A greenhouse gas is a type of gas that absorbs and emits radiation within the thermal infrared range. This means that these gases trap heat in the atmosphere, similar to how a greenhouse traps warmth for plants growing inside it. Common examples of greenhouse gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and water vapor (H2O). These gases are released into the atmosphere through various human activities, such as burning fossil fuels or deforestation. The increase in greenhouse gas concentrations has been linked to global warming and climate change.