Three key molecules that trap heat in the atmosphere, known as greenhouse gases, are:

• Water vapor (H2O) : The most abundant greenhouse gas, it naturally occurs as part of the global water cycle and absorbs infrared radiation, trapping heat

• Carbon dioxide (CO2) : Released by natural processes and human activities like burning fossil fuels and deforestation, CO2 absorbs infrared radiation by causing its molecular bonds to vibrate, trapping heat that would otherwise escape into space

• Methane (CH4) : Emitted from natural sources such as wetlands and human activities like livestock digestion and fossil fuel extraction, methane is more effective than CO2 at trapping heat due to its molecular structure and vibrational modes

These gases absorb infrared radiation emitted by the Earth's surface, preventing some of this heat from escaping into space and thereby warming the atmosphere through the greenhouse effect