Greenhouse gases (GHGs) are gases in the Earth's atmosphere that have the ability to trap and retain heat, leading to the greenhouse effect and contributing to global warming and climate change. The most common greenhouse gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases. Greenhouse gases are released into the atmosphere from various human activities, such as burning fossil fuels, deforestation, agriculture, and industrial processes.