Greenhouses gases, such as carbon dioxide, trap heat in the atmosphere and regulate our climate. These gases exist naturally, but humans add more carbon dioxide by burning fossil fuels for energy (coal, oil, and natural gas) and by clearing forests. Greenhouse gases act like a blanket. The thicker the blanket, the warmer our planet becomes. At the same time, the Earth’s oceans are also absorbing some of this extra carbon dioxide, making them more acidic and less hospitable for sea life.