The greenhouse effect is the process by which certain atmospheric gases (water vapor, carbon dioxide, methane, nitrous oxide, and others) absorb infrared radiation emitted by the Earth’s surface and re-emit it in all directions, including back toward the surface. This trapping of heat warms the planet beyond what its distance from the sun alone would produce. Without the natural greenhouse effect, Earth’s average surface temperature would be roughly -18°C rather than the ~15°C that has sustained complex life.
The anthropogenic intensification of the greenhouse effect is the mechanism of climate change. Burning fossil fuels, deforestation, and industrial agriculture have increased atmospheric concentrations of greenhouse gases — CO₂ from ~280 ppm (pre-industrial) to over 420 ppm (2024), with methane and nitrous oxide rising proportionally. This additional radiative forcing traps more heat, raising global temperatures and destabilizing climate systems through cascading feedback loops.
The physics is not disputed in any scientifically meaningful sense. The greenhouse effect was first described by Joseph Fourier (1824), experimentally demonstrated by Eunice Newton Foote (1856) and John Tyndall (1859), and quantified by Svante Arrhenius (1896). What remains contested is not the mechanism but the political response.