Syllabus Edition
First teaching 2015
Last exams 2025
Greenhouse Effect
Written by: Alistair Marjot
Reviewed by: Bridgette Barrett
The Greenhouse Effect
What is the Greenhouse Effect?
The Sun emits energy in the form of solar radiation (including visible light and ultraviolet rays) that enters the Earth’s atmosphere
Some thermal energy is reflected from the Earth's surface
Most thermal energy is absorbed and re-emitted back from the Earth’s surface
This energy passes through the atmosphere where some thermal energy passes straight through and is emitted into space
But some thermal energy is absorbed by greenhouse gases such as carbon dioxide, methane and water vapour, and is re-emitted in all directions
These gases act like a blanket, allowing sunlight to pass through but preventing a significant amount of the infrared radiation from escaping back into space
This reduces the thermal energy lost into space and traps it within the Earth’s atmosphere, keeping the Earth warm
This process is known as the greenhouse effect
The greenhouse effect is a naturally occurring phenomenon
The greenhouse effect is important to ensure that Earth is warm enough for life
If it were not for the insulating effect of greenhouse gases, Earth would see similar dramatic temperature fluctuations to its neighbouring planets
Without the greenhouse effect, the average temperature would be much colder, making the planet uninhabitable
Greenhouse gases absorb the radiation that is re-emitted from the Earth's surface, trapping it in the atmosphere
Examiner Tips and Tricks
Don't get confused - the greenhouse effect is a natural process and is necessary for life on Earth. The accelerated or enhanced greenhouse effect refers to the changes in the greenhouse effect (mostly due to human activity) that are commonly referred to as global warming. This is discussed further in 7.2.2!
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