What is The largest carbon source on earth?

The largest carbon source on Earth is the ocean, which holds about 38,000 billion metric tons of carbon in the form of dissolved carbon dioxide and organic matter. Additionally, terrestrial ecosystems, particularly forests and soil, also store significant amounts of carbon. However, when considering carbon emissions, fossil fuel reserves, such as coal, oil, and natural gas, represent a major source of carbon that can be released into the atmosphere when burned.