A blanket of gases
How the air keeps the Earth warm.
Keeping heat in
On a cold night, a blanket keeps your body heat from escaping.
What might keep the Earth's heat from escaping into space?
What this lesson covers
The idea
The Earth's surface re-radiates absorbed sunlight as infrared; greenhouse gases such as CO2, CH4 and water vapour absorb this heat and keep it from escaping to space, keeping the Earth warm enough for life.
Keeping heat in
On a cold night, a blanket keeps your body heat from escaping.
What might keep the Earth's heat from escaping into space?
- Some gases in the air
- The Moon
- Nothing
Heat in, heat held
Press Next step.
Heat that stays
Greenhouse gases act like a blanket for the Earth's heat. Without the atmosphere, the Earth would be too cold for life to survive.
The Earth's surface re-radiates absorbed sunlight as infrared. Greenhouse gases such as CO₂, CH₄ and water vapour absorb this heat and keep it from escaping to space, keeping the Earth warm enough for life.
Notes
The surface re-radiates sunlight as infrared, and greenhouse gases (CO₂, CH₄, water vapour) absorb the heat and keep it from escaping, so the Earth stays warm enough for life.
Check yourself
In what form does the Earth's surface re-radiate absorbed sunlight?
Which of these is a greenhouse gas named in the chapter?
What do greenhouse gases do to the heat re-radiated from the surface?
What does the greenhouse effect do for life on the Earth?
- Gamma rays. Gamma rays are high energy radiation. The surface re-radiates absorbed sunlight in the infrared region.
- Infrared — correct. Yes!
- Ultraviolet. The surface re-radiates sunlight in the infrared region, not as UV.
- Nitrogen (N₂). The greenhouse gases named in the chapter are CO₂, CH₄ and water vapour.
- Argon. The greenhouse gases named in the chapter are CO₂, CH₄ and water vapour.
- Methane (CH₄) — correct. Yes!
- Absorb it, keeping it from escaping to space — correct. Yes!
- Send all of it straight out into space. Greenhouse gases absorb this heat and prevent it from escaping into space.
- Convert it into visible light. Greenhouse gases absorb the heat. The chapter does not say they turn it into light.
- Makes the Earth too cold for life. Without the atmosphere, the Earth would be too cold for life. The greenhouse effect keeps it warm enough.
- Keeps the Earth warm enough to support life — correct. Yes!
- Blocks harmful UV from reaching the Earth. Blocking harmful UV is the job of the ozone layer.