What is the greenhouse effect?
The greenhouse effect is the way gases in Earth's atmosphere trap heat from the Sun, keeping the planet warm enough for life. Adding more of these gases makes the planet warmer.
Sunlight passes through the atmosphere and warms Earth's surface. The warm surface then gives off heat as infrared radiation. Greenhouse gases, such as water vapor, carbon dioxide, methane and nitrous oxide, absorb some of this heat and send part of it back toward the ground, like a blanket around the planet.
Without the natural greenhouse effect, Earth's average temperature would be about minus 18 degrees Celsius instead of about 15 degrees. Oceans would freeze and most life could not exist. So the greenhouse effect itself is natural and essential.
Why it matters now
Burning coal, oil and gas and clearing forests has raised carbon dioxide levels in the air by about 50 percent since the 1800s. This has strengthened the greenhouse effect and warmed the planet by about 1.2 to 1.3 degrees Celsius, causing rising seas, melting ice and more extreme heat waves.
Did You Know?
Venus has a runaway greenhouse effect. Its thick carbon dioxide atmosphere makes it the hottest planet in the solar system, at about 465 degrees Celsius.