41 Atmosphere and Climate-Low

Atmosphere and Climate Written by Karen de Seve

Introduction Look up at the sky. There's a very thin shield around Earth that you can't see. It's called the atmosphere. It contains the air we breathe and our weather. The shield protects us from the harmful rays of the Sun. It helps keep our planet warm. It makes life on Earth possible. In this book, you will learn about Earth's atmosphere. You will learn about weather over short and long periods of time. You'll also learn what makes up the atmosphere and how it is changing.

Earth's Invisible Shield The atmosphere is like a blanket. It protects and warms Earth's surface. It rises more than 700 kilometers (430 mi.) above Earth's surface. All the gases needed for life are in the atmosphere. The two main ones are nitrogen and oxygen. There are also smaller amounts of argon, carbon dioxide (CO2), and water vapor We need oxygen the most. Without oxygen, life as we know it could not exist.

Gases are made up of small particles called molecules. Gravity pulls the molecules toward Earth and packs them together. This blanket of gas molecules creates air pressure. The air pressure at the bottom of the atmosphere is fairly high. The air pressure farther up in the atmosphere is much, much lower.

You do not usually feel air pressure. The pressure is the same inside and outside your body. But when you take off in an airplane or drive up a mountain, you go higher in the atmosphere. The air pressure is less there. As the air pressure outside drops, the air pressure inside your ears stays the same. The air pushes out from your ears and makes a popping sound. Do You Know? Air pressure drops as you climb higher. If you climb high enough, the air is very spread out. You will need extra oxygen in order to breathe.

Layers of Atmosphere The atmosphere around Earth is divided into five layers. We live in the lowest layer— the troposphere. Earth's weather forms and changes in this layer. The stratosphere is the next layer. In this layer is the ozone layer. It protects us from the Sun's harmful rays. When people release certain gases at Earth's surface, the gases can float up and break down ozone. Then the ozone cannot absorb harmful rays as well. The mesosphere is the middle layer in which most meteors burn up. Spacecraft orbit in the thermosphere. The exosphere is the outermost layer.