It starts at home? Climate policies targeting household consumption and behavioral decisions are key to low-carbon futures

Through their consumption behavior, households are responsible for 72% of global greenhouse gas emissions. Thus, they are key actors in reaching the 1.5 °C goal under the Paris Agreement. However, the possible contribution and position of households in climate policies is neither well understood, nor do households receive sufficiently high priority in current climate policy strategies. This paper investigates how behavioral change can achieve a substantial reduction in greenhouse gas emissions in European high-income countries. It uses theoretical thinking and some core results from the HOPE research project, which investigated household preferences for reducing emissions in four European cities in France, Germany, Norway and Sweden. The paper makes five major points: First, car and plane mobility, meat and dairy consumption, as well as heating are the most dominant components of household footprints. Second, household living situations (demographics, size of home) greatly influence the household potential to reduce their footprint, even more than country or city location. Third, household decisions can be sequential and temporally dynamic, shifting through different phases such as childhood, adulthood, and illness. Fourth, short term voluntary efforts will not be sufficient by themselves to reach the drastic reductions needed to achieve the 1.5 °C goal; instead, households need a regulatory framework supporting their behavioral changes. Fifth, there is a mismatch between the roles and responsibilities conveyed by current climate policies and household perceptions of responsibility. We then conclude with further recommendations for research and policy.     

Multidimensional upstream weighting for multiphase transport on general grids

The governing equations for multiphase flow in porous media have a mixed character, with both nearly elliptic and nearly hyperbolic variables. The flux for each phase can be decomposed into two parts: (1) a geometry- and rock-dependent term that resembles a single-phase flux; and (2) a mobility term representing fluid properties and rock–fluid interactions. The first term is commonly discretized by two- or multipoint flux approximations (TPFA and MPFA, respectively). The mobility is usually treated with single-point upstream weighting (SPU), also known as dimensional or donor cell upstream weighting. It is well known that when simulating processes with adverse mobility ratios, SPU suffers from grid orientation effects. An important example of this, which will be considered in this work, is the displacement of a heavy oil by water. For these adverse mobility ratio flows, the governing equations are unstable at the modeling scale, rendering a challenging numerical problem. These challenges must be addressed in order to avoid systematic biasing of simulation results. In this work, we present a framework for multidimensional upstream weighting for multiphase flow with buoyancy on general two-dimensional grids. The methodology is based on a dual grid, and the resulting transport methods are provably monotone. The multidimensional transport methods are coupled with MPFA methods to solve the pressure equation. Both explicit and fully implicit approaches are considered for time integration of the transport equations. The results show considerable reduction of grid orientation effects compared to SPU, and the explicit multidimensional approach allows larger time steps. For the implicit method, the total number of non-linear iterations is also reduced when multidimensional upstream weighting is used.     

Implications of recent sea level rise science for low-elevation areas in coastal cities of the conterminous U.S.A.

Recently published work estimates that global sea level rise (SLR) approaching or exceeding 1 m by 2100 is plausible, thus significantly updating projections by the Fourth Assessment of the Intergovernmental Panel on Climate Change. Furthermore, global greenhouse gas (GHG) emissions over the 21st century will not only influence SLR in the next ??90 years, but will also commit Earth to several meters of additional SLR over subsequent centuries. In this context of worsening prospects for substantial SLR, we apply a new geospatial dataset to calculate low-elevation areas in coastal cities of the conterminous U.S.A. potentially impacted by SLR in this and following centuries. In total, 20 municipalities with populations greater than 300,000 and 160 municipalities with populations between 50,000 and 300,000 have land area with elevations at or below 6 m and connectivity to the sea, as based on the 1 arc-second National Elevation Dataset. On average, approximately 9% of the area in these coastal municipalities lies at or below 1 m. This figure rises to 36% when considering area at or below 6 m. Areal percentages of municipalities with elevations at or below 1?C6 m are greater than the national average along the Gulf and southern Atlantic coasts. In contrast to the national and international dimensions of and associated efforts to curb GHG emissions, our comparison of low-elevation areas in coastal cities of the conterminous U.S.A. clearly shows that SLR will potentially have very local, and disproportionate, impacts.     

Pollen-based continental climate reconstructions at 6 and 21 ka: a global synthesis

Subfossil pollen and plant macrofossil data derived from ¹⁴C-dated sediment profiles can provide quantitative information on glacial and interglacial climates. The data allow climate variables related to growing-season warmth, winter cold, and plant-available moisture to be reconstructed. Continental-scale reconstructions have been made for the mid-Holocene (MH, around 6 ka) and Last Glacial Maximum (LGM, around 21 ka), allowing comparison with palaeoclimate simulations currently being carried out as part of the fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. The synthesis of the available MH and LGM climate reconstructions and their uncertainties, obtained using modern-analogue, regression and model-inversion techniques, is presented for four temperature variables and two moisture variables. Reconstructions of the same variables based on surface-pollen assemblages are shown to be accurate and unbiased. Reconstructed LGM and MH climate anomaly patterns are coherent, consistent between variables, and robust with respect to the choice of technique. They support a conceptual model of the controls of Late Quaternary climate change whereby the first-order effects of orbital variations and greenhouse forcing on the seasonal cycle of temperature are predictably modified by responses of the atmospheric circulation and surface energy balance.     

Thermal history and origin of the Tanzanian Craton from Pb isotope thermochronology of feldspars from lower crustal xenoliths

Common and radiogenic Pb isotopic compositions of plagioclase and anti-perthitic feldspars from granulite-facies lower crustal xenoliths from the Labait Volcano on the eastern margin of the Tanzanian Craton have been measured via laser ablation MC-ICP-MS. Common Pb in plagioclase and a single stage Pb evolution model indicate that the lower crust of the Tanzanian Craton was extracted from mantle having a ²³⁸U/²⁰⁴Pb of 8.1 ± 0.3 and a ²³²Th/²³⁸U of 4.3 ± 0.1 at 2.71 ± 0.09 Ga (all uncertainties are 2σ). Since 2.4 Ga, some orthoclase domains within anti-perthites have evolved with a maximum ²³⁸U/²⁰⁴Pb of 6 and ²³²Th/²³⁸U of 4.3. The spread in Pb isotopic composition in the anti-perthitic feldspars yields single crystal Pb–Pb isochrons of ～ 2.4 Ga, within uncertainty of U–Pb zircon ages from the same sample suite. The Pb isotopic heterogeneities imply that these granulites resided at temperatures < 600 °C in the lower crust of the Tanzanian Craton from ca. 2.4 Ga to the present. In concert with the chemistry of surface samples, mantle xenoliths, and lower crustal xenoliths, our data imply that the cratonic lithosphere in Tanzania formed ca. ～ 2.7 Ga, in a convergent margin setting, and has remained undisturbed since 2.7 Ga.     

Thermodynamic characterization of boltwoodite and uranophane: Enthalpy of formation and aqueous solubility

Boltwoodite and uranophane are uranyl silicates common in oxidized zones of uranium ore deposits. An understanding of processes that impact uranium transport in the environment, especially pertaining to the distribution of uranium between solid phases and aqueous solutions, ultimately requires determination of thermodynamic parameters for such crystalline materials. We measured formation enthalpies of synthetic boltwoodites, K(UO₂)(HSiO₄)·H₂O and Na(UO₂)(HSiO₄)·H₂O, and uranophane, Ca(UO₂)₂(HSiO₄)₂·5H₂O, by high temperature oxide melt solution calorimetry. We also studied the aqueous solubility of these phases from both saturated and undersaturated conditions at a variety of pH. The combined data permit the determination of standard enthalpies, entropies and Gibbs free energies of formation for each phase and analysis of its potential geological impact from a thermodynamic point of view.     

Temporal association of arc–continent collision,progressive magma contamination in arc volcanism and formation of gold-rich massive sulphide deposits on Wetar Island (Banda arc)

Whole-rock ⁸⁷Sr/⁸⁶Sr and δ¹⁸O analyses of volcanic rocks and ³He/⁴He analyses of sulphides and sulphates from mineralized rocks on Wetar, Indonesia indicate a variable contribution of assimilated crustal material or sediment sourced from the subducted Australian craton to the south. These new data support the idea of progressive source contamination with precisely dated events showing that Wetar Island hosts the most extreme examples of crustal assimilation in the region. The increased continental contamination occurs during the Pliocene (Zanclian to Piacenzian) during distinct magmatic events between 5 and 4 Ma, and at 2.4 Ma when ⁸⁷Sr/⁸⁶Sr ratios in unaltered lavas, with whole-rock δ¹⁸O values between 5.7 and 9.6‰, increase from 0.707484 to extreme radiogenic values of 0.711656.The earlier of these magmatic events is important in the generation of the hydrothermal systems responsible for the mineralization recorded on Wetar. Samples from this yield radiogenic ³He/⁴He ratios between 0.5 and 1.4 R/R_A, similar to the data from volcanic rocks on nearby Romang. The later magmatic event coincides with the arrival of the Australian Continental Margin at the subduction zone along the Banda arc. Progressive incorporation of continental-sourced components into the source region below the Wetar Island edifice coincides with the formation of gold-rich volcanogenic massive sulphide deposits hosted within the contaminated volcanic pile.     

Seasonal variation and tidal influences on estuarine use by bottlenose dolphins (Tursiops aduncus)

In order to show that dolphins use estuary habitats differently depending on the season and tidal state, possibly in response to prey distribution, temperature, risk of stranding and accessibility, Indo-Pacific bottlenose dolphins (Tursiops aduncus) were observed year-round during a 3-year study in the Clarence River estuary (CR) and Richmond River estuary (RR) in northern New South Wales, Australia. Peak dolphin sightings occurred during the spring season and one or 2 h prior to high tide. The spatial distribution of the dolphins in each estuary was analysed using the distance in kilometres that the dolphins travelled upstream with seasons and tidal phase as determinants. A General Linear Model showed that in the CR the dolphin spatial distribution in the estuary was not determined by season (F = 0.434, df = 3, P = 0.729) but was by tidal phase (F = 9.943, df = 3, P < 0.001) and the interaction between season and tidal phase (F = 3.398, df = 9, P < 0.002). However, in the RR the spatial distribution of the dolphin use of the estuary was not determined by either season (F = 1.647, df = 3, P = 0.194) or tidal phase (F = 0.302, df = 3, P = 0.824). In the CR, the spatial distribution of the dolphins was largest on high and flood tides. This pattern of spatial distribution may occur because the CR is a relatively shallow estuary and this increased spatial distribution may reflect a lower stranding risk and an increase in accessibility of shallow areas during periods of higher tide. These areas could also provide access to their preferred prey items of sea mullet (Mugil cephalus) and sand whiting (Sillago ciliata).     

Surface energy and water vapor fluxes observed in a desert plantation in central Iran

Summertime observations of surface radiation budget, energy balance and atmospheric surface layer meteorology were made on an arid valley floor planted with Haloxylon aphyllum to combat desertification in central Iran. The surface microclimate is characterized and compared with other arid regions and the role of ‘desert greening’ on surface fluxes is considered. A high surface albedo (0.265) and large longwave radiation loss produced relatively low net radiation. Energy partitioning was dominated by sensible and ground heat fluxes with opposing diurnal asymmetry governed by strong diurnal variability in eddy diffusivity. The Bowen ratio was 2.53, which fell inside the range of other vegetated arid surfaces. Surface temperature gradients were strong both in the atmospheric surface layer and in the substrate, with consistent lapse conditions by day and inversions at night. The wind regime included a moderate daytime regional wind which displayed Coriolis turning and weaker nocturnal slope flows. Actual evapotranspiration (1 mm dy⁻¹) was only a small fraction of potential evapotranspiration. The diurnal pattern of AET indicates strong stomatal control. The desert greening effect of Haloxylon plantations provided atmospheric water and reduced sensible heat flux by up to 40%.     

Reconstructing recent sedimentation in two urbanised coastal lagoons (NSW,Australia) using radioisotopes and geochemistry

In this study, we combined grain size and geochemical analyses with radioisotope analysis of lead-210 (²¹⁰Pb), caesium-137 (¹³⁷Cs) and radiocarbon (¹⁴C) ages to reconstruct the sedimentation history of two urbanised coastal lagoons in south-east Australia. Towradgi and Fairy Lagoons were both found to exhibit slow initial sedimentation of less than 1 mm year⁻¹ prior to anthropogenic influences. Land clearing in the catchments increased runoff and erosion in the creeks feeding into the estuaries, and has resulted in progradation of fluvial material into the estuarine systems with a marked increase in sedimentation to between 2 and 7 mm year⁻¹. The upper 20–50 cm of the sediment column in both lagoons contained elevated concentrations of heavy metals such as Pb, Cu, Ni and Zn. This pollution trend was found to be consistent with the history of industrialisation and urbanisation in the region, which expanded rapidly post World War 2. The total metal concentrations were consistent with other urbanised/industrialised estuaries around the world. Despite the fairly disturbed nature of these coastal lagoons, the use of ²¹⁰Pb, ¹³⁷Cs and ¹⁴C dating in combination with bulk geochemical analyses allowed detailed reconstruction of sedimentation history.