Quantifying sediment storage in a high alpine valley (Turtmanntal,Switzerland)

The determination of sediment storage is a critical parameter in sediment budget analyses. But, in many sediment budget studies the quantification of magnitude and time‐scale of sediment storage is still the weakest part and often relies on crude estimations only, especially in large drainage basins (>100 km²). We present a new approach to storage quantification in a meso‐scale alpine catchment of the Swiss Alps (Turtmann Valley, 110 km²). The quantification of depositional volumes was performed by combining geophysical surveys and geographic information system (GIS) modelling techniques. Mean thickness values of each landform type calculated from these data was used to estimate the sediment volume in the hanging valleys and the trough slopes. Sediment volume of the remaining subsystems was determined by modelling an assumed parabolic bedrock surface using digital elevation model (DEM) data. A total sediment volume of 781·3×10⁶–1005·7×10⁶ m³ is deposited in the Turtmann Valley. Over 60% of this volume is stored in the 13 hanging valleys. Moraine landforms contain over 60% of the deposits in the hanging valleys followed by sediment stored on slopes (20%) and rock glaciers (15%). For the first time, a detailed quantification of different storage types was achieved in a catchment of this size. Sediment volumes have been used to calculate mean denudation rates for the different processes ranging from 0·1 to 2·6 mm/a based on a time span of 10 ka. As the quantification approach includes a number of assumptions and various sources of error the values given represent the order of magnitude of sediment storage that has to be expected in a catchment of this size. Copyright © 2009 John Wiley & Sons, Ltd.     

Searching for Added Value in Simulating Climate Extremes with a High-Resolution Regional Climate Model over Western Canada

We evaluate the capacity of a regional climate model to represent observed extreme temperature and precipitation events and also examine the impact of increased resolution, in an effort to identify added value in this respect. Two climate simulations of western Canada (WCan) were conducted with the Canadian Regional Climate Model (version 4) at 15 (CRCM15) and 45?km (CRCM45) horizontal resolution driven at the lateral boundaries by data from the European Centre for Medium-range Weather Forecasts (ECMWF) 40-year Reanalysis (ERA-40) for the period 1973–1995. The simulations were evaluated using the spline-interpolated dataset ANUSPLIN, a daily observational gridded surface temperature and precipitation product with a nominal resolution of approximately 10?km. We examine a range of climate extremes, comprising the 10th and 90th percentiles of daily maximum (TX) and minimum (TN) temperatures, the 90th percentile of daily precipitation (PR90), and the 27 core Climate Daily Extremes (CLIMDEX) indices.

Both simulations exhibit cold biases compared with observations over WCan, with the bias exacerbated at higher resolution, suggesting little added value for temperature overall. There are instances, however, of regional improvement in the spatial pattern of temperature extremes at the higher resolution of CRCM15 (e.g., the CLIMDEX index for the annual number of days when TX?>?25°C). The high-resolution simulations also reveal similarly localized features in precipitation (e.g., rain shadows) that are not resolved at the 45?km resolution. With regard to precipitation extremes, although both simulations generally display wet biases, CRCM15 features a reduced bias in PR90 in all seasons except winter. This improvement occurs despite the fact that spatial and interannual variability of PR90 in CRCM15 is significantly overestimated relative to both CRCM45 and ANUSPLIN. We posit that these characteristics are the result of demonstrable differences between corresponding topographical datasets used in the gridded observations and CRCM, the resulting errors propagated to physical variables tied to elevation and the beneficial effect of subsequent spatial averaging. Because topographical input is often discordant between simulations and gridded observations, it is argued that a limited form of spatial averaging may contribute added value beyond that which has already been noted in previous studies with respect to small-scale climate variability.     

Climate benefits of changing diet

Climate change mitigation policies tend to focus on the energy sector, while the livestock sector receives surprisingly little attention, despite the fact that it accounts for 18% of the greenhouse gas emissions and for 80% of total anthropogenic land use. From a dietary perspective, new insights in the adverse health effects of beef and pork have lead to a revision of meat consumption recommendations. Here, we explored the potential impact of dietary changes on achieving ambitious climate stabilization levels. By using an integrated assessment model, we found a global food transition to less meat, or even a complete switch to plant-based protein food to have a dramatic effect on land use. Up to 2,700 Mha of pasture and 100 Mha of cropland could be abandoned, resulting in a large carbon uptake from regrowing vegetation. Additionally, methane and nitrous oxide emission would be reduced substantially. A global transition to a low meat-diet as recommended for health reasons would reduce the mitigation costs to achieve a 450 ppm CO₂-eq. stabilisation target by about 50% in 2050 compared to the reference case. Dietary changes could therefore not only create substantial benefits for human health and global land use, but can also play an important role in future climate change mitigation policies.     

The need for national deep decarbonization pathways for effective climate policy

Constraining global average temperatures to 2 °C above pre-industrial levels will probably require global energy system emissions to be halved by 2050 and complete decarbonization by 2100. In the nationally orientated climate policy framework codified under the Paris Agreement, each nation must decide the scale and method of their emissions reduction contribution while remaining consistent with the global carbon budget. This policy process will require engagement amongst a wide range of stakeholders who have very different visions for the physical implementation of deep decarbonization. The Deep Decarbonization Pathways Project (DDPP) has developed a methodology, building on the energy, climate and economics literature, to structure these debates based on the following principles: country-scale analysis to capture specific physical, economic and political circumstances to maximize policy relevance, a long-term perspective to harmonize short-term decisions with the long-term objective and detailed sectoral analysis with transparent representation of emissions drivers through a common accounting framework or ‘dashboard’. These principles are operationalized in the creation of deep decarbonization pathways (DDPs), which involve technically detailed, sector-by-sector maps of each country’s decarbonization transition, backcasting feasible pathways from 2050 end points. This article shows how the sixteen DDPP country teams, covering 74% of global energy system emissions, used this method to collectively restrain emissions to a level consistent with the 2 °C target while maintaining development aspirations and reflecting national circumstances, mainly through efficiency, decarbonization of energy carriers (e.g. electricity, hydrogen, biofuels and synthetic gas) and switching to these carriers. The cross-cutting analysis of country scenarios reveals important enabling conditions for the transformation, pertaining to technology research and development, investment, trade and global and national policies.

Policy relevance

In the nation-focused global climate policy framework codified in the Paris Agreement, the purpose of the DDPP and DDPs is to provide a common method by which global and national governments, business, civil society and researchers in each country can communicate, compare and debate differing concrete visions for deep decarbonization in order to underpin the necessary societal and political consensus to design and implement short-term policy packages that are consistent with long-term global decarbonization.     

Reducing global GHG emissions by replicating successful sector examples: the ‘good practice policies’ scenario

This article shows the potential impact on global GHG emissions in 2030, if all countries were to implement sectoral climate policies similar to successful examples already implemented elsewhere. This assessment was represented in the IMAGE and GLOBIOM/G4M models by replicating the impact of successful national policies at the sector level in all world regions. The first step was to select successful policies in nine policy areas. In the second step, the impact on the energy and land-use systems or GHG emissions was identified and translated into model parameters, assuming that it would be possible to translate the impacts of the policies to other countries. As a result, projected annual GHG emission levels would be about 50 GtCO₂e by 2030 (2% above 2010 levels), compared to the 60 GtCO₂e in the ‘current policies’ scenario. Most reductions are achieved in the electricity sector through expanding renewable energy, followed by the reduction of fluorinated gases, reducing venting and flaring in oil and gas production, and improving industry efficiency. Materializing the calculated mitigation potential might not be as straightforward given different country priorities, policy preferences and circumstances.

Key policy insights

• Considerable emissions reductions globally would be possible, if a selection of successful policies were replicated and implemented in all countries worldwide.

• This would significantly reduce, but not close, the emissions gap with a 2°C pathway.

• From the selection of successful policies evaluated in this study, those implemented in the sector ‘electricity supply’ have the highest impact on global emissions compared to the ‘current policies’ scenario.

• Replicating the impact of these policies worldwide could lead to emission and energy trends in the renewable electricity, passenger transport, industry (including fluorinated gases) and buildings sector, that are close to those in a 2°C scenario.

• Using successful policies and translating these to policy impact per sector is a more reality-based alternative to most mitigation pathways, which need to make theoretical assumptions on policy cost-effectiveness.

     

Call For Papers

Call for Papers

Call For Papers     

Regional GHG reduction targets based on effort sharing: a comparison of studies

Over 40 studies that analyse future GHG emissions allowances or reduction targets for different regions based on a wide range of effort-sharing approaches and long-term concentration stabilization levels are compared. This updates previous work undertaken for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Regional reduction targets differ significantly for each effort-sharing approach. For example, in the Organisation for Economic Co-operation and Development (OECD) 1990 region, new proposals that emphasize the equity principles of responsibility, capability, and need, and those based on equal cumulative per capita emissions (carbon budgets), lead to relatively stringent emissions reduction targets. In order to reach a low concentration stabilization level of 450?ppm CO₂e, the allowances under all effort sharing approaches in OECD1990 for 2030 would be approximately half of the emissions of 2010 with a large range, roughly two-thirds in the Economies in Transition (EIT), roughly at the 2010 emissions level or slightly below in Asia, slightly above the 2010 level in the Middle East and Africa and well below the 2010 level in Latin America. For 2050, allowances in OECD1990 and EIT would be a fraction of today's emissions, approximately half of 2010 emission levels in Asia, and possibly less than half of the 2010 level in Latin America.

Policy relevance

The concept of equity and the stringency of future national GHG reduction targets are at the heart of the current debate on the new international climate change agreement to be adopted in 2015. Policy insights gained from an analysis of over 40 studies, which have quantitatively analysed the proposed GHG reduction targets, are presented. It is found that the outcome of effort-sharing approaches is often largely determined by the way the equity principle is implemented and that the distributional impacts of such approaches can be significantly different depending on the criteria used, the stabilization level and shape of the global emissions pathway. However, the current literature only covers a small proportion of the possible allocation approaches. There should thus be an in-depth modelling comparison to ensure consistency and comparability of results and inform decision making regarding the reduction of GHG emissions.