This monograph provides a scientific understanding of two major scientific problems of global concern, from the perspective of a physicist who seeks theories with great simplicity and superior predictive capacity. The book reviews the establishment of two theories of atmospheric ozone depletion and global climate change and provides a comprehensive overview of the author's work, including significant discoveries and pioneering contributions, such as the discoveries of dissociative electron transfer reactions of chlorofluorocarbons (CFCs) adsorbed on ice surfaces, the strong correlation between CFCs and global surface temperature, and the tropical ozone hole; the proposals of the cosmic-ray-driven electron-induced-reaction (CRE) theory for ozone depletion and the CFC theory for modern global warming and developments of them into complete quantitative theories enabling analytical calculations; the prediction and observation of 11-year cyclic variations of the Antarctic ozone hole; the first prediction from a quantitative model to observe a long-term global cooling that started in October 2023, which precisely agrees with measured global mean surface temperatures to date.Unlike conventional atmospheric and climate models, the theoretical models presented are built on robust observations and fundamental physics, using no adjustable parameters. The CRE and CFC theories are unique models that can quantitatively reproduce both the 11-year cyclic variation of the Antarctic ozone hole over the past four solar cycles and the Antarctic surface temperature change since 1850 with an uncertainty of 10% or less.This book is self-contained and unified in presentation. It may be used as an advanced book by graduate students and even ambitious undergraduates in physics, chemistry, environmental and climate sciences. It is also suitable for non-expert readers and policy makers who wish to have an overview of the sciences behind atmospheric ozone depletion and global climate change.