Greenhouse effect

The idea

Gases like carbon dioxide in a planet's atmosphere trap heat by absorbing the radiation the planet gives off after the Sun warms it; this greenhouse effect makes Venus hotter than Mercury and keeps Earth's temperature just right.

Hottest planet

Mercury is closer to the Sun than Venus. But Venus is the hottest planet.

Why is Venus hotter than Mercury?

• Its thick atmosphere traps heat
• It is closer to the Sun
• It has no atmosphere

Trap the heat

Press Next step.

Heat trapped by gases

Venus is the hottest planet not because it is closest to the Sun but because its thick atmosphere traps heat. On Earth too, gases like carbon dioxide trap heat by absorbing the radiation given off by the Earth after the Sun warms it. The greenhouse effect helps to keep Earth just warm enough.

Gases like carbon dioxide trap heat by absorbing the radiation a planet gives off after the Sun warms it. This is the greenhouse effect. It makes Venus hotter than Mercury and keeps Earth's temperature just right.

Notes

The greenhouse effect: gases such as carbon dioxide trap heat by absorbing radiation.

Check yourself

Venus is the hottest planet because …

The air on Venus is almost entirely …

Gases like carbon dioxide trap heat by …

On Earth the greenhouse effect helps to …

• it is the closest to the Sun. Mercury is closer, but Venus is hotter.
• its thick atmosphere traps heat — correct. Yes!
• it has no atmosphere. Venus has a thick atmosphere.
• oxygen. Venus's air is almost entirely carbon dioxide.
• nitrogen. Venus's air is almost entirely carbon dioxide.
• carbon dioxide — correct. Yes!
• absorbing the radiation given off by the planet — correct. Yes!
• reflecting all sunlight away. They absorb radiation given off by the planet.
• making clouds only. They trap heat by absorbing radiation.
• make it hotter than Venus. It maintains just the right temperature.
• keep the temperature just right — correct. Yes!
• remove the atmosphere. The greenhouse effect needs the atmosphere.