Greenhouse gases (GHGs) are gases in the Earths atmosphere that trap heat, causing the Earths surface to warm up. They absorb the wavelengths of radiation that the Earth emits, resulting in the greenhouse effect. The most abundant GHG is water vapor, but other GHGs include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases.

The accumulation of GHGs since the Industrial Revolution has accelerated the greenhouse effect, causing global warming and climate change. Human activities, such as the burning of fossil fuels, deforestation, and agriculture, have increased atmospheric concentrations of GHGs, particularly CO2 and methane.

Each GHG has a different effect on climate change, depending on its abundance in the atmosphere and its Global Warming Potential (GWP). GWP is a measure of how much energy the emissions of 1 ton of a gas will absorb over a given period of time, typically a 100-year time horizon, relative to the emissions of 1 ton of CO2. Gases with a higher GWP absorb more energy, per ton emitted, than gases with a lower GWP, and thus contribute more to warming Earth.