Carbon dioxide

To understand climate change, we can look to Venus and Mars, both surrounded by carbon dioxide—the main greenhouse gas. On Venus, CO₂ traps enough heat to keep the surface at 850°F, while on Mars, a much thinner layer still warms the planet by about 40 degrees. Greenhouse gases work by trapping infrared energy: when the Sun heats Earth’s surface, most infrared escapes through simple gases like oxygen and nitrogen, but CO₂ and water vapor absorb and re-radiate it, sending some back toward the ground. This process keeps Earth warmer and explains why cloudy nights are warmer than clear ones—the same physics behind climate change.