Impact of two potential policy options on atmospheric chemistry and climate: Hydrogen economy and low-GWP alternatives to ozone depleting substances.

摘要

The fingerprint of human activities on the composition of Earth's atmosphere is manifest. It is now well recognized that the changes in the atmospheric composition due to human activities have resulted in changes in several aspects of the environment, e.g., attenuation of the ozone layer due to emissions of ozone-depleting substances, climate change due to greenhouse gas emissions, and air pollution due to fossil fuel combustion. This research analyzes the impacts of two potential future policy options, (1) hydrogen economy and (2) low-GWP (Global Warming Potential) alternatives to hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs), on the composition of the atmosphere, on environment, on climate and on stratospheric ozone.;This research is accomplished by using state-of-the-art numerical models that represents detailed physical and chemical processes of the atmosphere with cutting-edge knowledge, together with specifically developed scenarios. This methodology can provide policymakers with prospective and insightful knowledge essential to effectively tackling the environmental issues caused by human activities.;This research gives a comprehensive analysis of the impacts of a future (2050) hydrogen economy on atmospheric environment. The uncertainties in the evolution paths of the world are bounded by the IPCC SRES high emission A1FI and low emission B1 scenarios. The atmospheric impacts of an internal combustion engine type hydrogen economy are analyzed for the first time in this research, as well as a fuel cell type hydrogen economy. The impacts of a future hydrogen economy analyzed based on global model simulations in this research include: changes in atmospheric hydrogen budget, effectiveness in improving air quality in different regions of the world, changes in the oxidative power of the atmosphere and the climate implication, and stability of the ozone layer. Air quality improvement in a hydrogen economy for the contiguous United States is analyzed based on regional air quality model simulations with finer resolution. It is found that hydrogen economy can improve air quality, provide opportunities to mitigate climate change without significantly harming stability of the ozone layer.;This research evaluates atmospheric lifetimes and GWP values for six unsaturated halogenated hydrocarbons, which are potential low-GWP alternatives to HFCs and HCFCs, using a three-dimensional global climate-chemistry model and a radiative transfer model. It is found that the alternative compounds have lifetimes less than a month and GWPs less than 5, orders of magnitude smaller than the long-lived HFCs. This research also analyzes the inadequacies of the simple estimation approach, which is used in several prior published studies, for very short-lived substances (VSLS). A rationale of evaluating GWPs for VSLS using three-dimensional atmospheric models is presented.