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# The Greenhouse Effect

The picture shows, in a simplified way, how the Greenhouse Effect increases as carbon dioxide (CO2) levels rise in the atmosphere.

1. The greenhouse effect.  Cartoon by Julia Heres.

#### Explanation of the picture:

1. Burning down long lived forests adds carbon dioxide to the air.
2. Exhaust gases contain large amounts of CO2.
3. CO2 spreads throughout the atmosphere.
4. Ultra-violet radiation from the Sun enters our atmosphere.
5. The sun's radiation is absorbed by the ground and ...
6. ... the warm surface emits heat (infra-red radiation).
7. This infra-red radiation is absorbed by greenhouse gases such as CO2 and the heat is trapped in the lower atmosphere.
8. The air near the ground becomes warmer.

The Greenhouse Effect is a natural process, without it the Earth would be too cold for us to live on.  Humans have dramatically increased the concentrations of greenhouse gases, such as carbon dioxide, in the air.  This means more and more infra-red radiation coming from the surface of the Earth is trapped close to the ground and, as a result, the air temperature rises.

EXPERIMENT:

You can simulate the Greenhouse Effect with this little experiment.

#### What you need:

- a cardboard box

- a piece of glass large enough to cover one side of the box

- 2 electric thermometers

- a sunny day

#### Instructions:

Put the box outside in the sun on a sunny day. Place one thermometer inside the box and the other one next to the box. Now cover the top of the box with the glass. After 15 minutes, compare the temperatures of both thermometers.

2a. Temperature inside the box.
2b. Temperature outside the box.
(picture taken by Sarah Ancot)

#### CAN YOU ANSWER THE FOLLOWING QUESTIONS?

1. Which thermometer shows the highest temperature and why?

2. Have another look at the cartoon above and complete the following text.

……………………… - frequency rays from the Sun penetrate the glass.

At the bottom of the box they are ……………………and the box warms up.

This warmth is sent back into the air as ………………………radiation.

The glass prevents the ………… from leaving the box.

The air in the box becomes .......................... .

These are the missing words:  infra-red, ultra-violet, heat, warmer, absorbed.

3. Which processes emit CO2 into the atmosphere.

How can  some of these processes be prevented or reduced?