-derived component which causes an across strike decrease in degree of melting; or b) a west to east increase in the contamination of subduction-related magma by enriched subcontinental lithospheric mantle. Silicic and mafic lavas from the stratovolcanoes have overlapping Sr, Nd and O isotopic ratios. Silicic lavas also have geochemical differences that parallel those of their associated basalts, e.g., rhyolite from Villarrica has lower La/Sm and incompatible element contents than high-SiO₂ andesite from Lanin. At each volcano the most silicic lavas can be modelled by closed system fractional crystallization while andesites are best explained by magma mixing. Apparently crustal contamination was not an important process in deriving the evolved lavas. Basaltic flows from small scoria cones, 20–35 km from Villarrica volcano have high incompatible element contents and low Ba/La, like Lanin basalts, but trend to higher K/Rb (356–855) and lower ⁸⁷Sr/ ⁸⁶Sr (0.70361–0.70400) than basalts from either stratovolcano. However all basalts have similar Nd, Pb and O isotope ratios. The best explanation for the unique features of the cones is that the sources of SVZ magmas, e.g., slab-derived fluids or melts of the subcontinental lithospheric mantle, have varying alkali metal and radiogenic Sr contents. These heterogeneities are not manifested in stratovolcano basalts because of extensive subcrustal pooling and mixing. This model is preferable to one involving crustal contamination because it can account for variable Sr isotope ratios and uniform Nd and Pb isotope ratios among the basalts, and the divergence of the cones from across-strike geochemical trends defined by the stratovolcanoes.     

Propagation of positional error in 3D GIS: estimation of the solar irradiation of building roofs

While error propagation in GIS is a topic that has received a lot of attention, it has not been researched with 3D GIS data. We extend error propagation to 3D city models using a Monte Carlo simulation on a use case of annual solar irradiation estimation of building rooftops for assessing the efficiency of installing solar panels. Besides investigating the extension of the theory of error propagation in GIS from 2D to 3D, this paper presents the following contributions. We (1) introduce varying XY/Z accuracy levels of the geometry to reflect actual acquisition outcomes; (2) run experiments on multiple accuracy classes (121 in total); (3) implement an uncertainty engine for simulating acquisition positional errors to procedurally modelled (synthetic) buildings; (4) perform the uncertainty propagation analysis on multiple levels of detail (LODs); and (5) implement Solar3Dcity – a CityGML-compliant software for estimating the solar irradiation of roofs, which we use in our experiments. The results show that in the case of the city of Delft in the Netherlands, a 0.3/0.6 m positional uncertainty yields an error of 68 kWh/m²/year (10%) in solar irradiation estimation. Furthermore, the results indicate that the planar and vertical uncertainties have a different influence on the estimations, and that the results are comparable between LODs. In the experiments we use procedural models, implying that analyses are carried out in a controlled environment where results can be validated. Our uncertainty propagation method and the framework are applicable to other 3D GIS operations and/or use cases. We released Solar3Dcity as open-source software to support related research efforts in the future.     

Automatic conversion of IFC datasets to geometrically and semantically correct CityGML LOD3 buildings

Although the international standard CityGML has five levels of detail (LODs), the vast majority of available models are the coarse ones (up to LOD2, i.e. block‐shaped buildings with roofs). LOD3 and LOD4 models, which contain architectural details such as balconies, windows and rooms, rarely exist because, unlike coarser LODs, their construction requires several datasets that must be acquired with different technologies, and often extensive manual work is needed. In this article we investigate an alternative to obtaining CityGML LOD3 models: the automatic conversion from already existing architectural models (stored in the IFC format). Existing conversion algorithms mostly focus on the semantic mappings and convert all the geometries, which yields CityGML models having poor usability in practice (spatial analysis, for instance, is not possible). We present a conversion algorithm that accurately applies the correct semantics from IFC models and that constructs valid CityGML LOD3 buildings by performing a series of geometric operations in 3D. We have implemented our algorithm and we demonstrate its effectiveness with several real‐world datasets. We also propose specific improvements to both standards to foster their integration in the future.     

Mid-Holocene lateral collapse of Antuco volcano (Chile): debris avalanche deposit features,emplacement dynamics,and impacts

Antuco (37.4°S, 71.4°W; Chile) is a dominantly basaltic stratovolcano whose original?~?3300 m altitude main cone experienced a catastrophic sector collapse at?~?7.1 cal ka BP, producing a volcanic debris avalanche deposit (VDAD) with hummocky surface and?~?6.4 km³ of volume. We carried out geological studies of its debris avalanche deposit, which was distributed to the W and displays a longitudinal facies transformation from edifice’s megablocks and block to mixed facies in distal areas (up to 25 km from the scar). Our observations support the behavior of the avalanche beginning as a translational slide, and then as plug flow when confined within the Laja River valley. Clay abundance and high content of hydrothermally altered material may suggest active participation of water; flow velocities are estimated to?~100 m s^?1. We primarily identify the steep-sided flanks of the cone, and hydrothermal alteration promoted the edifice instability, while basement seismogenic structures may have ultimately triggered the landslide. Subsequent landslide-led events include the transformation of the volcanic activity with explosive eruptions producing a sequence of dilute pyroclastic density currents (PDCs) ending?~3.4 ky BP, and extensive lava effusion rapidly reconstructing the collapsed edifice. Moreover, the Antuco VDAD also blocked the natural output of the Laja Lake, increasing its level by?~200 m and then triggering cataclysmic outburst floods by dam rupture, preserved as high-energy alluvial beds with ages between 2.8 and 1.7 ky BP. The Antuco constitutes an excellent example of a critical chain of events initiated by a stratovolcano lateral collapse and warns for detailed hazard investigations to better comprehend its related impacts.

     

Can climate variability information constrain a hydrological model for an ungauged Costa Rican catchment?

Long‐term hydrological data are key to understanding catchment behaviour and for decision making within water management and planning. Given the lack of observed data in many regions worldwide, such as Central America, hydrological models are an alternative for reproducing historical streamflow series. Additional types of information—to locally observed discharge—can be used to constrain model parameter uncertainty for ungauged catchments. Given the strong influence that climatic large‐scale processes exert on streamflow variability in the Central American region, we explored the use of climate variability knowledge as process constraints to constrain the simulated discharge uncertainty for a Costa Rican catchment, assumed to be ungauged. To reduce model uncertainty, we first rejected parameter relationships that disagreed with our understanding of the system. Then, based on this reduced parameter space, we applied the climate‐based process constraints at long‐term, inter‐annual, and intra‐annual timescales. In the first step, we reduced the initial number of parameters by 52%, and then, we further reduced the number of parameters by 3% with the climate constraints. Finally, we compared the climate‐based constraints with a constraint based on global maps of low‐flow statistics. This latter constraint proved to be more restrictive than those based on climate variability (further reducing the number of parameters by 66% compared with 3%). Even so, the climate‐based constraints rejected inconsistent model simulations that were not rejected by the low‐flow statistics constraint. When taken all together, the constraints produced constrained simulation uncertainty bands, and the median simulated discharge followed the observed time series to a similar level as an optimized model. All the constraints were found useful in constraining model uncertainty for an—assumed to be—ungauged basin. This shows that our method is promising for modelling long‐term flow data for ungauged catchments on the Pacific side of Central America and that similar methods can be developed for ungauged basins in other regions where climate variability exerts a strong control on streamflow variability.