How it works
Sunlight, mostly visible light, passes through the atmosphere and warms the ground, which then radiates heat as infrared. Greenhouse gases—water vapor, carbon dioxide, methane, nitrous oxide—absorb that infrared and re-emit it in all directions, sending some back to the surface. That keeps Earth's average around 59°F (15°C); without it, the planet would average about 0°F (−18°C). The natural greenhouse effect is essential for life.
The enhanced effect and global warming
Burning fossil fuels and clearing forests have pushed CO₂ from about 280 ppm before industrialization to over 420 ppm, enhancing the effect. Svante Arrhenius first calculated CO₂-driven warming in 1896, and the IPCC's Sixth Assessment Report (2021) called human influence on warming "unequivocal." Positive feedbacks—more water vapor, melting ice reflecting less sunlight—amplify it. Over millions of years, plate tectonic processes like volcanism also shift atmospheric CO₂.
FAQ
- Are the greenhouse effect and global warming the same?
- No—the greenhouse effect is natural; global warming is the temperature rise from its human-driven enhancement.
- Which greenhouse gas is strongest?
- Water vapor is most abundant, CO₂ is the biggest human-added driver, and methane is far more potent per molecule.
Sources reviewed: 2026-10-26
References
- Arrhenius, S. (1896). On the influence of carbonic acid in the air upon the temperature of the ground. Philosophical Magazine, 41, 237–276.
- IPCC. (2021). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report. Cambridge University Press.
- NASA. Global Climate Change: Vital Signs of the Planet.