Carbon dioxide is an important gas in Earth’s environment. In the atmosphere it serves as a greenhouse gas that works to trap and hold heat near the surface of the planet. The process of limestone formation removes carbon dioxide from the atmosphere and stores it away for long periods of time. This process has been occurring for millions of years – producing enormous volumes of stored carbon dioxide. When these rocks are weathered, used to neutralize acids, heated to make cement or metamorphosed severely, some of their carbon dioxide is released and returned to the atmosphere. All of these processes of limestone formation and destruction have an impact on Earth’s climate.