ALBERT

Beschreibung: The application of biochar as a soil amendment to improve soil fertility has been suggested as a tool to reduce soil-borne CO 2 and non-CO 2 greenhouse gas emissions, especially nitrous oxide (N 2 O). Both lab and field trials have demonstrated N 2 O emission reduction by biochar amendment, but the long-term effect (〉1 year) has been questioned. Here we present results of a combined microcosm and field study using a powdered beech wood biochar from slow pyrolysis. The field experiment showed that both CO 2 and N 2 O emissions were still effectively reduced by biochar in the third year after application. However, biochar did not influence the biomass yield of sunflower for biogas production ( Helianthus annuus L.). Biochar reduced bulk density and increased soil aeration and thus reduced the water filled pore space (WFPS) in the field, but was also able to suppress N 2 O emission in the microcosms experiment conducted at constant WFPS. For both experiments, biochar had limited impact on soil mineral nitrogen speciation, but it reduced the accumulation of nitrite in the microcosms. Extraction of soil DNA and quantification of functional marker genes by qPCR showed that biochar did not alter the abundance of nitrogen-transforming bacteria and archaea in both field and microcosm experiments. In contradiction to previous experiments, this study demonstrates the long-term N 2 O emission suppression potential of a wood biochar and thus highlights its overall climate change mitigation potential. While a detailed understanding of the underlying mechanisms requires further research we provide evidence for a range of biochar-induced changes to the soil environment and their change with time that might explain the often observed N 2 O emission suppression. This article is protected by copyright. All rights reserved.

Beschreibung: Irrigation is not only vital for global food security, but also constitutes an anthropogenic land-use change, known to have strong effects on local hydrological and energy cycles. Using the Max Planck Institute for Meteorology's Earth System Model we show that related impacts are not confined regionally, but that possibly as much as 40% of the present-day precipitation in some of the arid regions in Eastern Africa are related to irrigation-based agriculture in Asia. Irrigation in South Asia also substantially influences the climate throughout Southeast Asia and China via the advection of water vapor and by altering the Asian monsoon. The simulated impact of irrigation on remote regions is sensitive to the magnitude of the irrigation-induced moisture flux. Therefore, it is likely that a future extension or decline of irrigated areas due to increasing food demand or declining fresh water resources will also affect precipitation and temperatures in remote regions.

Beschreibung: We examine how soil moisture variability and trends affect the simulation of temperature and precipitation extremes in six global climate models using the experimental protocol of the Global Land-Atmosphere Coupling Experiment of the Coupled Model Intercomparison Project, Phase 5 (GLACE-CMIP5). This protocol enables separate examinations of the influences of soil moisture variability and trends on the intensity, frequency and duration of climate extremes through to the end of the 21 s t century under a business-as-usual (RCP8.5) emission scenario. Removing soil moisture variability significantly reduces temperature extremes over most continental surfaces while wet precipitation extremes are enhanced in the tropics. Projected drying trends in soil moisture lead to increases in intensity, frequency, and duration of temperature extremes by the end of the 21 s t century. Wet precipitation extremes are decreased in the tropics with soil moisture trends in the simulations while dry extremes are enhanced in some regions, in particular the Mediterranean and Australia. However, the ensemble results mask considerable differences in the soil moisture trends simulated by the six climate models. We find that the large differences between the models in soil moisture trends, which are related to an unknown combination of differences in atmospheric forcing (precipitation, net radiation), flux partitioning at the land surface, and how soil moisture is parameterized, imply considerable uncertainty in future changes in climate extremes.

Beschreibung: The general circulation models used to simulate global climate typically feature resolution too coarse to reproduce many smaller scale processes, which are crucial to determining the regional responses to climate change. A novel approach to downscale climate change scenarios is presented which includes the interactions between the North Atlantic Ocean and the European shelves as well as their impact on the North Atlantic and European climate. The goal of this paper is to introduce the global ocean – regional atmosphere coupling concept and to show the potential benefits of this model system to simulate present day climate. A global ocean – sea ice – marine biogeochemistry model (MPIOM/HAMOCC) with regionally high horizontal resolution is coupled to an atmospheric regional model (REMO) and global terrestrial hydrology model (HD) via the OASIS coupler. Moreover, results obtained with ROM using NCEP/NCAR reanalysis and ECHAM5/MPIOM CMIP3 historical simulations as boundary conditions are presented and discussed for the North Atlantic and North European region. The validation of all the model components, i.e. ocean, atmosphere, terrestrial hydrology and ocean biogeochemistry is performed and discussed. The careful and detailed validation of ROM provides evidence that the proposed model system improves the simulation of many aspects of the regional climate, remarkably the ocean, even though some biases persist in other model components, thus leaving potential for future improvement. We conclude that ROM is a powerful tool to estimate possible impacts of climate change on the regional scale. This article is protected by copyright. All rights reserved.

Beschreibung: Abstract The forthcoming Surface Water and Ocean Topography (SWOT) satellite mission will provide global measurements of the free surface of large rivers, providing new opportunities for remote sensing‐derived estimates of river discharge in gaged and ungaged basins. SWOT discharge algorithms have been developed and benchmarked using synthetic data but remain untested on real‐world swath altimetry observations. We present the first discharge estimates from AirSWOT, a SWOT‐like airborne Ka‐band radar, using 6 days of measurements over a 40‐km segment of the Willamette River in Oregon, USA. The three evaluated discharge algorithms estimated discharge with normalized root‐mean‐square errors of 10–31% when compared with in situ gage data but were sensitive to an initial estimate of mean annual discharge. Our results show that these discharge algorithms provide reliable discharge estimates on remotely sensed data at SWOT‐like spatial scales while highlighting the need for further algorithm sensitivity tests.

Beschreibung: While increasing the terrestrial biomass is the most promising method to withdraw CO2 from the atmosphere, the long‐term storage of biogenic carbon plays a preponderant role for climate change mitigation. Biomass pyrolysis could convert sustainably produced biomass into solid (biochar), liquid (bio‐oil), and gaseous carbonaceous products, which allow long‐term storage in soils, biomaterials, and geological deposits. We review this new concept, now termed pyrolytic carbon capture and storage (PyCCS), which is expected to evolve into a decisive tool for future agriculture (biochar) and bio‐economy (biochar, bio‐oil, biofuels) serving climate change mitigation and the sustainable development goals simultaneously. Abstract The growth of biomass is considered the most efficient method currently available to extract carbon dioxide from the atmosphere. However, biomass carbon is easily degraded by microorganisms releasing it in the form of greenhouse gases back to the atmosphere. If biomass is pyrolyzed, the organic carbon is converted into solid (biochar), liquid (bio‐oil), and gaseous (permanent pyrogas) carbonaceous products. During the last decade, biochar has been discussed as a promising option to improve soil fertility and sequester carbon, although the carbon efficiency of the thermal conversion of biomass into biochar is in the range of 30%–50% only. So far, the liquid and gaseous pyrolysis products were mainly considered for combustion, though they can equally be processed into recalcitrant forms suitable for carbon sequestration. In this review, we show that pyrolytic carbon capture and storage (PyCCS) can aspire for carbon sequestration efficiencies of 〉70%, which is shown to be an important threshold to allow PyCCS to become a relevant negative emission technology. Prolonged residence times of pyrogenic carbon can be generated (a) within the terrestrial biosphere including the agricultural use of biochar; (b) within advanced bio‐based materials as long as they are not oxidized (biochar, bio‐oil); and (c) within suitable geological deposits (bio‐oil and CO2 from permanent pyrogas oxidation). While pathway (c) would need major carbon taxes or similar governmental incentives to become a realistic option, pathways (a) and (b) create added economic value and could at least partly be implemented without other financial incentives. Pyrolysis technology is already well established, biochar sequestration and bio‐oil sequestration in soils, respectively biomaterials, do not present ecological hazards, and global scale‐up appears feasible within a time frame of 10–30 years. Thus, PyCCS could evolve into a decisive tool for global carbon governance, serving climate change mitigation and the sustainable development goals simultaneously.