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In this paper, we propose a space-time dynamic model for describing the temporal evolution of greenhouse gas concentration in the atmosphere. We use this dynamic model to develop an optimal control strategy for reduction of atmospheric pollutants. We prove the existence of optimal policies subject to control constraints. Further, we present necessary conditions of optimality using which one can determine such policies. A convergence theorem for computation of the optimal policies is also presented. Simulation results illustrate removal of greenhouse gas using the optimal policies. [ABSTRACT FROM AUTHOR]

Xinjiang is a typical arid and semi-arid Mountain basin system, which make the regional ecosystem extremely fragile. Studying the influence of climate on vegetation is conducive to qualitatively analyze the change trend of vegetation coverage in this region. Therefore, utilizing vegetation coverage and main meteorological elements (temperature, precipitation, relative humidity, sunshine hours) data in Xinjiang province, this paper carried out the influence of multiple meteorological elements on vegetation coverage changes, and constructed a model of the impact of multiple meteorological elements on the growing season vegetation coverage based on random forest. The model can better simulate the vegetation coverage in 2017 and 2018, with an average error of 0.027, in consequence it can well forecast whether the vegetation is high-density or low-density in this area. Correlation analysis and variable importance show that the critical meteorological factors affecting vegetation cover change are relative humidity and sunshine hours, accounting for 73% of the vegetation coverage area. The results are helpful to understand how meteorological factors affect the vegetation coverage, and then provide a theoretical reference for the construction of ecological security in Xinjiang. [ABSTRACT FROM AUTHOR]

The arrival of the hydrogen (H2) economy has been the subject of many studies. Earlier articles were over-optimistic about the timing and extent of global H2 uptake, and predicted private vehicles as leading the way to a H2 economy. The recent strong rise in the global electric vehicle fleet has inevitably led to a reassessment of the prospects for H2, at least for transport. This review paper examines how researchers over recent decades have envisaged how the H2 economy would arrive, and why it was desirable, or even inevitable; it also looks at the future prospects for the H2 economy. The key findings are as follows: ? Among the leading energy forecasting bodies, particularly the International Energy Agency (IEA), even the most optimistic scenarios predict under 10% H2 penetration by 2050. ? IEA forecasts are very optimistic about the prospects for the introduction of carbon dioxide removal technologies and growth of dispatchable sources of low-carbon energy. ? More realistic IEA forecasts would increase the need for the growth of intermittent energy sources such as wind and solar. The subsequent requirement for energy storage would in turn help the case for H2 adoption. ? No new technologies are on the horizon to decisively tip the balance in favor of H2. ? It is concluded that a global H2 economy is still distant, but it could arise in energy-poor countries such as Japan and South Korea, and it could find a niche in freight transport. [ABSTRACT FROM AUTHOR]

Planet Earth is simultaneously approaching a number of ecological and resource limits. The resulting uncertainties will heavily impact future energy choices, both the level of primary energy used globally and the shares of fossil, renewable and nuclear fuels in the energy mix. This paper reviews the possible futures for the various types of renewable energy. To be viable, all potential energy sources must be assessed on their energy return on energy invested (energy return). Given that renewable energy RE growth is considered important for sustainability reasons, renewable energy must be assessed on its ecologically sustainable or 'green' energy return, which includes the energy costs of ecosystem maintenance as input energy costs. The green energy return is accordingly much lower than the conventional value, so that ecologically sustainable renewable energy is unlikely to deliver anything near existing global energy use. The paper further argues that such constraints on renewable energy growth rates mean it cannot be a timely response to global climate change. The paper concludes that energy reductions will be essential, mainly in high energy use countries. [ABSTRACT FROM AUTHOR]

Over the years, Ghana has invested considerable effort and resources together with international partners to develop the energy sector and to mainstream energy low carbon pathways into national development plans. Low carbon development (LCD) provides a good opportunity, of not only building upon earlier energy and climate change local processes and structures but also help to mainstream low carbon agenda in economic activities and national development plans. For this to work however, require efficient institutions and effective institutional arrangements. Based on extensive literature analysis, personal communications and inputs from stakeholders, the paper highlights the key institutional arrangements, their interactions, challenges and proffers recommendations for improvements. To improve energy and low carbon development effort from the perspectives of institutional structures, would require, clearer institutional mandates, continuous improvements in institutional coordination (intra and inter), capacity and skills development, sustained visibility of the essence of energy and LCD at high political levels as well as engagement by civil societies. Equally important are the issues of finance, data availability and quality, monitoring and evaluation. [ABSTRACT FROM AUTHOR]

Health Impact Assessment (HIA) is a decision support tool intended to present timely, evidence--based recommendations to decision makers in all sections of society in order to accentuate potential positive health and well-being impacts (and mitigate potential negative impacts) of policies, plans (including local and neighbourhood plans), programmes and projects (including infrastructure and local development proposals), in order to reduce health inequalities/disparities. HIA is a well established and proven means of linking research evidence from public health and the environmental sciences with equitable decision making processes at all levels, from local to global. It may also provide a platform for examination of research proposals to strengthen the impact statement therein, identifying potential for future public benefit. This paper highlights some of the main drivers for a timely re-emphasis on the use of best scientific evidence and systematic HIA to inform decision making for future public benefit, citing the example of air pollution. [ABSTRACT FROM AUTHOR]