The cryosphere encompasses the Earth's snow and ice masses. It is a critical part of our planet's climate system, one that is especially at risk from climate change and global warming. The Cryosphere provides an essential introduction to the subject, written by one of the world's leading experts in Earth-system science. In this primer, glaciologist Shawn Marshall introduces readers to the cryosphere and the broader role it plays in our global climate system. After giving a concise overview, he fully explains each component of the cryosphere and how it works - seasonal snow, permafrost, river and lake ice, sea ice, glaciers, ice sheets, and ice shelves. Marshall describes how snow and ice interact with our atmosphere and oceans and how they influence climate, sea level, and ocean circulation. He looks at the cryosphere's role in past ice ages, and considers the changing cryosphere's future impact on our landscape, oceans, and climate. Accessible and authoritative, this primer also features a glossary of key terms, suggestions for further reading, explanations of equations, and a discussion of open research questions in the field.