Long-term changes of hydrogen-containing species in the stratosphere

Understanding the 1% per year increase of stratospheric water vapour from 1954 to 2000 is a great challenge in atmospheric science. The increase is predominantly caused by long-term changes in transport of water vapour into the stratosphere and systematic increases of tropospheric methane levels. This paper gives a review on stratospheric water vapour changes for the 1980 and 2000 time period with emphasis on the contribution of methane oxidation. Predictions for 2050 indicate that likely increases of tropospheric methane levels will lead to an increase of upper stratospheric water vapour values of about 0.4 ppmv. A similar value is predicted as an upper limit of effects of a future hydrogen economy. (c) 2006 Elsevier Ltd. All rights reserved

Impact of a possible future global hydrogen economy on Arctic stratospheric ozone loss

The potential role of molecular hydrogen (H-2) as a future alternative energy carrier has generated widespread interest. The possible amount of additional hydrogen emission into the atmosphere in a hydrogen-based economy depends on future hydrogen production and leakage rates throughout the complete process chain. However, the expected emissions are highly uncertain. Based on the current literature an upper limit is estimated. Additional hydrogen emissions yield enhanced water vapor concentrations in the stratosphere which will have an impact on stratospheric temperatures and on polar ozone loss. Both stratospheric water vapor and ozone are important drivers of climate change. The potential environmental risks are described and assessed to be low compared to the environmental benefits

MOSES – A modelling tool for the analysis of scenarios of the European electricity supply system

Recent studies have shown that a transition of the current power supply system in Europe to a system almost entirely based on fluctuating Renewable Energy Sources (RES) by mid-century is possible. However, most of these scenarios require a significant amount of back-up power capacities to ensure the security of electricity supply. This would imply high additional investments and operating costs. Hence, alternative options should be investigated first. Here we present a first outlook of our simulation model MOSES which will be able to analyse different target states of the European electricity system in 2050. In this model long-term meteorological data series are used to optimise the capacity mix of RES in Europe. One of the main elements of our tool is a simplified electricity network. In addition, alternative options for reduction of additional back-up power like the expansion of the transmission grid, the use of demand-side management and/or the installation of over-capacities will be implemented. The results will be used to provide scientifically proven recommendations to policy makers for a reliable energy supply system in Europe based on Renewable Energy Sources

MOSES – A modelling tool for the analysis of scenarios of the European electricity supply system

Recent studies have shown that a transition of the current power supply system in Europe to a system almost entirely based on fluctuating Renewable Energy Sources (RES) by mid-century is possible. However, most of these scenarios require a significant amount of back-up power capacities to ensure the security of electricity supply. This would imply high additional investments and operating costs. Hence, alternative options should be investigated first. Here we present a first outlook of our simulation model MOSES which will be able to analyse different target states of the European electricity system in 2050. In this model long-term meteorological data series are used to optimise the capacity mix of RES in Europe. One of the main elements of our tool is a simplified electricity network. In addition, alternative options for reduction of additional back-up power like the expansion of the transmission grid, the use of demand-side management and/or the installation of over-capacities will be implemented. The results will be used to provide scientifically proven recommendations to policy makers for a reliable energy supply system in Europe based on Renewable Energy Sources

Impact of stratospheric water vapor enhancements caused by CH4 and H2O increase on polar ozone loss

Possible causes of a future increase in stratospheric H2O are increasing tropospheric methane levels and a rise in tropospheric H-2 due to leakages from a possible increased integration of hydrogen into the energy supply system. Here we quantify the direct chemical impact of potential future stratospheric H2O increases on Arctic ozone loss using the cold Arctic winter 2004/2005 as the basis for our study. We present simulations with the three-dimensional chemistry transport model CLaMS using enhanced stratospheric H2O values. Previous studies emphasized that increasing H2O concentrations cause stratospheric cooling, and some have suggested that this could significantly increase halogen-induced polar ozone loss. The impact of both increased stratospheric H2O values and decreased temperatures on simulated ozone depletion is investigated. Assuming an average increase of water vapor in the lower polar stratosphere of approximate to 0.58 ppmv (averaged over equivalent latitudes >= 65 degrees N, from 400-550 K potential temperature and from December to March) and in addition decreased temperatures (-0.2 K) yields at most 6.8 DU (approximate to 11 %) more accumulated ozone loss in mid-March for the Arctic polar winter 2004/2005 compared to the ozone loss for undisturbed conditions. The assumed H2O enhancement in future decades is in the range of current model predictions. Considering in addition the decrease of the future chlorine loading (-40 %) of enhanced H2O values (see above) yields at most 3.4 DU (10 %) of accumulated ozone loss in springtime compared to current H2O values. The impact of a potential future hydrogen economy alone (assuming an averaged increase of 0.18 ppmv H2O in the lower stratosphere) on springtime accumulated ozone loss is found to be negligible (at most 2.5 DU (4 %)) in this study

Sensitivity of Arctic ozone loss to stratospheric H2O

Likely causes of a future increase in stratospheric H2O are a rise in tropospheric CH4 and H-2 leakages from an increased integration of hydrogen into the energy supply system. Here we evaluate the impact of potential future stratospheric H2O increases on Arctic ozone loss by comparing ozone loss proxies based on two different mechanisms of chlorine activation. In particular, the H2O dependence of the volume of air is analyzed where temperatures are low enough to form nitric acid trihydrate, denoted as V-PSC, and for C1 activation on liquid sulfate aerosols, denoted as V-AC1. We show that V-AC1 increases faster than VPSC with increasing H2O mixing ratios in the altitude range of 400 K to 550 K potential temperature. As a consequence, the additional ozone column loss is expected to be most pronounced for cold winters and large H2O increases and to be significantly higher when V-AC1 is used as a proxy