This thoroughly revised and updated third edition focuses on the utilization of sustainable energy and mitigating climate change, serving as an introduction to physics in the context of societal problems. A distinguishing feature of the text is the discussion of spectroscopy and spectroscopic methods as a crucial means to quantitatively analyze and monitor the condition of the environment, the factors determining climate change, and all aspects of energy conversion. This textbook will be invaluable to students in physics and related subjects, and supplementary materials are available on a companion website.