A positive feedback loop makes an existing process speed up while a negative feedback loop decreases the impact of an existing process. A source emits carbon dioxide and other greenhouse gases while a sink retain and stores. However, with climate change a sink can possibly become a source. Carbon, which is a basic unit of life, is stored in various parts of the atmosphere including the ocean. However, when carbon dioxide dissolves in seawater, carbonic acid is formed, which is harmful to marine organism and the marine ecosystem. In the 21st century, scientists are concerned about the escalating the positive feedback loop of carbon dioxide. If _business as usual continues, many catastrophes predicted by scientists could occur.